CBSE Class 10 Final Revision of Term 1 Examination

CHAPTER-1 : CHEMICAL REACTIONS AND EQUATIONS • A chemical equation is a symbolic representation that describes a chemical reaction in terms of symbol and formulae. • A chemical reaction is the transformation of chemical substance called reactants into another chemical substance called products. In a chemical reaction, only rearrangement of atoms takes place. • The substances which take part in a chemical reaction are called reactants. The reactants are written on the left hand side. The new substances produced as a result of chemical reaction are called products. The products are written on the right hand side. • Some of the symbols used in a chemical equation are : (a) Solids (s) (b) Liquids (l) (c) Gases (g) (d) Aqueous solutions (aq) (e) Gas released as a product (↑) (f) Precipitate formed in the reaction (↓) (g) Direction of reaction (→) (h) Used to separate multiple reactants or products (+) (i) Formula written above the arrow is used as a catalyst in the reaction (Pt) (J)Triangle indicates that the reaction is being heated (∆) (k)Replaces the yield sign for reversible reactions that reach equilibrium () • Steps to balance a chemical equation : (a) Write word equation. (b) Then write skeletal chemical equation. (c) Enclose the formula in the boxes. (d) List the number of atoms of different elements present in the unbalanced equation. (e) Start balancing with the compound that contains the maximum number of atoms. (f) Start balancing other atoms. (g) Check the correctness of the balanced equation. • Types of chemical equations : Exothermic Reactions CHEMICAL REACTION Endothermic Reactions [accompanied by evolution of heat] Example : CH4 + O2 o CO2 + H2O + Heat [accompanied by absorption of heat] Example : 2Pb (NO3)2 Heat 2PbO + 4NO2 + O2 REDOX REACTION Oxidation Reduction [Addition of O2 or removal of H2] [Addition of H2 or removal of O2] Example : Cu + O2 o 2CuO Example : 2Na + H2 o 2NaH

•CHARACTERISTICS OF A CHEMICAL EQUATION : (FLOW CHART) CHARACTERISTICS OF A CHEMICAL EQUATION Change Change Evolution Change in Formation in State in Colour of Gas Temperature of Precipitate Example : Example : Example : Example : Example : 1. Solid wax on 1. Iron (grey colour) 1. CaO+H2O o Ca(OH)2+Heat heating changes Changes to rust (brown 1. Zn + dil. H2SO4 o ZnSO4 + H2 n 1N.aANgON3 O+3 + NaCl o to gas. colour) on reaction with 2. CaCO3 o CaO + CO2 n AgCl (p) ppt. air or moisture. 2. Petrol (liquid) 2. CaCO3 + CO2 + H2O burns to form gas. 2. [PcboNloOu3rl+essK]I o P[bYI2el+lowK]NO3 o Ca(HCO3)2 p TYPES OF CHEMICAL REACTIONS Combination Decomposition Displacement Double Redox reaction reaction reaction reaction displacement reaction [Oxidation and reduction occurs [Single product is [Two or more products [More reactive metal [Exchange of ions simultaneous] formed from two or are formed by a single displaces a less between the reactive metal] reactants] more reactants] reactant] C(s) + O2(g) o CO2(g) Thermal decomposition Cation displacement Neutralisation Precipitation 2H2(g) + O2(g) o 2H2O(l) (takes place by heat) Example : (Cation) Electrolytic Decomposition Zn + CuSO4 o ZnSO4 + Cu (takes place by electricity) Anion displacement Photolysis Example : (Anion) (takes place by light) Cl2 + 2NaBr o 2NaCl + Br2 •EFFECTS OF OXIDATION IN EVERYDAY LIFE Corrosion EFFECT OF OXIDATION Rancidity IN EVERYDAY LIFE Conditions Example : Causes Example : for Corrosion • Rusting of iron. [oxidation of oil and fat Chips packet when kept • Air • Blackening of Silver articles. open becomes rancid present in food when cooked cooked oil kept for long time. • Moisture food is left for a long time]. Methods of Prevention Methods of Prevention • Oiling • Addition of antioxidants. • Painting • Packing in air tight container. • Galvanising • Refrigeration at low temperature. • Electroplating • Packing food in atmosphere of nitrogen.

CHAPTER-2 : ACIDS, BASES AND SALTS COMPOUNDS Acids Bases Salts Strong Acids Strong Bases Acidic Salts Those acids which dissociate Those bases which ionises completely to Salts of strong acids and weak base. completely into ions. furnish OH– ions are called strong bases. Ex. NH4Cl Ex. HCl, HNO3 etc. Ex.NaOH, KOH etc. Basic Salts Weak Acids Weak Bases Salts of strong base and weak acid. Those acids which dissociates Those bases which ionises only partially Ex. CH3COONa partially are called weak acids. are called weak bases. Ex. CH3COOH Ex. NH4OH Neutral Salts Salts of strong acids and strong ACIDS bases. Ex. NaCl Physical Properties Uses Chemical Properties • Sour taste. • HCl is used mainly in industries like cleaning • React with metals to give H2 gas. • Turns blue litmus red. boilers from inside, sink cleaning etc. Na + HCl o NaCl + H2 • Corrosive in nature. • Gives H+ ions in solution. • Nitric acid is used for making fertilizers, • React with metal carbonates to give salt • Conducts electricity. cleaning of gold. and CO2 gas. Na2CO3 + HCl o NaCl + H2O + CO2 • Sulphuric acid is used in cells, car, battery etc. • React with bases to give salt and water. BASES NaOH + HCl o NaCl + H2O • React with metal oxides to give salt and water. CuO + H2SO4 o CuSO4 + H2O Physical Properties Uses Chemical Properties • Bitter in taste. • NaOH is used to make soaps in paper industry • React with acids to form salt and water • Turns red litmus blue. and in textile industry. [Neutralisation] • Slippery to touch. NaOH + HCl o NaCl + H2O • Turns phenolphthalein solution pink. • Ca (OH)2 is used to remove acidity of soil. • Mg(OH)2 is used as an antacid. • Reacts with metals to from salt. 2NaOH + Zn o Na2ZnO2 + H2 • React with non-metal oxides to for salt and water. Ca(OH)2 + CO2 o CaCO3 + H2O

SALTS Sodium Hydroxide Baking soda Washing soda Calcium Plaster of paris caustic soda (NaOH) sodium bicarbonate sodium carbonate oxychloride Bleaching Calcium sulphate NaHCO3 Na2CO3.10H2O powder CaOCl2 hemihydrate Preparation Preparation Preparation Preparation Preparation NaCl + H2O + CO2 + NH3 2NaHCO3 Ca(OH)2 + Cl2 CaSO4∆·2H2O NaCl + HC2lO2 +oH2 2NaOH + CaSO4· 1/2 H2O + 3/2 H2O Uses NH4Cl + NaHCO3 Na2CO3 + H2O + CO2 CaOCl2 + H2O Uses • Metallurgy of bauxite • Used to join bones • Distillation of petrol Uses Uses Uses • 1In dentistry • Formation of soil • Food industry • Washing purposes • As a bleaching agent • Bakery • Paper and textile industry • Antacid Families of Salts Sodium Salts — NaCl, NaNO3, Na2SO4, Na2CO3, CH3COONa etc. Potassium Salts — KCl, KNO3, K2SO4, KBr, K2CO3 Ammonium Salts — NH4Cl, NH4NO3, NH4Br Magnesium Salts — MgCl2, MgSO4, MgCO3 Calcium Salts — CaCl2, Ca(COO)2, etc. Chloride Salts Formula Name of Salt Base Involved NaCl Sodium chloride NaOH KCl Potassium chloride KOH NH4Cl Ammonium chloride NH4OH BaCl2 Barium chloride Ba (OH)2 MgCl2 Magnesium chloride Mg(OH)2 Nitrate Salts Name of Salt Base Involved Sodium nitrate NaOH Formula Potassium nitrate KOH KCNNaa(NONO4O33)2 Calcium nitrate Ca(OH)2 Sulphate Salts Name of Salt Base Involved Sodium sulphate NaOH Formula Potassium sulphate KOH MKN2agS2SSOOO4 44 Magnesium sulphate Mg(OH)2 Carbonate Salts Name of Salt Base Involved Sodium Carbonate NaOH Formula Potassium Carbonate KOH KCN2aaCC2COOO333 Calcium Carbonate Ca(OH)2

CHAPTER-3 : METALS AND NON-METALS • Elements are classified into Metals, Non-metals and Metalloids Metals PHYSICAL Non-Metals PROPERTIES • Solid at room temperature. • Soft, solid or in gaseous state. • Hard and have high melting point and boiling point. • Neither malleable nor ductile. • Malleable and ductile. • Poor conductor of heat and electricity. • Good conductors of heat and electricity. • Low density. • High density. • Non-lustrous and non-sonorous. • Lustrous and sonorous. Exceptions Exceptions • Mercury is the only metal which is liquid at room temperature. • Bromine is the only non-metal which is liquid at room • Sodium and potassium are soft and have low melting point and boiling point. • Zinc is the only metal which is neither malleable nor ductile. temperature. • Mercury and Tungsten are poor conductors of heat and electricity. • Diamond is hardest substance. • Graphite is good conductor of heat and electricity. • Iodine and graphite are non-metals that exhibit metallic lustre. Metals CHEMICAL Non-Metals PROPERTIES With Oxygen With Oxygen M + O2 o M2O (basic) E + OO22 OC2O(2acidic) Metal (M)4Na + O2 o 2Na2O C + o Non-Metal (E)With Water o M + H2O o MOH Mg + H2O o Mg(OH)2 With Water With Acids E + H2O o No reaction M + Acid o Salt + H2 2Na + 2HCl o 2NaCl + H2 With Acids With Bases No reaction M + Base o Salt + H2 2Al + 2NaOH + 2H2O o 2NaAlO2 + 3H2 With Salt Solution Zn + 2NaOH o Na2ZnO2 + H2 2NaBr + Cl2 2NaCl + Br2 Note : (1) Copper oxide is black in colour. (2) Aluminium oxide is amphoteric oxide. (3) Sodium and potassium react violently with water. (4) Magnesium do not react with cold water. (5) Some metals like aluminium, iron and zinc do not react either with cold or hot water.

Formation IONIC COMPOUNDS Properties Formed by losing or Solid and hard gaining of electron or by Examples: High melting point an transfer of electrons CaNFa2C, lM, MgOgCelt2c. boiling point.Good between a metal a conductors of electricity Soluble in water. non-metal. EXTRACTION OF METALS Crushing Concentration Preliminary Reduction Purification of ore Treatment of ore Huge lumps of ore are Purification is done by broken into small pieces. Gravity Separation. Calcination Roasting distillation, liquidation or by electrolytic refining. Froth Floatation Ore is heated Ore is heated Process. in limited in excess supply of supply of Magnetic Separation. oxygen. oxygen. Leaching or chemical separation. REDUCTION • Metals at top of activity series. Na, K, Ca , Mg, Al • By electrolysis. • Metals at the middle of reactivity series. Zn, Fe, Pb • Metal in the lower region of reactivity series. Cu, Hg, Ag • Reduction using carbon or some reducing • Metals found at the bottom of activity series. Pt, Au agent. • Reduction by heating alone. • Found in native state.

CHAPTER-6 : LIFE PROCESSES • Living beings are complex organisations of molecules which perform various life processes like growth, respiration, digestion, reproduction, excretion etc., which makes them different from non-living. • The basic processes or functions performed by living organisms to keep them alive are called life processes. LIFE PROCESSES Nutrition Excretion Transportation Respiration • Nutrition is defined as the process of intake of nutrients and its utilisation by an organism in various biological activities. MODES OF NUTRITION Autotrophic Heterotrophic [Organisms prepare their [They depend on autotrophs for their food. Example : Animals, own food. Example : Plants, Algae]. Humans Beings]. Holozoic Parasitic Saprophytic [The process of intake of solid or liquid food by [The process of obtaining food [The process of obtaining food ingestion process, conversion of complex food directly from the body of host particles to simpler form by digestion, assimilation either by living on its surface or from the dead or decayed and finally removing the undigested food. Example : organisms. Example : Yeast, inside the body of host. Amoeba, Human Beings]. Example : Worms]. Mucor, Mushrooms. • In autotrophic mode of nutrition, organisms prepare their own food and they are called autotrophs. Organisms prepare food by the process of photosynthesis. • Photosynthesis is the process by which chlorophyll containing cells prepare glucose using carbon dioxide and water in presence of light energy and oxygen gas is released as a by product during this process. • 6CO2 + 12H2O Sunlight C6H12O6 + 6O2 + 6H2O [Equation for photosynthesis] Chlorophyll nCeocnedsistiaorny PHOTOSYNTHESIS Siptreoocfesthsis Carbon Dioxide [from air passes through Steps Chloroplasts [double stomata present on surface of leaves.] membrane bound organelle Water [absorbed by roots from soil] Light Reaction Dark Reaction which contains chlorophyll] Light Energy [trapped by chlorophyll] [occurs in grana] [occurs in stroma] Chlorophyll [present in chloroplasts] Absorption of light Reduction of carbon energy by chlorophyll dioxide to carbohydrates Photolysis of water to produce hydrogen and oxygen

BASED ON THEIR FOOD [EATING HABITS] Herbivores Carnivores Omnivores [They are plant eaters] [They eat other animals] [They eat both plants Example : Cow, goat, and animals] Example : Example : Lion, tiger sheep, etc. Man •STEPS OF NUTRITION IN HUMAN BEINGS STEPS OF NUTRITION IN HUMAN BEINGS Ingestion Digestion Absorption Assimilation Egestion [Process of taking [Conversion of large [Process of passing of [Absorbed food taken [Removal of undigested of food by the body.] insoluble molecules into digested food throught by body cells for its food from the body.] In human beings we smaller and simpler the intestinal wall into growth, repair and The undigested food from take the food through forms.] bloodstream.] reproduction etc.] small intestine passes our mouth. The absorbed food into large intestine water Food is crushed with the The digested food is passes into blood- and salts are absorbed help of teeth and enzyme absorbed by intestinal stream, through blood and undigested solid ptyalin present in saliva, walls through finger like it reaches the cells and are removed in the form acts upon starch present projections called villi. is utilised by cells to of faeces. in food to convert into obtain energy for simple sugar. growth, repair etc. The food in form of bolus is transferred to stomach by peristaltic movement through oesophagus. In stomach food is digested by action of gastric juice secreted by gastric glands. Mainly enzyme pepsin acts upon proteins to convert into peptones and proteases. Then food passes to small intestine where remaining food is digested by actions of pancreatic juice and intestinal juice. Fats are converted into small globules by action of bile juice secreted from liver by a process called emulsification. •ORGANS OF THE DIGESTIVE SYSTEM

ALIMENTARY CANAL Mouth Oral Cavity Oesophagus Stomach Small Large or Food Pipe Intestine Intestine Salivary glands Teeth help in Food in form of Gastric glands [Secrete salivary mastication and bolus passes from secrete gastric Receives pancreatic No digestion only amylase or ptyalin] chewing of food mouth to stomach juice juice from pancreas absorption of Ptyalin acts upon Tongue helps in through oesophagus Gastric juice excess water, starch to convert mixing of food by peristalsis contains pepsin Amylase Lipase Trypsin some salts and to maltose with saliva which converts finally the proteins to Starch Lipids Peptones, undigested peptones to simple to fatty proteins residue is left sugars acids to peptides behind and glycerol Intestinal juice Secretes enzymes which completes the conversion of proteins to amino acids, carbohydrates to glucose, fats to fatty acids and glycerol Bile from liver Emulsify large fat globules to smaller ones •NUTRITION IN AMOEBA •RESPIRATION • Respiration is a biological process by which glucose is oxidized to release energy in the form of ATP which is the energy currency of the cell. • C6H12O6 + 6O2 Sunlight 6CO2 + 6H2O + Energy [Equation for respiration] • During aerobic respiration, 38 molecules of ATP are released whereas during anaerobic respiration only 2 molecules of ATP are released. • Tobacco is a plant and its leaves are smoked, chewed, or sniffed for a variety of effects. Tobacco contains nicotine, an addictive substance. Smoked tobacco products include cigarettes, cigars, bidis, and kreteks. • Smoking can destroy the cilia or tiny hairs in the airway that keep dirt and mucus out of lungs.

RESPIRATION Cellular or Tissue Respiration Breathing In aquatic organisms like fishes In amoeba exchange of a gases occurs In plants exchange of gases occurs In humans respiratory exchange of gasses occurs through try simple diffusion through its body through stomata organs are lungs gills surface CELLULAR RESPIRATION Aerobic Anaerobic [In presence of [In absence of oxygen] oxygen] Glycolysis [Glucose a 6 Krebs’ Cycle In presence Glucose Pyurvic acid carbon compound breaks of excess supply of oxygen into a 3 carbon compound pyurvic acid completely Lactic acid [In muscles Ethanol and carbon pyurvic acid in cytoplasm] breaks down into carbon dioxide of human beings during dioxide [In yeast and water in mitochondria] strenous physical exercise] during fermentation] •BREATHING PROCESS IN HUMAN BEINGS BREATHING IN HUMAN BEINGS Air passes through During inhalation Air from nasal Air from traches During exhalation, nostrils where the ribs moves outwards, cavity moves to goes to bronchi and ribs moves inwards inhaled air is diaphragm moves pharynx, larynx then to smaller and diaphragm moves filtered by hairs and downwards so and then into bronchioles and into its original mucus membrane chest cavity trachea [wind pipe] finally to alveoli position, thus thoracic lining nasal cavity increases and air where exchanges cabity decreases and is forced inside of gases occurs air is expelled out from lungs through nostrils •TRANSPORTATION • The essential substances like food, water, oxygen etc., need to be carried from one part of the body to another which is done by transport system. • Arteries carry oxygenated blood except pulmonary artery. • Veins carry deoxygenated blood except pulmonary vein. • Capillaries are thin walled blood vessels where exchange of gases and materials like food occurs. • Valves allow the blood to flow in one direction i.e., they prevent back flow of the blood. • When blood flows from atria to ventricles atria contracts and ventricle relaxes, this is called ventricular diastole. • When blood flows from ventricles to blood vessels, ventricles contract and atrium relaxes, this is called ventricular diastole. • The force exerted by blood on the walls of blood vessels is called blood pressure. • The normal blood pressure of human beings is 120/80 mm of Hg. • As blood flows in our heart twice so circulation in human beings is called double circulation.

TRANSPORTATION In Human In plants Beings Lymphatic system Blood vascular system Blood Xylem carries Water and minerals water and salts are mainly transported Lymph It contains Plasma Blood cells from roots to through tracheids or mainly [Transpor t RBCs[carry oxygen] leaves and other vessels lymphocytes food, gases, WBCs[Immunity] parts of plant Transportation of water which fight nitrogenous Platelets[Blood clotting] Phloem conducts and minerals has against infection wastes, etc.] food from leaves three process Blood vessels to other parts Lymph vessels Ar teries of plant Veins Lymph nodes Capillaries Food is mainly translocated by Lymph capillaries Heart [Contains two sieve tubes of atria and two ventricles, phloem in dilute main pump organ] aqueous solution form Absorption of Ascent of sap Loss of excess water and minerals by root pressure water in form from soil to root or transpiration of vapours by hairs by osmosis pull process of and active transport transpiration process respectively MECHANISM OF BLOOD CIRCULATION De-oxygenated blood form different parts of the body through venacava enters into right atrium of heart Then it moves to right ventricle through tricuspid valve Blood from right ventricle goes to lungs by pulmonary artery for purification Oxygenated blood from lungs comes to left atrium by pulmonary veins Then blood moves to left ventricle through bicuspid valve Finally by aorta oxygenated blood is transported all over body from left ventricle

•DOUBLE CIRCULATION •EXCRETION EXCRETION Excretion in human beings Excretion in plants Excretory organs Steps involved in Oxygen gas produced during process of excretion photosynthesis is removed A pair of kidneys through stomata [Nephrons are structural Ultrafiltration Carbon dioxide gas produced and functional units] [Blood is filtered through during respiration is expelled A pair of ureters glomerulus and collects in out through stomata [Urine passes through Bowman’s capsule as it flows Some released directly to soil, ureter to bladder] with high pressure known as waste stored in leaves fall off Urinary bladder glomerular filtrate] Excess water removed by [Stores urine] transpiration Urethra Selective reabsorption Some in form of resins, gums [Removes urine to outside [Glomerular filtrate contains many Some waste products stored when bladder is full] useful substances like glucose, water, in vacuoles salts which are selectively reabsorbed in different parts of nephron] Tubular secretion [Some harmful substances are secreted from tubules of nephron to the formed urine] • The process of removal of mainly nitrogenous waste substances from our body is called excretion. • In case of kidney failure due to infections or injury or other factors artificial kidney is used. • Artificial kidney is a device that removes nitrogenous wastes from our body by dialysis. • Organ donation is the donation of biological tissue or an organ of the human body, from a living or dead person to a living recipient in need of a transplantation. Organ transplantation is the only option to save lives in patients affected by terminal organ failures and improve their quality of life.

CHAPTER-10 : LIGHT : REFLECTION AND REFRACTION Reflection LIGHT Refraction • The return of light into the same medium after Light is a form of energy that striking a surface is called reflection. causes the sensation of vision. • The change in direction of light when it passes from one medium to another obliquely, is called refraction of light. • The refraction of light is due to the change in the speed of light on going from one medium to another. Laws of Laws of Reflection Refraction • The incident ray, the reflected ray and the normal • The incident ray, the refracted ray and the normal at the all lie in the same plane. point of incidence, all lie in the same plane. • The angle of reflection is always equal to the angle of incidence. • The ratio of sine of angle of incidence to the sine of angle of refraction is constant for a given pair of media. Important Important Points Points • When the reflecting surface is smooth, the parallel rays of light falling • A medium in which the speed of light is more is known as on it are reflected in one direction. This is called regular reflection. optically rarer medium. • When the reflecting surface is rough, the parallel rays of light falling on • A medium in which the speed of light is less, is known as it are reflected in different directions. This is called irregular reflection. optically denser medium. • When a ray of light goes from a rarer medium to a denser medium, it bends towards the normal and when it goes from denser to rarer medium, it bends away from the normal. • The refractive index of medium 2 with respect to medium 1 is equal to the ratio of speed of light in medium 1 to the speed of light in medium 2. Plane Mirror TYPES OF MIRRORS Spherical Mirror • A plane mirror is a thin, flat and smooth sheet of glass having a • A spherical mirror is that mirror whose reflecting surface is shining coating of silver metal on one side. the part of a hollow sphere of glass. • It is represented by a straight line having a number of short, Concave Mirror Convex Mirror oblique lines on one side. • A sperical mirror in which • A sperical mirror in which Characteristics the reflection of light takes the reflection of light takes place at the concave surface place at the convex surface • The image formed is virtual and erect. (or bent-in surface). (or bulging-out surface). • The image is of the same size as the object. • The image is at the same distance behind the mirror as the object is in front of the mirror. • The image formed is latterally inverted. Uses • These are used to see ourselves, in making periscopes etc. Important Points • Anything which gives out light rays is called an object. • Image is an optical appearance produced when light rays coming from an object are reflected from a mirror. • The image which can be obtained on a screen is called a real image. • The image which cannot be obtained on a screen is called a virtual image.

CONCAVE MIRROR Rules for image formation Uses Image formation by a concave mirror for different • Rays, parallel to the principal axis, These are used as positions of the object shaving mirrors, get reflected back through focus. reflectors in torches, Position of Position of Size of the Nature of • Rays, passing through the focus, doctor’s head-mirrors the object the image image the Image will emerge parallel to the principal etc. At infinity At the focus F Highly diminished, Real and axis after reflection. point-sized inver ted • Rays from the centre of curvature get reflected back along its own path. Beyond C Between F and C Diminished Real and inverted • A ray of light incident obliquely at pole gets reflected at the same angle on the At C At C Same size Real and other side of principal axis into the same Enlarged inver ted medium. Between F Beyond C Highly enlarged and C Enlarged Real and At F At infinity inver ted Between P Behind the Real and and F mirror inver ted Vir tual and erect CONVEX MIRROR Rules for image formation Uses Image formation by a convex mirror for different • Rays parallel to principal axis, get reflected These are used as positions of the object rear-view mirrors in and appear to come from the principal focus. vehicles and shop Position of Position of Size of the Nature of security mirrors etc. the object the image image the Image • Rays going towards the principal focus, will emerge parallel to the principal axis after reflection. At infinity At the focus Highly Vir tual F, behind the diminished, and erect • Rays from the centre of curvature get reflected point-sized back along its own path. mirror • A ray of light incident obliquely at pole gets Between Between P Diminished Vir tual reflected at the same angle on the other side of infinity and and F, behind and erect principal axis into the same medium. the pole P of the mirror the mirror New Cartesian Sign Convention for Spherical mirrors Convex Spherical Lenses Concave Lens A lens is a piece of Lens transparent glass bound • A is thick at the centre but thinner at the edges. by two spherical • A is thin in the middle but thicker at the edges. • It converges light rays. • It diverges light rays. surfaces. Convex lens Concave lens

CONVEX LENS Image formation rules Uses Image formation by a convex mirror for different • Rays parallel to principal axis, will pass These are used in positions of the object making microscopes, through second principal focus after telescopes, slide Position of Position of Relative size of Nature of refraction. projectors, magnifying the object the image the image the Image • Rays passing through the focus will emerge parallel to the principal axis after glass etc. At infinity At the focus F2 Highly diminished, Real and inverted refraction. point-sized • Rays passing through the optical centre, will emerge without any deviation after Beyond 2F1 Between F2 and 2F2 Diminished Real and inverted refraction through the lens. Real and inverted At 2F1 At 2F2 Same size Real and inverted Between F1 Beyond 2F2 Enlarged Real and inverted and 2F1 At focus F1 At infinity Infinitely large or Highly enlarged Between focus On the same Enlarged Virtual and erect F1 and optical side of the lens centre O as the object CONCAVE LENS Image formation rules Uses Image formation by a concave mirror for different • Rays parallel to principal axis appear to These lenses are used positions of the object in spectacles to correct diverge from the principal focus, which is the defect of vision, Position of Position of Size of the Nature of located on the same side of the incident ray. wide-angle spy hole in the object the image image the Image • Ray going towards the principal focus, will emerge parallel to the principal axis after refraction. doors etc. At infinity At the focus F1 Highly diminished, Virtual and erect • Rays passing through the optical centre will point-sized emerge without any deviation after refraction through the lens. Between Between focus Diminished Virtual and erect infinity and F1 and optical Optical centre centre O O of lens New Cartesian Sign Convention for Spherical Lenses

CHAPTER-11 : THE HUMAN EYE AND COLORFUL WORLD Only Natural Phenomena is examinable for Term I examination. The Human Eye The human eye uses light and enables us to see the colourful world, beautiful nature and natural phenomenon. Iris Pupil Ciliary Muscles Cornea • A coloured diaphragm between • A hole in the middle of the iris. • It changes the thickness of the cornea and the lens. • It appears black as no light eyelens and thus, the focal • The outermost part of the eye. length of the lens by changing • It allows the light to enter the • It controls the size of the pupil. gets reflected from it. its shape. • It controls the amount of eye. Eye Lens light entering the eye. Retina MAIN PARTS OF THE • A fibrous, jelly like HUMAN EYE transparent convex lens. • A delicate membrane containing number of light sensitive cells. • It forms a real image of the objects on the retina. • It acts as a screen on which the image is formed. Rods Cones Optic Nerve Power of Accommodation The rod-shaped The cone-shaped • The ability of the eye to focus on the distant objects as cells present in the cells present in the retina • It transports the electrical signals retina of an eye which of an eye which are from retina to the brain. well as on the nearby objects on the retina by changing are sensitive to sensitive to bright the focal length of its lens is called the power of accommodation of eye. dim light. light. • The minimum distance, at which Objects can be seen distinctly without strain, is called the least distance of distinct vision or the near point of the eye. It is about 25 cm for a normal eye. • The farthest point upto which the eye can see objects clearly is called the far point of the eye. It is infinity for a normal eye.

DEFECTS OF VISION Myopia Hypermetropia Presbyopia Cataract • Defect of vision due to which a person • Defect of vision due to which a • Defect of vision due to which an old • The cataract defect is developed can see nearby objects clearly but person can see distant objects person cannot see the nearby objects when the eye lens of a person cannot see distant object distinctly. clearly but cannot see nearby objects clearly due to loss of power of becomes cloudy due to the distinctly. accommodation of the eye. formation of a membrane over it. • It is caused by the following two reasons: • It is caused by the following two • The causes of presbyopia are : • The defect of the cataract leads to: » Decrease in the focal length of the reasons : » Gradual weakening of the ciliary » Decrease in the vision of the eye-lens. » Increase in the focal length of the muscles. eye gradually. » The size of the eyeball becomes eye lens. » Diminishing flexibility of the eye » Total loss of vision of the eye. too long. » The size of the eyeball becomes lens. • It can be rectified after getting • It is corrected by using spectacles too short. • It can be corrected by using bifocal surgery done on the eye in which containing concave lenses. • It is corrected by using spectacles lens. the cloudy layer is removed and containing convex lenses. eye lens is replaced with new artificial lens. (a) Far point of a myopic eye (a) Near point of a Hypermetropic eye (b) Myopic eye (b) Hypermetropic eye (c) Correction for myopic eye (c) Correction for Hypermetropic eye NATURAL PHENOMENA Refraction of light Dispersion Atmospheric Scattering through a glass prism of Light Refraction of Light • A homogeneous, transparent refracting • The splitting of white light into its • The refraction of light caused by • When sunlight enters the earth’s medium bound by atleast two non-parallel component colours on passing the earth’s atmosphere. atmosphere, the atoms and surfaces inclined at some angle is called through a transparent medium molecules of different gases in a prism. like a glass prism. • Some of the phenomena which the atmosphere absorb this light occur due to atmospheric and re-emit it in all directions. Fig. : Refraction of light through a • The white light disperses into its refraction are: triangular glass prism seven colour components in the • The scattering of light by particles order VIBGYOR i.e., Violet, Indigo, » Twinkling of stars. in its path is called Tyndall effect. PE - Incident ray Blue, Green, Yellow, Orange, Red. » The stars seem higher than they EF - Refracted ray • Some phenomena which occur FS - Emergent ray • The red colour has the maximum actually are. due to scattering of light are : ∠A - Angle of the prism speed in the prism, so it deviates » Advance sunrise and delayed ∠i - Angle of incidence the least while the violet colour » The colour of the sky is blue. ∠r - Angle of refraction has the minimum speed, so sunset. » The sun appears red at sunrise ∠e - Angle of emergence it deviates the most. ∠D - Angle of deviation and sunset.

218 CBSE Final Revision of Term-I (Class X) Science Multiple Choice Questions 1. In the given figure, the position of the object is A (symbols have their usual meanings). DB Object C O 2h (a) Beyond 2F Image For which labelled part(s) A, B, C and D, the below (c) Between O and F given information is correct? Ans. (b) Between F and 2F (b) Between F and 2F (d) At F (a) A – Trachea – Rings of cartilage are present which Object ensure that the air passage does not collapse. 2F F F 2F (b) B – Nostril – Filters the air (c) C – Bronchiole – Flattens during breathe in the air Image (d) D – Alveoli – Provide surface for exchange of gases Ans. (a) A – Trachea – Rings of cartilage are present which Explanation: ensure that the air passage does not collapse. In case of convex lens, when object is placed between (d) D – Alveoli – Provide surface for exchange of gases Explanation: Here, A is trachea, B is lung, C is rib cage and D is alveolus. the F and 2F, the image formed is enlarged, real and 4. If in a Cartesian plane, a convex lens is placed at the inverted. § f · origin and a light source is placed at a point ©¨  3 ,0 ¹¸ 2. Consider the given chemical reaction where f is the focal length of the lens, then MnO2 + 4HCl MnCl2 + 2H2O + Cl2 (a) Virtual image of magnification 3 will be formed at 2 The substances getting reduced and oxidised respectively in the above chemical reaction are (a) Cl2 and MnO2 (b) MnO2 and HCl §  3f , 0 · ¨© 2 ¸¹ (c) MnO2 and Cl2 (d) HCl and MnO2 (b) Virtual image of magnification 4 will be formed at Ans. (b) MnO2 and HCl 3 Explanation: § 3f , 0 · ©¨ 2 ¹¸ MnO2 + 4HCl ® MnCl2 + 2H2O + Cl2 Removal of oxygen and addition of hydrogen is called (c) Virtual image of magnification 3 will be formed at reduction substances getting reduced act as oxidising 4 agent and vice-versa. § 3f · In above reaction since Mn loses oxygen, hence MnO2 ©¨ 2 , 0 ¸¹ is getting reduced. On the other hand Hydrogen gains (d) Virtual image of magnification 3 will be formed at oxygen to form water hence HCl is oxidised. 2 3. Consider the diagram of human respiratory system § 3f , 0 · given below. ¨© 2 ¹¸

Science 219 Ans. (a) Virtual image of magnification 3 will be formed at ∠i = 90º – 30º = 60º 2 ∠i = ∠r = 60º ∠i + ∠r = 60º + 60º = 120º §  3f , 0 · ¨© 2 ¸¹ 7. The dispersion of white light in a medium implies that Explanation: (a) Light of different wavelengths have different speeds. u  f ,v ? 3 (b) The red light bends the least while the violet the (0, 0) most. 1 = 1−1 §  f ,0 · (c) The refractive indices are different for different f vu ¨© 3 ¸¹ wavelength. (d) The violet light bends the least while the red the 1 = 1+ 3 most. f v f Ans. (a) Light of different wavelengths have different ⇒ 1= −2 speeds. v f ⇒ v = − f 2 (b) The red light bends the least while the violet the m = v most u (c) The refractive indices are different for different f wavelength 2 =3 Explanation: f 2 3 Virtual image of magnification 3 will be formed at 2 § 3f · Red ¨©  2 , 0 ¹¸ White light Orange Yellow When object is placed between focus and optical Green Blue centre, then image formed will be virtual, erect enlarged Indigo and on the same side of the object. Violet 5. Which of the following substances cannot be used to neutralise an acid extract? The refractive indices are different for different wavelength and speed of light is depended on refractive (a) Suspension of milk of (b) Baking powder solution index i.e., light of different wavelengths have different Magnesia speeds in a medium that is why violet colour bends the most and red colour least. (c) Dock leaf extract (d) Nettle leaf extract Ans. (d) Nettle leaf extract 8. Consider the following flow chart and the statements Explanation: given below: Nettle leaf extract contains methanoic acid hence X(g) cannot be used to neutralise an acid exact as acids are (Cathode) neutralised by base and vice versa. This is known as neutralisation reaction. Electrolysis Z(aq) HCl (aq)o W  H2O Brine 6. A ray of light incident on a plane mirror at an angle of Y(g) 30º with the mirror. The angle between incident ray (Anode) and reflected ray is: Now, choose the correct statement. 30º (a) W is an acidic compound (b) X is chlorine gas Plane mirror (c) Z is basic in nature (d) pH of Z < 7 (a) 60º (b) 120º (c) 90º (d) 150º Ans. (b) 120º Ans. (c) Z is basic in nature Explanation: Explanation: ir X, Y, Z and W are H2, Cl2, NaOH and NaCl respectively. 30º Electrolysis of brine is used for manufacture of chlorine gas. Useful chemicals obtained are sodium hydroxide (NaOH) and hydrogen (H2). The gas is evolved at cathode while Cl2 collected at anode during the process. NaOH formed is basic in natura as its pH > 7.

220 CBSE Final Revision of Term-I (Class X) 9. Select the correct one from the following regarding When water of crystallination is removed from a haemodialysis. compound it yields anhydrous form of compound along with water. Since in above question anhydrous X is (a) (Osmotic pressure)Blood earlier green in colour which is characteristic colour of = (Osmotic pressure)Dialysing Fluid FeSO4. 7H2O. (b) (Osmotic pressure)Dialysing Fluid > (Osmotic pressure)Blood Green crystals of (c) (Osmotic pressure)Dialysing Fluid FeSO4. 7H2O < (Osmotic pressure)Blood (d) (Osmotic pressure)Blood Anhydrous FeSO4 H2O > (Osmotic pressure)Dialysing Fluid Δ Ans. (a) (Osmotic pressure)Blood = (Osmotic pressure)Dialysing Fluid Fe2O3 SO2 SO3 Explanation: 2FeSO4 Δ During haemodialysis osmotic pressure of blood and Fe2O3 + SO2 + SO3 that of dialysing fluid are equal. Osmotic pressure is (S) (G1) (G2) about 28mm of Hg of fluid which is similar to oncotic pressure of plasma which is about 25 to 26 mm of Hg. 12. Consider the following elements and their electronic configuration 10. For a real object, placed in front of a spherical mirror, an image of magnitude of magnification 2 is formed. M = 2, 8, 8, 2 The nature of the mirror and the position of the object respectively are (symbols have their usual meanings) N = 2, 6 (a) Converging, between F and C X = 2, 8, 7 (b) Converging, beyond C Y = 2, 8, 5 (c) Converging, between F and P The non-metallic element(s) is/are : (d) Diverging, between F and C (a) M (b) N Ans. (a) C onverging, between F and C (c) X (d) Y Explanation: Ans. (b) N, and (d) Y The spherical mirror cannot be convex because it does Explanation: not form real image (that can be formed on a screen). So, the mirror has to be concave. In case of concave M, N, X and Y are calcium, oxygen, chlorine and mirror, the real image is formed if the object distance phosphorus respectively. is greater than focal length. For enlarged real image the object should be placed between the center and focus 13. The ___(i)___ which is not used immediately is stored of the mirror. in the form of ___(ii)___, which serve(s) as the internal energy reserve to be used as and when required by the 11. Consider the following flow chart, plant. Green coloured Here, (i) and (ii) respectively are crystals of X (a) Carbon dioxide and water Heat (b) Glucose and starch (c) Starch and glucose Anhydrous X H2O (d) Carbon dioxide and glucose Heat Ans. (b) Glucose and starch Explanation: Solid (S) Gas (G1) Gas (G2) During photosynthesis, glucose is synthesized by plants which gets stored in the form of starch, which can be S, G1 and G2 respectively can be broken down back into glucose via cellular respiration in order to supply ATP. (a) Pb(NO3)2, N2O, O2 (b) Pb(NO3), NO2, O2 (c) Fe2O3, SO2, SO3 (d) FeSO4, O2, SO3 14. Match the columns: Ans. (c) Fe2O3, SO2, SO3 Column I Column II Explanation: (A) Aqueous solution (P) Turns phenolphthalein X, S, G1 and G2 are FeSO4. 7H2O, Fe2O3, SO2 and SO3 of CO2 pink respectively. (B) 10 mL water + 20 mL (Q) pH is more than 7 milk of Magnesia

Science 221 (C) Lime water (R) Turns red litmus blue Ans. (d) BaCl2(aq) + Na2SO4(aq) BaSO4(s) + 2NaCl(aq) (D) Aqueous solution (S) Turns blue litmus red of sodium oxide Explanation: The number of particles on both the sides of the equation are equal. Ans. A(S), B(P, Q, R), C(P, Q, R), D(P, Q, R) 18. Three beakers labelled as A, B and C each containing Explanation: 25 mL of water were taken. A small amount of NaOH, (1) Aqueous solution of CO2 i.e., H2CO3 (Carbonic acid), anhydrous CuSO4 and NaCl were added to the beakers is acidic in nature therefore it turns blue litmus red. A, B and C respectively. It was observed that there (2) Solution of milk Magnesia, sodium oxide and lime was an increase in the temperature of the solutions water are basic in nature therefore their pH is more than 7 and they turn phenolphthalein pink and red contained in beakers A and B, whereas in case of litmus blue. beaker C, the temperature of the solution falls. Which 1 5. Which among the following statements(s) is (are) true? Exposure of silver chloride to sunlight for a long one of the following statements(s) is (are) correct? duration turns grey due to  [NCERT Exemplar] [NCERT Exemplar] (i) the formation of silver by decomposition of silver chloride (i) In beakers A and B, exothermic process has (ii) sublimation of silver chloride occurred. (iii) decomposition of chlorine gas from silver chloride (iv) oxidation of silver chloride (ii) In beakers A and B, endothermic process has occurred. (iii) In beaker C exothermic process has occurred. (iv) In beaker C endothermic process has occurred. (a) (i) only (b) (ii) only (a) (i) only (b) (i) and (iii) (c) (i) and (iv) (d) (ii) and (iii) (c) (ii) and (iii) (d) (iv) only Ans. (c) (i) and (iv) Ans. (a) (i) only Explanation: Explanation: During exothermic reaction temperature of reaction mixture increases and energy is released whereas in When silver chloride is exposed to light it decomposes endothermic reaction temperature decreases and energy to form silver metal and chlorine gas absorbed. Since temperature in A and B increases it is exothermic process while in C temperature decreases 2AgCl D 2Ag + Cl2 so is endothermic process. White colour of silver chloride changes to grey due to 19. A dilute ferrous sulphate solution was gradually the formation of silver metal. 16. The correct sequence of anaerobic reactions in yeast is added to the beaker containing acidified potassium [NCERT Exemplar] permanganate solution. The light purple colour of (a) Glucose Cytoplasmo Pyruvate Mitochondriao the solution fades and finally disappears. Which Ethanol + Carbon dioxide of the following is the correct explanation for the (b) Glucose Cytoplasmo Pyruvate Cytoplasmo Lactic acid observation?  [NCERT Exemplar] (c) Glucose Cytoplasmo Pyruvate Mitochondriao (a) KMnO4 is an oxidising agent, it oxidises FeSO4 Lactic acid (b) FeSO4 acts as an oxidising agent and oxidises (d) Glucose Cytoplasmo Pyruvate Cytoplasmo KMnO4 Ethanol + Carbon dioxide (c) The colour disappears due to dilution; no reaction is Ans. (d) Glucose Cytoplasmo Pyruvate Cytoplasmo involved Ethanol + Carbon dioxide (d) KMnO4 is an unstable compound and decomposes in presence of FeSO4 to a colourless compound. Ans. (a) KMnO4 is an oxidising agent, it oxidises FeSO4 Explanation: 17. Identify the chemical equation which represents a FeSO4 + KMnO4 + H2SO4 Fe2(SO4)3 + MnSO4 complete balanced equation for the reaction of barium Purple colour chloride with sodium sulphate to produce barium sulphate and sodium chloride. + K2SO4 + H2O KMnO4 is oxidizing agent in above reaction as it oxidizes FeSO4(Fe2+) (+2 oxidation state) to Fe2(SO4)3(Fe+3) (a) BaCl2(aq) + Na2SO4(aq) BaSO4(s) + NaCl(aq) (+3 oxidation state). (b) BaCl2(aq) + Na2SO4(aq) 2BaSO4(s) + 2NaCl(aq) 20. Which of the following is (are) an endothermic (c) 2BaCl2(aq) + Na2SO4(aq) processes?  [NCERT Exemplar] 2BaSO4(s) + NaCl(aq) (i) Dilution of sulphuric acid. (d) BaCl2(aq) + Na2SO4(aq) BaSO4(s) + 2NaCl(aq) (ii) Sublimation of dry ice. (iii) Condensation of water vapours. (iv) Evaporation of water.

222 CBSE Final Revision of Term-I (Class X) (a) (i) and (iii) (b) (ii) only Explanation: (c) (iii) and (iv) (d) (ii) and (iv) Ans. (d) (ii) and (iv) 2Kl + Pb(NO3)3 → PbI2 + 2KNO3 Explanation: Potassium iodide and lead nitrate dissociates in aqueous Endothermic process are those in which energy is state to form ions. Lead (Pb2+) and iodide (I–) forms absorbed by substances and temperature of reaction precipitate of lead iodide (Pb2I). If lead sulphate is used mixture falls or decrease. Since in sublimation of dry no precipitate of PbI2 is formed, whereas lead acetate Cl and evaporation of water, in both the reactions dissociates in aqueous state to give Pb2+ and CH3COO– energy is absorbed for change in state, hence both are Hence potassium iodide combines with lead acetate to endothermic processes. form lead iodide and potassium acetate. 21. Which of the following are combination reactions? 2KI + Pb(CH3COO)2 PbI2 + 2CH3COOK [NCERT Exemplar] 24. Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by liberation (i) 2KClO3 2KCl + 3O2 of heat. This process is called slaking of lime. Calcium (ii) MgO + H2O Mg(OH)2 hydroxide dissolves in water to form its solution (iii) 4Al + 3O2 called lime water. Which among the following is/ (are) (iv) Zn + FeSO4 2Al2O3 true about slaking of lime and the solutiohn formed? ZnSO4 + Fe  [NCERT Exemplar] (a) (i) and (iii) (b) (iii) and (iv) (i) It is an endothermic reaction (c) (ii) and (iv) (d) (ii) and (iii) Ans. (d) (ii) and (iii) (ii) It is an exothermic reaction Explanation: (iii) The pH of the resulting solution will be more than Combination reactions are reactions in which two or more seven than two substances combine to give a new products. In above questions as (i) a single compound gives two (iv) T he pH of the resulting solution will be less than compound it is a decomposition reaction. In (ii) and (iv) two seven compounds combine to give an entirely new product hence these are examples of combination reaction. (a) (i) and (ii) (b) (ii) and (iii) (c) (i) and (iv) (d) (iii) and (iv) Ans. (b) (ii) and (iii) Explanation: 22. What happens when carbon dioxide is passed through Quick lime (CaO) combines with water to form calcium lime water? hydroxide [Ca(OH)2]. It is an exothermic reaction as (a) Lime water turns milky because of formation of heat is produced in reaction. calcium carbonate CaO + H2O → Ca(OH)2 + Heat (b) Lime water turns milky because of formation of water On adding excess Ca(OH)2 in water saturated solution of Ca(OH)2 is formed called as lime water which is basic (c) Lime water turns red because of formation of in nature and hence has pH above 7. permanganate 25. The following reaction is used for preparation of (d) Lime water turns red because of formation of copper oxygen gas in the laboratory: sulphate. 2KClO3(s) Heat o 2KCl(s) + 3O2(g) Ans. (a) Lime water turns milky because of formation of calcium carbonate Catalyst Explanation: Which of the following statements is correct about the CaO + CO2 → CaCO3 reaction?  [NCERT Exemplar] CO2 turns milky due to formation of CaCO3. (a) It is a decomposition reaction and endothermic in 23. In the double displacement reaction between aqueous nature potassium iodide and aqueous lead nitrate, a yellow precipitate of lead iodide is formed. While performing (b) It is a combination reaction. the activity if lead nitrate is not available, which of the following can be used in place of lead nitrate? (c) It is a combination reaction and is accompanied by release of heat. [NCERT Exemplar] (d) It is a photo chemical decomposition reaction and (a) Lead sulphate (insoluble) exothermic in nature. (b) Lead acetate (c) Ammonium nitrate Ans. (a) It is a decomposition reaction and endothermic in (d) Potassium sulphate nature Ans. (b) Lead acetate Explanation: Since a single compound breaks into its constituents hence it is an example of decomposition reaction and as heat is released in reaction so is also endothermic in nature.

Science 223 26. The following reaction is an example of a Explanation: 4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g) Since the number of the atoms on both sides of the reaction are equal thus it is a balanced chemical reaction. (i) displacement reaction (ii) combination reaction (iii) redox reaction (iv) neutralisation reaction 29. A student learns that some products are formed as a result of combining two compounds while some [NCERT Exemplar] products are formed as a result of dissociation of two compounds. Two reactions are: (a) (i) and (iv) (b) (ii) and (iii) Reaction P – CaO + SO3 → CaSO4 (c) (i) and (iii) (d) (iii) and (iv) Reaction Q – ZnCO3 → ZnO + CO2 Which reaction is an example of a combination Ans. (c) (i) and (iii) reaction and a decomposition reaction? Explanation: (a) Both the reactions are example of a decomposition A reaction in which reduction and oxidation occurs reaction simultaneously is called redox reaction. (b) P is example of a decomposition reaction while 4NH3 + SO2 → 4NO + 6H2O reaction Q is an example of a combination reaction. Here nitrogen undergoes oxidation at same time (c) Reaction P is an example of a combination reaction oxygen is reduced so it is a redox reaction. Since while reaction Q is an example of a decomposition hydrogen is replaced by oxygen so it is also an example reaction. of displacement reaction. (d) B oth the reactions are examples of combination 27. Which of the following are exothermic processes? reaction. (i) Reaction of water with quick lime (ii) Dilution of an acid Ans. (c) Reaction P is an example of a combination reaction (iii) Evaporation of water while reaction Q is an example of a decomposition (iv) Sublimation of camphor (crystals) reaction. (a) (i) and (ii) (b) (ii) and (iii) Explanation: (c) (i) and (iv) (d) (iii) and (iv) As in P two compounds combine to form a new product where as in reaction Q a single compound is broken into Ans. (a) (i) and (ii) its constituents reactants. Explanation: Since heat is released and temperature of reaction 30. A researcher adds barium hydroxide to hydrochloric mixture increases in (i) and (ii) reaction so both are acid to form a white coloured barium chloride. Which examples of exothermic reaction. option gives the balanced chemical equation of the reaction? 28. A student writes a balanced chemical equation as (a) HCl + 2Ba(OH) → 2BaCl2 + 2H2O + O2 Pb(s) + CuCl2(aq) → PbCl2(aq) + Cu(s) (b) 2HCl + Ba(OH)2 → BaCl2 + 2H2O Which option gives the number of atoms on the LHS (c) 2HCl + 2Ba(OH)2 → BaH2 + 2HCl + O2 (d) 2HCl + Ba(OH)2 → BaH2 + 2HCl + O2 and RHS of the chemical equation? Ans. (b) 2HCl + Ba(OH)2 → BaCl2 + 2H2O Explanation: Elements Number of Atoms Number of Atoms in Reactants (LHS) in Products (RHS) Since in the above reaction the number of atoms are equal on both sides of the reaction. It is a balanced Pb 1 1 chemical reaction. (a) Cu 1/2 1/2 31. A student poured 100 mL of water in a bottle and added 40mL vinegar to it. A balloon was filled with 20g Cl 2 2 baking soda and was fixed at the mouth of the bottle. Slowly the shape of the balloon changed, as shown (b) Pb 1 1 below: Cu 1 1 Cl 1/2 1/2 (c) Pb 1 1 Cu 1 1 Cl 1 1 (d) Pb 1 1 Cu 1 1 Cl 2 2 Ans. Elements Number of Atoms Number of Atoms (d) in Reactants (LHS) in Products (RHS) Pb Cu 1 1 Cl 1 1 2 2

224 CBSE Final Revision of Term-I (Class X) The student claims that a chemical change happened copper is displaced from its solution as copper metal. when the two substances were mixed. Is the claim Hence colour of solution changes. Since silver is less made by the student correct? reactive than copper no change in colour takes place as no displacement reaction takes place. (a) Yes, as a new substance was formed in the form of a gas Pb + CuSO4 → PbSO4 + Cu Ag + CuSO4 → No reaction (b) N o, as the formation of bubbles in the mixture shows a physical change. 34. The chemical reaction between potassium chloride and silver nitrate is given by the chemical equation. (c) Yes, as the mass remains the same throughout the What can be inferred from the chemical equation? experiment. KCl + AgNO3 → AgCl + KNO3 (d) N o, as the change in the shape and size of the balloon shows a physical change. (a) Silver nitrate and potassium undergo a combination reaction to form silver chloride and potassium Ans. (a) Yes, as a new substance was formed in the form of a nitrate. gas. (b) Silver nitrate and potassium undergo a Explanation: decomposition reaction to form silver chloride and potassium nitrate. The mixture forms CO2 and vapours of water a new compound sodium acetate is formed. (c) Silver nitrate and potassium undergo a displacement reaction to form silver chloride and potassium NaHCO3 + CH3COOH → CO2 + H2O + Na+CH3COO– nitrate. Sodium acetic Sodium (d) Silver nitrate and potassium chloride undergo double displacement reaction to form silver chloride bicarbonate acid acetate (new compound) and potassium nitrate. 32. Which of the following statements about the given Ans. (d) Silver nitrate and potassium chloride undergo reaction are correct? double displacement reaction to form silver chloride and potassium nitrate. 3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g) (i) Iron metal is getting oxidised Explanation: Reaction in which positive and negative ions of two (ii) Water is getting reduced ionic compounds exchange places to form two new (iii) Water is acting as reducing agent compounds is called double displacement reaction in the above reaction K+ and Ag+ both exchange their position (iv) Water is acting as oxidising agent with one another, hence it is double displacement. (a) (i), (ii) and (iii) (b) (iii) and (iv) K+Cl– + Ag+ NO3– → AgCl + KNO3 (c) (i), (ii), (iv) (d) (ii) and (iv) Ans. (c) (i), (ii), (iv) Explanation: 3Fe(s) + 4H2O(g) → FeO4(s) + 4H4(g) 35. The reaction between iron oxide and hydrogen is given below : Since oxygen is added to Fe hence it is getting oxidised Fe3O4 + 4H2 → 3Fe + 4H2O and on other hand oxygen is removed from hydrogen Which option shows the compounds undergoing So H2O is getting reduced to H2. Since H2O is getting oxidation and reduction? reduced it act as an oxidising agent for Fe. 33. A students adds lead and silver to two different test Oxidation Reduction tubes containing an equal amount of copper sulphate solution. The student observes that the colour of the solution in the test tube with lead changes. What explains the change in the colour of the solution? (a) A displacement reaction takes place as lead replaces (a) 4H2 Fe2O4 copper from the solution (b) Fe3O4 4H2O (c) 4H2O Fe3O4 (b) Decomposition reaction takes place as copper (d) 3Fe 4H2 dissociates from sulphate in the solution. Ans. Oxidation Reduction (c) A double displacement reaction takes place as copper dissociates from sulphate and lead combines (a) 4H2 Fe2O4 with sulphate in the solution. Explanation: (d) A combination reaction takes place as lead combines Since oxygen is added to Hydrogen to give water and it with sulphate in the solution. removes oxygen from Fe2O4 to give metallic Fe. Ans. (a) A displacement reaction takes place as lead replaces copper from the solution 36. A student notices that the bread kept out has a green coloured coating over it after a few days. What Explanation: explains the reason for the student’s observation? As lead is more reactive than copper hence displaces copper from its solution to form lead sulphate and

Science 225 (a) The oils in the bread reduces and cause the change 6V Bulb in the colour of the bread. battery Switch (b) Bread comes in contact with atmospheric moisture Beaker and corrodes. Nail (c) The oils in the bread oxidises and causes rancidity. Dilute NaOH (d) C omes in contact with the atmospheric nitrogen solution and a layer deposits over it. Rubber cock Ans. (c) The oils in the bread oxidises and causes rancidity. (a) Bulb will not glow because electrolyte is not acidic Explanation: (b) Bulb will glow because NaOH is a strong base and Rancidity is the condition produced by aerial oxidations furnishes ions for conduction. of unsturated fats present in foods marked by unpleasant odour or flavour. In this the unsaturated (c) Bulb will not glow because circuit is incomplete. fats/oils are oxidised. (d) Bulb will not glow because it depends upon the type 37. Calcium oxide reacts vigorously with water to produce of electrolytic solution. slaked lime. CaO(s) + H2O(l) → Ca(OH)2(aq) Ans. (c) Bulb will not glow because circuit is incomplete. This reaction can be classified as: Explanation: (i) Combination reaction (ii) Exothermic reaction Flow of current is essentially needed for the movement (iii) Endothermic reaction of electrons in order to determine the electrical (iv) Oxidation reaction conductivity. Which of the following is a correct option? 40. Identify the correct representation of reaction occurring during chlor-alkali process.[NCERT Exemplar] (a) (i) and (iii) (b) (iii) and (iv) (a) 2NaCl(l) + 2H2O(l) → 2NaOH(l) + Cl2(g) + H2(g) (c) (i), (iii) and (iv) (d) (i) and (ii) (b) 2NaCl(aq) + 2H2O(aq) → 2NaOH(aq) + Cl2(g) + Ans. (d) (i) and (ii)  H2(g) Explanation: (c) 2NaCl(aq) + 2H2O(l) → 2NaOH(aq) + Cl2(aq) + As new product is formed by combination of two H2(aq) compound and as temperature increases due to vigorous reaction so it is a combination reaction along (d) 2NaCl(aq) + 2H2O(l) → 2NaOH(aq) + Cl2(g) + H2(g) with exothermic reaction. Ans. (d) 2NaCl(aq) + 2H2O(l) → 2NaOH(aq) + Cl2(g) + H2(g) Explanation: 38. A sample of soil is mixed with water and allowed to This process uses brine to produce chlorine, sodium settle. The clear supernatant solution turns the pH hydroxide and hydrogen gas in presence of electric paper yellowish-orange. Which of the following would current. change the colour of this pH paper to greenish-blue? 41. Sodium hydrogen carbonate when added to acetic [NCERT Exemplar] acid evolves a gas. Which of the following statements is/are true about the gas evolved? [NCERT Exemplar] (a) Lemon juice (b) Vinegar (i) It turns lime water milky. (ii) It extinguishes a burning splinter (c) Common salt (d) An antacid (iii) It dissolves in a solution of sodium hydroxide. (iv) It has pungent odour. Ans. (d) An antacid Explanation: Solution of soil and water is acidic in nature as shown by (a) (i) and (ii) (b) (i), (ii) and (iii) yellow orange colour of the solution. pH is determined by pH paper. Antacid is a base which is baking soda (c) (ii), (iii) and (iv) (d) (i) and (iv) or sodium bicarbonate or sodium hydrogen carbonate which can change pH from yellow-orange to green Ans. (b) (i), (ii) and (iii) while all others are acidic so no change takes place. Explanation: 39. In an attempt to demonstrate electrical conductivity NaHCO3 + CH3COOH → CH3COONa + H2O + CO2 through an electrolyte, the alongside apparatus was The gas evolved is CO2 which reacts with lime water and turns lime water milky. The gas is acidic in nature set up. Which among the following statement(s) is (are) so dissolves any basic solution like NaOH and dry ice is used in fire extinguisher. correct?  [NCERT Exemplar]

226 CBSE Final Revision of Term-I (Class X) 42. Which of the following is/(are) true when HCl(g) is 1 passed through water?  [NCERT Exemplar] pH α Basic strength α Acidic strength (i) It does not ionise in the solution as it is a covalent 46. A basic solution is added to a test tube. A blue and red compound. litmus paper is dipped into the basic solution. What will happen to both litmus papers? (ii) It ionises in the solution. (a) Blue litmus paper: changes colour; red litmus paper: (iii) It gives both hydrogen and hydroxyl ion in the no colour change solution. (b) Blue litmus paper: changes colour; red litmus paper: (iv) It forms hydronium ion in the solution due to the changes colour combination of hydrogen ion with water molecule. (c) Blue litmus paper: no colour change; red litmus (a) (i) only (b) (iii) only paper: change colour (c) (ii) and (iv) (d) (iii) and (iv) (d) Blue litmus paper: no colour change; red litmus paper: no colour change Ans. (c) (ii) and (iv) Ans. (c) Blue litmus paper: no colour change; red litmus Explanation: paper: change colour. Since HCl is ionic compound Explanation: So HCl + H2O → H3O+ + Cl– Basic solution turns red litmus blue while no change to blue litmus paper takes place in the basic solution. 43. What happens when a solution of an acid is mixed with a solution of a base in a test tube? 47. When hydrogen chloride gas is prepared on a humid (i) Temperature of the solution decreases day, the gas is usually passed through the guard (ii) Temperature of the solution increases tube containing calcium chloride. The role of calcium (iii) Temperature of the solution remains the same chloride taken in the guard tube is to : (iv) Salt formation takes place [NCERT Exemplar] (a) (i) and (iv) (b) (i) and (iii) (a) absorb the evolved gas (b) moisten the gas (c) (ii) only (d) (ii) and (iv) (c) absorb moisture from the gas (d) absorb Cl– ions from the evolved gas Ans. (d) (ii) and (iv) Ans. (c) absorb moisture from the gas Explanation: Explanation: Calcium chloride acts as a dehumidifer for the reaction. Acid reacts with base to form salt and water this is neutralisation reaction which is exthermic in nature. Hence temperature of reaction mixture increases. 44. A solution of pH 2 is filled in two separate beakers. A 48. When dilute sulphuric acid is added to a solid X, a gas few drops of methyl orange and phenolphthalein are Y is formed along with the formation of the salt of the added into separate solutions. How will the colour of solid. What could be X and Y? the indicators change? (a) X: carbon; Y:hydrogen (b) X: zinc; Y: hydrogen (a) Methyl orange: red; phenolphthalein: pink (c) X: zinc; Y: oxygen (d) X: copper; Y: oxygen (b) Methyl orange: orange; phenolphthalein: colourless (c) Methyl orange: red; phenolphthalein: colourless Ans. (b) X: zinc; Y: hydrogen (d) Methyl orange: orange; phenolphthalein: pink Ans. (c) Methyl orange: red; phenolphthalein: colourless Explanation: Explanation: The solution having pH = 2 is acidic in Nature. X + H2SO4(dil.) → Y(g) + Salt. Zn + H2SO4 (dil.) → H2 + ZnSO4 45. Which of the following statements is/are correct Zinc reacts with dilute sulphuric acid to form zinc about an aqueous solution of an acid or a base? sulphate which is soild in nature along with the evolution (i) Higher the pH, stronger the acid of hydrogen gas. (ii) Higher the pH, weaker the acid (iii) Lower the pH, stronger the base 49. When a base reacts with a metal, it forms a salt (iv) Lower the pH, weaker the base [NCERT Exemplar] and hydrogen gas is released. By what method the presence of hydrogen can be detected? (a) By methyl orange (b) By water (c) By litmus paper (d) By a burning candle (a) (i) and (iii) (b) (ii) and (iii) Ans. (d) By a burning candle (c) (i) and (iv) (d) (ii) and (iv) Ans. (d) (ii) and (iv) Explanation: Explanation: When a burning candle is brought near the mouth of test tube the gas evolued burns with a pop sound indicating the gas is hydrogen gas.

Science 227 50. A student did an activity in which he added sodium (b) B E bicarbonate to hydrochloric acid. It forms the carbon dioxide gas. The gas released is passed through lime (c) A C water. What change will be observed in lime water? (d) B C (a) A – E (b) B – C (a) The colour of solution becomes red. (c) A – E (d) A – C (b) White precipitate is formed. Ans. (a) A – E (c) The solution becomes colourless. Explanation: For solution pH > 7 acidic, pH > 7 basic, pH = 7 neutral (d) Bubbles are formed. Ans. (b) White precipitate is formed. 54. Single circulation, i.e., blood flows through the heart only once during one cycle of passage through the Explanation: body, is exhibited by  [NCERT Exemplar] CaO + CO2 → CaCO3 Lime water Calcium carbonate (a) Labeo, Chameleon, Salamander When CO2 gas is passed through it turns lime water (b) Hippocampus, Exocoetus, Anabas milky and white precipitate of calcium carbonate is (c) Hyla, Rana, Draco formed. (d) Whale, Dolphin, Turtle 51. An oxide of element P is added to an acid where it forms salt and water. The table shows the possible Ans. (b) Hippocampus, Exocoetus, Anabas value of pH and the type of element before the Explanation: reaction.  Single circulation is exhibited by those, organisms S.No. pH Type of Element which have two chambered heart (one auricle and one Metal ventricle).Therefore two single circulations are found in A Less than 7 Anabas, Exocoetus and hippocampus. Non-metal B Less than 7 Metal C Greater than 7 Non-metal 55. The equation shows the reaction of hydrochloric acid with sodium hydroxide. D Greater than 7 HCl + NaOH → NaCl + H2O Which option is correct? If the pH of the salt is 7, what are the positive and (a) A (b) D negative redicals in the salt? (c) C (d) B Ans. (a) A (a) Na - negative radical; Cl - negative radical Explanation: (b) Na - positive radical; Cl-negative radical (c) Na - positive radical; Cl-positive radical The more acidic substances usually forms, metal. (d) Na - negative radical; Cl-positive radical Ans. (b) Na - positive radical; Cl-negative radical 52. If salivary amylase is lacking in the saliva, which of the Explanation: following events in the mouth cavity will be affected? NaCl + H2O → Na+ + Cl– [NCERT Exemplar] Sodium is positive radical and chloride is negative radical. (a) Proteins breaking down into amino acids (b) Starch breaking down into sugars 56. A student sets up an experiment to study the (c) Fats breaking down into fatty acids and glycerol importance of nutrition in plants. The student takes 2 (d) Absorption of vitamins pots, pot 1 and pot 2 each with the same healthy plant. Ans. (b) Starch breaking down into sugars. Both the pots were placed in the garden and watered Explanation: properly. Pot 1 was kept as such, while pot 2 was kept Amylase is enzyme catalysis hydrolysis of starch into in an air tight glass box with caustic soda. Caustic soda. simple sugar, so if enzyme salivary amlyase is lacking in Caustic soda absorbs carbon dioxide present in saliva then the breakdown of starch is affected. the surrounding. After 2 days, the student observes that the plant kept in the garden is healthy while the 53. Five solutions are labelled on a pH scale. plant placed in container shed leaves and droops. What is the likely reason for this observation? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 (a) Absence of oxygen for survical ↑ ↑ ↑ ↑ ↑ (b) Absorption of light by caustic soda restricting A B C D E growth Which classification is correct? (c) Inability to perform photosynthesis Strongest Acid Strongest Base (d) Lack of nutrients in the soil (a) A E

228 CBSE Final Revision of Term-I (Class X) Ans. (c) Inability to perform photosynthesis tube. No change occurred in test tubes A and B but Explanation: Photosynthesis is the process by which green plants the metal got dissolved in test tube C respectively. The prepare their own food in presence of sunlight. metal could be:  [NCERT Exemplar] (a) Al (b) Au 57. The chemical reaction shows the reactants for the (c) Cu (d) Pt formation of baking soda. Ans. (b) Au NaCl + H2O + CO2 + NH3 → X + Y What are X and Y?  Explanation: (a) X: NH3Cl; Y: NaHCO3 (b) X: NH4Cl; Y: NaHCO3 Aqua region is the mixture to test nobel metals which is (c) X: HCl; Y: NaHCO3 (d) X: NH4Cl; Y: NaHCO2 mixture of three parts of concentrated HCl and one part Ans. (b) X: NH4Cl; Y: NaHCO3 of concentrated nitric acid and is capable of dissolving Explanation: gold. Gold cannot be dissolved in dilute acids and it only dissolves concentrated acids. NaCl + H2O + CO2 + NH3 → NH4Cl + NaHCO3 61. Which among the following statements is incorrect for magnesium metal?  [NCERT Exemplar] 58. What happens when calcium is treated with water? (a) It burns in oxygen with a dazzling white flame. [NCERT Exemplar] (b) It reacts with cold water to form magnesium (i) It does not react with water. hydroxide and evolves hydrogen gas. (ii) It reacts violently with water. (iii) It reacts less violently with water. (c) It reacts with hot water to form magnesium (iv) Bubble of hydrogen gas formed stick to the surface hydrodixe and evolves hydrogen gas. of calcium. (d) It reacts with steam to form magnesium hydroxide and evolves hydrogen gas. (a) (i) and (iv) (b) (ii) ahnd (iii) Ans. (b) It reacts with cold water to form magnesium hydroxide and evolves hydrogen gas. (c) (i) and (ii) (d) (iii) and (iv) 62. Assertion: Presence of HCl in stomach is necessary for the process of digestion. Ans. (d) (iii) and (iv) Reason: HCl kills and inhibits the growth of bacteria in Explanation: the stomach. Reaction between calcium and water is Ans. (B) B oth A and R are true, but R is not the correct explanation of A. H2O + Ca+2 → CaO + H2↑ Explanation: Metal reacts with water to form metallic oxides along with evolution of hydrogen gas. This reaction is less Presence of HCl in stomach is necessary for digestion violent and less vigrous as compared to other. The because acidic medium activates the action of gastric hydrogen gas evolved burns with a pop sound and sticks juice. HCl maintains a strong acidic pH, of about 1-2 in to surface of metal (Ca) the stomach. HCl helps to activate Pepsinogen to pepsin which digests proteins to peptones and proteases. HCl 59. The composition of aqua regia is: inhibits the growth and also kills the germs that may have entered the stomach along with the food. So, thus (a) Dil. HCl : Conc HNO3 it can be said that HCl kills bacteria but that does not 3 : 1 help in digestion. Thus both assertion and reason are true, but reason is not the correct explanation of the (b) Concl. HCl : Dil. HNO3 assertion. 3 : 1 63. Assertion: Sodium is kept immersed in kerosene oil. (c) Conc. HCl : Conc. HNO3 Reason: Sodium is very reactive metal. 3 : 1 (d) Dil. HCl : Dil. HNO3 3 : 1 Ans. (c) Conc. HCl : Conc. HNO3 Ans. (A) B oth A and R are true and R is the correct explanation 3 : 1 of A. Explanation: Explanation: It is a yellow-orange fuming liquid having HNO3 : HCl Sodium is a very reactive metal. It reacts so vigorously ratio of 1 : 3. that it catches fire if kept in the open. Therefore, to prevent the accidental fires, it is kept immersed in 60. 2 mL each of concentrated HCl, HNO3 and a mixture kerosene oil. Thus, both assertion and reason are true of concentrated HCl and concentrated HNO3 in the and reason is the correct explanation of the assertion. ratio of 3 : 1 were taken in test tubes labelled as A, B and C. A small piece of metal was put in each test 64. Assertion: Sodium hydroxide reacts with zinc to produce hydrogen gas.

Science 229 Reason: Acids reacts with active metals to produce Explanation: hydrogen gas. The chemical equations should be balanced because as Ans. (B) B oth A and R are true but R is not the correct per the law of conservation of mass—“mass can neither explanation of A. be created nor be destroyed”. Therefore number of atoms on both the sides of the equations should be Explanation: equal. Thus both assertion and reason are true and reason is the correct explanation of the assertion. Sodium hydroxide being an strong base, reacts with active metal (zinc) to produce H2 gas. The reaction is 69. A student adds some metallic ash in water in a test given as follows : tube. The ash gets completely dissolved in water and the solution changes colour. What should the student Zn(s) + 2NaOH(aq) →Na2ZnO2(aq) + H2(g) do next to test the chemical properties of the product Thus both assertion and reason are true, but reason is formed? not the correct explanation of the assertion. (a) Test the acidity using a blue litmus paper. 65. Assertion: The nature of the image formed by a concave (b) Test the basicity using a red litmus paper. mirror is real and inverted. (c) Measure the temperature change using a Reason: The image formed by a concave mirror depends thermometer. on the position of the object at infinity. (d) Evaporate the solution to get crystals. Ans. (A) Both A and R are true and R is the correct explanation of A. Ans. (b) Test the basicity using a red litmus paper. Explanation: Explanation: Metellic ashes means that there is formation of metal When the object is placed at an infinity position, the oxide taking place when metal is heated in presence of image formed by a concave mirror will be placed at oxygen. Metal oxides are generally basic in nature. Thus the focus. Then the size of the image will be highly we should check basicity using red litmus paper. diminished and point-size. So, the nature of the image formed by the concave mirror is real and inverted. Thus, 70. The chemical reaction between a piece of copper and both assertion and reason are correct and reason is the nitric acid is given by the chemical equations, correct explanation of the assertion. Cu + HNO3 → Cu(NO3)2 + H2 66. Choose the incorrect one: H2 + HNO3 → H2O + NO2 (a) An ionic bond represents sharing of electrons What can be inferred from the chemical equation? (b) Metals are electropositive [CBSE Question Bank] (c) Non-metals are electronegative (a) Nitrate reacts with hydrogen to form NO2 and H2O. (b) Hydrogen gas gets oxidized by HNO3 to form water. (d) Atoms react in order to complete their octet (c) Gas reacts with oxygen in the air to form water. Ans. (a) An ionic bond represents sharing of electrons (d) Copper causes the oxidation of HNO3 to form NO2. Ans. (b) Hydrogen gas gets oxidized by HNO3 to form water. 67. An object is placed at the centre of curvature of a concave Explanation: mirror. The distance between its image and pole is: (a) equal to f (b) between f and 2f (c) equal to 2f (d) greater than 2f Ans. (c) equal to 2f Addition of oxygen to a compound is called oxidation Explanation: An object is at C, since O2 is added to hydrogen to form water. So H2 is oxidised by HNO3 to form H2O. u = – C = – 2f Mirror formula, 1 11 71. Which among the following is /(are) double f u v displacement reaction(s)?  [NCERT Exemplar] For concave mirror, f is negative (i) Pb + CuCl2 PbCl2 + Cu −1  1 1 (ii) Na2SO4 + BaCl2 BaSO2 + 2NaCl f 2f v (iii) C + O2 CO2 1  1  1 1 v f 2f 2f (iv) CH4 + 2O2 CO2 + 2H2O v = – 2f (a) (i) and (iv) (b) (ii) only Distance of image from pole is 2f. (c) (i) and (ii) (d) (iii) and (iv) 68. Assertion (A): Chemical equations should be balanced. Ans. (b) (ii) only Reason (R): As per the law of conservation of mass, mass can neither be created nor be destroyed. Explanation: Ans. (A) A and R are true and R is the correct explanation of A reaction in which positive and negative ions of two A. ionic compounds exchange places to form two new compounds is called double-displacement reaction. Since in reaction (ii) two ionic compounds are involved

230 CBSE Final Revision of Term-I (Class X) and also exchange their position. Hence it is an example of double displacement reaction. 72. The pH values of four solutions on a pH scale are shown below.  [CBSE Question Bank] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 ↑ ↑ ↑ ↑ A B C D Which solutions are alkaline in nature? (a) A and B (b) A and D (c) C and D (d) B and C Ans. (c) C and D Explanation: (a) Plant absorb CO2 from air and H2O from the soil as raw materials and convert them into glucose. For basic or alkaline solution pH > 7. (b) Plants absorb O2 from air and minerals from the soil 73. Which of the following is most appropriate for aerobic as raw materials and convert them into heat energy. respiration?  [NCERT Exemplar] (c) Plants absorb O2 from air and glucose from the (a) Glucose Mitochondriao Pyruvate Cytoplasmo soil as raw materials and convert them into lilght energy. CO2 + H2O + Energy (b) Glucose Cytoplasmo Pyruvate Mitochondriao (d) Plants absorb CO2 from the soil and H2O from air as raw materials and convert them into glucose. CO2 + H2O + Energy (c) Glucose Cytoplasmo Pyruvate + Energy Ans. (a) Plant absorb CO2 from air and H2O from the soil as raw materials and convert them into glucose. Mitochondriao CO2 + H2O (d) Glucose Cytoplasmo Pyruvate + Energy 76. Assertion: The rate of photosynthesis will be lowered if the leaves are coated with oil. Mitochondriao CO2 + H2O + Energy Ans. (d) Glucose Cytoplasmo Pyruvate + Energy Reason: Stomata gets blocked and thus gaseous exchange is affected. Mitochondriao CO2 + H2O + Energy Ans. (A) A and R are true and R is the correct explanation of Explanation: A. An Aerobic respiration is respiration that occurs in the Explanation: presence of oxygen in the cytoplasm. Stomata is a tiny pore in leaves that help in gaseous 74. A sting from insect A has pH of 6. The table shows the exchange, so if the stomata gets blocked due to oil, pH of four substances. gaseous exchange will be affected and hence rate of photosynthesis gets lowered. Thus both assertion and Which substance is used to treat the sting? reason are true and reason is the correct explanation of [CBSE Question Bank] the assertion. Substance pH 77. Assertion (A): When a piece of copper metal is added to Hydrochloric acid 1 dilute sulphuric acid, the solution turns blue. Vinegar 5 Sodium hydrogen carbonate 8 Reason (R): Copper reacts with dilute sulphuric acid to Sodium hydroxide 14 form copper (II) sulphate solution (a) Vinegar Ans. (A) B oth A and R are true and R is the correct explanation (b) Sodium hydroxide of A. (c) Sodium hydrogen carbonate (d) Hydrochloric acid Explanation: Ans. (c) Sodium hydrogen carbonate Explanation: When a piece of copper metal is added to dilute pH = 6 acidic for treating a base should be used, suchas sulphuric acid, the solution turns blue. It is because, sodium hydrogen carbonate. copper reacts with dilute sulphuric acid to form blue copper 75. The image shows the process of making food by a plant. (II) sulphate solution. Thus both assertion and reason are true and reason is the correct explanation of the Which statement can be concluded from the image? assertion. 78. Assertion (A): The air bubble shines in water. Reason (R): Air bubble in water shines due to refraction of light. Ans. (C) A is true but R is false.

Science 231 Explanation: (b) Saliva will convert starch into complex fat molecules. Shining of air bubble in water is on account of total (c) Saliva will breakdown starch into simple sugar internal reflection. Thus, assertion is true but reason is molecules. false 79. What is the energy currency of the cell? (d) Saliva will convert starch into complex sugar (a) Adenosine triphosphorous molecules. (b) Adenosine tetraphosphorous (c) Adenosine triphosphate Ans. (c) Saliva will breakdown starch into simple sugar (d) Adenosine diphosphate molecules. Ans. (c) Adenosine triphosphate 80. A student obtains a blurred image of a distant object on Explanation: a screen using a convex lens. To obtain a distinct image on the screen he should move the lens : Saliva present in salivary amylase works on simple sugar (a) away from the screen molecules, proteinase works on breakdown of proteins. (b) towards the screen Digestion is breakdown of complex sugar into simple (c) to a position very far away from the screen. ones. So saliva in mouth breaks starch into simple (d) either towards or away from the screen depending sugars. upon the position of the object. 83. A student sets up an experiment to study the role of Ans. (b) towards the screen enzymes in digestion of food. Explanation: As in order to get a sharp image the screen should be Egg white Egg white + pepsin + pepsin + HCl near to lens. 81. The image shows a cross section of small intestine. AB What will be the likely happen if the number of villi In which test tube, the digestion of protein will occur? increases in the intestine? (a) Test tubes A as pepsin will breakdown protein into simple molecules. Villi (b) Test tubes B as HCl will breakdown protein into Blood vessels simple molecules. (a) Increase in the absorption of food. (b) Fast breakdown of larger food particles into smaller (c) Test tubes A as pepsin will breakdown into simple molecules. ones. (c) Increase in flow of blood in the small (d) Test tubes B as HCl will activate pepsin for breakdown of protein into simple molecules. intestine. (d) Fast elimination of waste from the body. Ans. (d) Test tubes B as HCl will activate pepsin for Ans. (a) Increase in the absorption of food. breakdown of protein into simple molecules. Explanation: Villi are small firger like projections present in small Explanation: interstine and are mainly concerned with the process of adsorption of food with increase in number of villi For complete digestion of protein a proteolytic the rate of adsorption increases as surface area for enzyme like pepsin is used which works at appropiate adsorption also increases. temperature and low pH (1.5-3.5). Hence HCl acid 82. An incomplete equation for the digestion of starch is added to activate pepsin once all conditions are using salvia is shown as: presence digestion of protein takes place. So digestion Saliva + Starch (in test tube) → of protein takes in B where HCl is added to make What will be the likely outcome of this? medium acidic to activate pepsin, enzyme. (a) Saliva will breakdown starch into simple protein 84. Which pathway will occur in the cell of an athlete who molecules. is performing 100 m sprint? (a) Glucose InCytoplasmo Pyruvate Absence of oxygeno Ethanol + CO2 + Energy (b) Glucose InCytoplasmo Pyruvate Lackofof oxygeno Lactic acid + Energy (in human muscle cells)

232 CBSE Final Revision of Term-I (Class X) (c) Glucose InCytoplasmo Pyruvate Ans. (b) Living beings consumes oxygen during respiration. Lack of oxygen Lactic acid Explanation: (in human + Engery Both candle and living organism require O2. Candle require O2 for combution while cockroach for muscle cells) respiration since in A both uses available O2 hence candle extinguish faster as in B. Presence of oxygen CO2 + Water (in mitochondria) + Engery 86. A student sets up an experiment to study human respiration using lime water, test tube and a straw. Lime (d) Glucose InCytoplasmo Pyruvate water is colourless in the absence of CO2 and is milky in its presence. The student fills a freshly prepared Lack of oxygen Lactic acid limewater in a test tube and blows air through straw into the limewater. It was observed that the solution (in human + Engery turns cloudy as shown. muscle cells) What can be evaluated from this observation? Presence of oxygen Ethanol + CO2 (in human muscle + Energy cells) Ans. (c) Glucose InCytoplasmo Pyruvate Lack of oxygen Lactic acid (in human + Engery muscle cells) Presence of oxygen CO2 + Water (in mitochondria) + Engery Explanation: There are two energy systems in human body: (a) Anaerobic respiration (Slow uses carbohydrate) (b) Aerobic respiration (Uses carbohydrate or fat) In anaerobic Glucose InCytoplasmo Pyruvate Pyruvate Lack of oxygen Lactic acid (a) Oxygen is exhaled during respiration. + Engery (ATP) (b) Water vapours are produced during respiration. In muscle Ethanol + CO2 + cells Energy (ATP) (c) Carbon dioxide is exhaled during respiration. 85. A student setup an experiment to study the human (d) Glucose is produced during respiration. respiratory system. In the experiment, the student places candle and a living cockroach in the flask A, Ans. (c) Carbon dioxide is exhaled during respiration. while a candle and a dead cockroach in flask B. The burning of candle needs oxygen. Explanation: Conical Rubber cork Rubber Respiration is a process by which living organisms take flask Wire in O2 and give out CO2 out of body. As lime water cork turns milky it indicates that CO2 is exhaled out during Conical Wire respiration and O2 is inhaled during respiration. flask 87. The diagram shows part of the human respiratory system. Living Candle Dead Candle cockroach cockroach After 10 minutes, the student observe that the candle in flask A extinguish faster while candle in flask B keeps burning for a longer time. What can be evaluated from this experiment? (a) Water vapours produced by living beings prevents What are W, X, Y and Z ? burning of candle. (a) B ranches-W, Bronchiole-X, Larynx-Z, Rings of (b) Living beings consumes oxygen during respiration. cartilage-Y (c) Burning of candle decreases the life span of (b) Branches-X, Bronchiole-Z, Larynx-Y, Rings of cockroach. cartilage-W (d) Candle produces high amount of carbon dioxide

Science 233 (c) Branches-Y, Bronchiole-W, Larynx-X, Rings of 90. In which order do these events occur in human cartilage-Z nutrition? (d) Branches-Z, Bronchiole-Y, Larynx-W, Rings of (a) Digestion → ingestion → absorption → assimilation cartilage-X (b) Digestion → ingestion → assimilation → absorption Ans. (d) Branches-Z, Bronchiole-Y, Larynx-W, Rings of cartilage-X (c) Ingestion → digestion → absorption → assimilation Explanation: (d) Ingestion → digestion → assimilation → absorption Larynx is at the beginning of trachea. After trachea, Ans. (c) Ingestion → digestion → absorption → assimilation bronchi are found which further branch into bronchioles. 88. The diagram shows a vertical section through the heart. Explanation: What are the functions of the numbered blood vessels? After ingestion, food is digestd in buccal cavity, stomach (a) Carries blood to body-1, Carries blood to lungs-2, and small intestine. Then the producs of digestion, i.e., Carries blood from lungs-3, Carries blood from glucose and amino acids are absorbed from the ileum body-4 region into the blood which carries these products to (b) Carries blood to body-1, Carries blood to lungs-3, body tissues and cells where assimilation occurs. Carries blood from lungs-4, Carries blood from body-2 91. Assertion: Hydrogen peroxide is kept in coloured (c) Carries blood to body-2, Carries blood to lungs-4, bottles. Carries blood from lungs-3, Carries blood from body-1 Reason: Hydrogen peroxide is a moderately reactive metal that can react with light or heat slowly to produce (d) Carries blood to body-3, Carries blood to lungs-1, water. Carries blood from lungs-4, Carries blood from body-2 Ans. (c) A is true but R is False. Ans. (d) C arries blood to body-3, Carries blood to lungs-1, Explanation: Carries blood from lungs-4, Carries blood from body-2 Hydrogen peroxide is a highly reactive metal that can react with light or heat to produce water. It decomposes Explanation: into water and oxygen in the presence of sunlight. Vessel 1 is pulmonary artery and carries blood to lungs. Vessel 2 is vena cava and carries blood from body to To prevent this reaction with light and heat it is stored in coloured bottles so that light cannot pass through it. heart. Thus assertion is true but reason is false. Vessel 3 is aorta and carries blood from heart to body. Vessel 4 is pulmonary vein and carries blood from lungs 92. Assertion: The nature of the image formed by a concave mirror is real and inverted. to heart. 89. In which of the following groups of oragnism, food Reason: The image formed by a concave mirror depends on the position of the object at infinity. material is broken down outside the body and absorbed? (a) Mushroom, green plants, Amoeba Ans. (A) B oth A and R are true and R is the Correct explanation (b) Yeast, mushroom, brad mould of A. (c) Paramecium, Amoeba, Cuscuta (d) Cuscuta, lice, tapeworm Explanation: Ans. (d) Yeast, mushroom, brad mould Explanation: When the object is placed at an infinity position, the These are saprotrophs and digestion in saprotrophs take image formed by a concave mirror will be placed at place before ingestion. They break down and convert the focus. Then the size of the image will be highly complex organic molcules present in dead and decaying diminished and point-size. So, the nature of the image matter into simpler substances outside their body. formed by the concave mirror is real and inverted. Thus both assertion and reason are true and reason is the correct explanation of assertion. 93. Assertion: Urinary bladder and ureters are lined by transitional epithelium. Reason: Ureters carry the urine to urinary bladder where it is stored temporarily. Ans. (B) A and R is true but R is not the correct explanation of A. Explanation: Ureters function is to carry urine from kidney to the bladder, it does not depend on what lining it has. Thus both assertion and reason are true, but reason is not the correct explanation of assertion. 94. How is sex of a child determined? Give reason. (a) The X chromosome in the zygote (b) The Y chromosome in zygote

234 CBSE Final Revision of Term-I (Class X) (c) The cytoplasm of germ cell which determines the which dissociates into H+ and Cl– ion these solutions do sex not dissociate into ions. Thus both assertion and reason are true and reason is the correct explanation of the (d) Sex is determined by chance assertion. Ans. (B) The Y chromosome in zygote 99. Which of the following statement(s) is /(are) true about Explanation: As X chromosomes from mother and Y chromosomes heart?  [NCERT Exemplar] from father in the zygote as XY chromosme determines (i) Left atrium receives oxygenated blood from the boy child. different parts of body while right atrium receives deoxygenated blood from lungs. 95. Which one of the following properties is not generally exhibited by ionic compounds ? (ii) Left ventricle pumps oxygenated blood to different body parts while right ventricle pumps (a) Solubility in water deoxygenated blood to lungs. (b) Electrical conductivity in solid state (iii) Left atrium transfers oxygenated blood to right ventricle which sends it to different body parts. (c) High melting and boiling points (iv) Right atrium receives deoxygenated blood from (d) Electrical conductivity in molten state different parts of the body while left ventricle pumps oxygenated blood to different parts of the Ans. (b) Electrical conductivity in solid state. body. Explanation: Ionic compounds can conduct electricity in aqueous (a) (i) (b) (ii) (c) (ii) and (iv) (d) (i) and (iii) solution or molten state. Ans. (c) (ii) and (iv) In solid state, they are non-conductors of electricity 100. Choose the correct statement that describes arteries. because of the absence of free ions. [NCERT Exemplar] 96. The cross-sectional diagram of a flower is given below. Choose the correct statement. (a) They have thick elastic walls, blood flows under high pressure, collect blood from different organs and A bring it back to the heart. B (b) They have thin walls with valves inside, blood flows G under low pressure and carry blood away from the heart to various organs of the body HE (c) They have thick elastic walls, blood flows under C low pressure; carry blood from the heart to various I organs of the body. F (d) They have thick elastic walls without valves inside, blood flows under high pressure and carry blood Ans. (c) Female reproductive parts: A, E, G, I Male away from the heart to different parts of the body. reproductive parts: B, C, H. Ans. (d) They have thick elastic walls without valves inside, 97. Which process occurring in human body does not blood flows under high pressure and carry blood involve energy from respiration? away from the heart to different parts of the body. (a) Contraction of heart muscle 101. The graph below represents the blood lactic acid concentration of an athlete during a race of 400 m and (b) Diffusion of oxygen from the alveoli into the blood shows a peak at point D. (c) Digestion of bread Respiration in arthlete The blood of an athlete was tested (d) Maintaining a constant body temperature before, during and after a 400 m race 12 D Ans. (b) Diffusion of oxygen from the alveoli into the blood Blood lactic acid concentration (in mol/litre) 10 Explanation: 8E Exchange of O2 and CO2 at the site of alveoli occurs 6 C due to diffusion gradient as the inhaled air carries B more O2 than blood and blood contains more CO2 than the atmospheric air. Processes in other options are all 4 energy requiring. 2A 98. Assertion: Solutions of compounds like alcohol and glucose do not show acidic character. 0 30 60 Time in seconds Reason: They do not show acidic character because they do not dissociate into ions. Ans. (a) Both A and R are true and R is the correct explanation of A. Explanation: Solutions of compounds like alcohol and glucose do not show acidic character because like acids such as HCl

Science 235 Lactic acid production has ocurred in the athlete while The Average Rate of Blood Flow through the Blood VesselsRate of Blood Flow in cm/s running in the 400 m race. Which of the following Aorte processes explains this event? 45 Arteries 40 Arterioles (a) Aerobic respiration 35 Capillaries 30 Venules (b) Anaerobic respiration 25 Veins 20 Vena Cava (c) Fermentation 15 10 (d) Breathing 5 Ans. (b) Anaerobic respiration 0 Explanation: The rate of blood flow in the capilaries is very low because capillaries are Lactic acid is a chemical byproduct of anaerobic respiration the process by which cells produce energy without oxygen. 102. The figure shows blood circulation in humans with labels A to D. Select the option which gives correct identification of label and functions of the part. D (a) very narrow and have high resistance (b) much wide and have low resistance RA LA (c) very narrow and have low resistance RV LV (d) much wide and have high resistance Ans. (a) very narrow and have high resistance C Lumen A Body parts Explanation: B The diameter of capillaries is very narrow and they have high resistance. Therefore, blood flows more slowly (a) B-Capillary-Thin without muscle layer and wall two through them. They are narrow as they are responsible cell layers thick for exchange of gases at organ level so has to reach each and every organ of body they are narrow and have (b) C-Vein-Thin walled and blood flows in jerks/spurts high resistance. (c) D-Pulmonary vein-Takes oxygenated blood to heart, 104. Choose the correct combination to depict the given PO2 = 95 mm Hg figure: (d) A-Artery-Thick walled and blood flows evenly Pressure in cuff Pressure in cuff below 120 below 70 Ans. (c) D-Pulmonary vein-Takes oxygenated blood to heart, PO2 = 95 mm Hg 120 70 Explanation: A - A rtery, carries blood from heart to different body part. B - Capillary, one cell layer thick. (x) (y) C - vein, brings blood from different body parts to heart. (a) x. Systolic pressure, y. Systolic pressure (b) x. Systolic pressure, y. Diastolic pressure D - pulmonary vein, transport oxygenated blood to left (c) x. Diastolic pressure, y. Systolic pressure atrium. (d) x. Diastolic pressure, y. Diastolic pressure Ans. (b) x. Systolic pressure, y. Diastolic pressure 103. The given graph indicates the average rate of blood flow in the different blood vessels.

236 CBSE Final Revision of Term-I (Class X) 1 05. (i) The site of ultrafiltration (ii) Collect the urine and make it more concentrated X (iii) T he main site for the reabsorption of glucose and amino acids (iv) L argely responsible for the maintenance of blood Study the picture given above and choose the correct combination of information provided in the following pH table. (a) (i)-A, (ii)-E, (iii)-C, (iv)-D X Process Function (b) (i)-A, (ii)-B, (iii)-C, (iv)-D used (c) (i)-B, (ii)-A, (iii)-C, (iv)-E (d) (i)-E, (ii)-B, (iii)-D, (iv)-A (a) Dialyser Diffusion To remove the excess Ans. (a) (i)-A, (ii)-E, (iii)-C, (iv)-D wastes and fluid from the Explanation: blood Glomorous is the site of ultrafiltration which is (b) Blood thinner Cotting To remove the clots from represented by A in diagram the collecting duct collect the blood urine from all parts of body and makes it concentrated represented by E in figure. The first segment of renal (c) Dialysate Osmosis To add fluid to the blood tubule known as Proximal Convoluted Tubule (PCT) is mainly responsible for reabsorption of glucose and (d) Dialysing Filtration To draw blood from amino acids from urine represented by C. pump the body and send it to dialyser. 107. The graph given below shows the extent to which carbohydrates, proteins and fats are chemically Ans. digested as food passes through the human digestive tract. The letters represent the sequential structures X Process Function that make up the digestive tract. used Key: (a) Dialyser Diffusion To remove the excess Fats wastes and fluid from the Proteins blood Carbohydrates 100 The given picture represents the process of Percent of undigested 50 haemodialysis where ''X'' is denoting the dialyser. A molecules present dialyser is often referred to as an ''artificial kidney.'' Its function is to remove the excess wastes and fluid from 0A B C D EF the blood when the patient's kidneys can no longer (Mouth) (Anus) perform that task. During this passage, the waste products from the blood passes into dialysing fluid by Proteins are digested in both diffusion. 106. The given figure represents a single nephron from a (a) A and B (b) B and C mammalian kidney. Identify the labelled parts, match them with the options (I-IV) and select the correct (c) C and D (d) A and D answer. Ans. (c) C and D Explanation: The first graph shows maximal activity at a very acidic pH, implying that this is an enzyme acting in the stomach. The second graph shows maximal activity around pH 8.5, implying that this is an enzyme acting in the duodenum. The only choice that matches the first graph with a stomach enzyme, i.e., pepsin and the second with a duodenal enzyme, i.e., carboxypeptidase. Here, A represents mouth, B represents oesophagus, C represents stomach, D represents small intestine and E represents large intestine. The digestion of protein begins in the stomach and is completed in the small intestine.

Science 237 108. In the following columns, the position of an object is (d) given in Column I and the nature of image formed in a Ans. (d) concave mirror is given in Column II: C FP Column (I) Column (II) (Position of object) (Nature of image) A. At infinity (p) Real B. Between infinity and (q) Inverted centre of curvature C. At centre of curvature (r) Diminished C FP D. At focus (s) Enlarged Explanation: (t) Same size In the case of a concave mirror, an incident ray is parallel to A B C D the principal axis and it passes through F after reflection. (a) p, q q (b) r, s q, r r, s q, r 110. A child is standing in front of a magic mirror. He finds (c) p, s q the image of his head bigger, the middle portion of his (d) p, q, r p, q, r s, t p, q, r, s body to be of same size and that of the legs smaller. Ans. (d) p, q, r p, q, r Which of the following is the order of combination for r, s, t r the magic mirror from the top? [NCERT Exemplar] p, q, r p, q (a) Plane, convex and concave (b) Concave, plane and convex p, q, r p, q (c) Concave, plane and convex (d) Convex, plane and concave 109. Which of the following ray diagrams is correct for the Ans. (c) Concave, plane and convex ray of light incident on a concave mirror as shown in Explanation: Figure?  [NCERT Exemplar] As image of head is bigger, the top portion of magic mirror must be concave. The middle portion of her body C FP appears to be of same size, therefore, middle portion of (a) magic mirror must be plane. As image of her legs appears smaller, the bottom of magic mirror must be convex. C FP 1 11. The distance between the optical centre and point of convergence is called focal length. In which of the following cases it is correctly shown? (a) (b) 2F F P (b) (c) (c) 2F F P (d)

238 CBSE Final Revision of Term-I (Class X) Ans. (c) 114. Figure shows a ray of light as it travels from medium A to medium B. Refractive index of the medium B relative to medium A is: Explanation: 45º Medium B Parallel rays after refraction meet at the focus of a 45º convex lens. 60º30º Medium A 1 12. A student does the experiment on tracing the path of 3 (b) 2 a ray of light passing through a rectangular glass slab (a) for different angles of incidence. He can get a correct 3 measure of the angle of incidence. He can get a correct 2 measure of the angle of incidence and the angle of 1 emergence by following the labelling indicated in figure (c) 2 ii (d) 2 (A) e (B) e 3 i i Ans. (a) (D) e 2 (b) B Explanation: (d) D µ ==ssiinnri s=in60º 3 /2 sin 45º 1/ 2 e 3 = (a) A (c) C 2 i 115. Which one of the following ray diagrams is correct for the ray of light incident on a lens as shown in figure? [NCERT Exemplar] Ans. (d) F1 O F2 e Explanation: (a) O F2 F1 Angle of incidence and energance are measured w.r.t the normal drawn at the surface. (b) 1 13. Which of the following statements is correct regarding the propagation of light of different colours of white light in air?  [NCERT Exemplar] (a) Red light moves fastest. F1 O F2 (b) Blue light travels faster than green light. (c) (c) All colours of white light move with the same speed. F1 O F2 (d) Yellow light moves with the mean speed as that of red and violet lights. Ans. (c) All colours of white light move with the same speed. Explanation: It only gets deviated when it passes through a medium.

Science 239 (d) Where would the reflected rays meet for the image F1 O F2 formation to take place? (a) Between F and O (b) Beyond C Ans. (b) (c) Between C and F (d) Behind the mirror Ans. (c) Between C and F Explanation: A F1 O F2 C B' F B Explanation: A' A ray after passing through the focus of convex lens and refraced from lens then it goes parallel to the principle axis. 1 18. An object is placed near a concave mirror at a distance of one-fourth the radius of curvature of the concave 116. The image shows reflection of light on a mirror. mirror. Which ray diagram shows the incident rays, reflected rays, and the position and nature of the image formed? Normal (a) CF Incident qi qr Reflecting Object P Principal ray ray axis Reflecting surface A D Based on the image, what can be inferred? (b) P B (a) The angle between incident ray and normal is C F greater than the angle between normal and the Image at ∞ reflected ray. (b) The angle of incidence, angle of reflection, and (c) Object normal at the point of reflection do not lie on a common plane. Image C F (c) The incident ray, reflected, and normal at the point of reflection lie on a common plane. (d) Object (d) The angle between incident ray and normal is smallar than the angle between normal and the reflected ray. Ans. (b) The angle of incidence, angle of reflection, and normal at the point of reflection do not lie on a common plane. Explanation: As their plans are different but mutually perpendicular to each other. 1 17. The image shows the path of incident rays to concave mirror. Object O Image C F CF

240 CBSE Final Revision of Term-I (Class X) Ans. (a) Reflected ray Incident ray CF PF Object P Principal axis Object at infinity Convex mirror Explanation: Explanation: In concave mirror, when object is placed between P and Convex mirror is a diverging mirror, the light rays falling F, then image formed is virtual, erect and on the other on it gets diverged. side of the mirror. 120. A student studies that convex mirror always forms 1 19. Which image represents the path of incident and virtual image irrespective of its position. What causes reflected ray from a convex mirror when an object is the convex mirror to always form a virtual image? placed at infinity?  (a) Because the reflected ray never intersect. (a) Incident ray Reflected ray (b) Because the incident ray traces its path back along the principal axis Object PF at infinity (c) Because the incident ray of a convex mirror gets Convex absorbed in the mirror. mirror (d) Because the reflected ray converges at a single (b) Reflected ray point. Incident ray Ans. (a) Because the reflected ray never intersect. Explanation: Convex mirror always form virtual images because the focal point and the centre of curvature of the convex mirror are imaginary points and that connot be reached so image is formed inside the mirror and cannot be projected on the screen. PF 121. The figure given below represents the experiment carried out between conc. sulphuric acid and sodium Convex chloride, which react with each other to form HCl gas. mirror Object at infinity (c) Incident ray Reflected ray Object PF at infinity Convex mirror (d) Incident ray Reflected ray Blue litmus paper is brought near the mouth of the delivery tube to check the presence of HCl acid but Object PF no change is observed in the colour of litmus paper at infinity because Convex mirror (a) The litmus paper used is dry. (b) The litmus paper used is moist. Ans. (b) (c) Blue litmus paper does not change its colour with an acid. (d) The litmus paper is kept very close to the mouth of the delivery tube.

Science 241 Ans. (a) The litmus paper used is dry Explanation: B' Explanation: A 2F2 Litmus paper needs to be moist only if testing of a 2F1 B F1 O evolved gas is done. Water provides H+ and OH– ions F2 which help to change colour so litmus paper should be moistened before testing else in dry state it will give no A' test. 125. An object is placed near a concave mirror at a distance 1 22. Some of the uses of washing soda are given below: of one-fowth the radius of curvature of the concave (i) It is used for removing permanent hardness of mirror. Which ray diagram shows the incident rays, reflected rays, and the position and nature of the water. image formed? (ii) It is used in glass industry (iii) It is used in paper industry. (a) (iv) It is used in the manufacture of sodium compounds Object such aas borax. Select the correct option regarding uses of washing CF P Principal soda axis (a) (i) and (ii) (b) (b) (ii) and (iii) (c) (ii) and (iv) Object (d) (i), (ii) (iii) and (iv) Ans. (d) (i), (ii) (iii) and (iv) At infinity C F P Principal axis 1 23. Following observations were observed when calcium oxide reacts vigorously with water. Beaker Water Calcium oxide Identify the incorrect observations. (c) (i) It is an endothermic reaction. Object (ii) Slaked lime is produced. (iii) Quick lime is produced. C F (iv) It is a combination reaction. Image (a) (i) and (ii) (b) (iii) and (iv) (c) (i) and (iii) (d) (ii), (iv) and (v) Ans. (c) (i) and (iii) (d) Object Explanation: Image C F Calcium oxide is knowns as quick lime and reaction with water produces slaked lime as reaction is vigrous heat is released so it is an endothermic reaction. 1 24. A student conducts an experiment using a convex lens Ans. (a) of focal length 20 cm and an object of height 15 cm. He placed the object at 25 cm from the lens. Can the image be formed on a screen?[CBSE Question Banks] (a) Yes, because a real image will be formed. Object (b) Yes because an erect image will be formed. (c) No, because an inverted image will be formed. CF P Principal (d) No, because a virtual image will be formed. axis Ans. (a) Yes, because a real image will be formed.

242 CBSE Final Revision of Term-I (Class X) Explanation: (d) 'I' is the maximum for ∠i = 45º and is less than this The images formed by concave mirror is real and virtual. value for ∠i = 30º and ∠i = 60º. 126. Dispersion of light by glass prism takes place because Ans. (a) 'I' keeps on increasing with increase in angle of incidence (a) the lights of different colours have different intensities. Explanation: (b) the lights of different colours have different speed As lateral shift depends on the angles of incidence, in a medium. which increases with the increase in angle of incidence. (c) different colours have different frequencies. 129. The danger signals installed at the top of tall buildings (d) the lights of different colours have different are red in colour. These can be easily seen from a distance because among all other colours, the red energies. light.  [NCERT Exemplar] Ans. (b) the lights of different colours have different speed (a) is scattered the most by smoke on fog. in a medium. (b) is scattered the least by smoke or fog. Explanation: (c) is absorbed the most by smoke or fog. (d) moves fastest in air. White light entering the prism consists of so many Ans. (b) is scattered the least by smoke or fog. different colours. Each of these different colour has a Explanation: different wavelength. As a result the dispersion of white light takes place on the second surface of the prism. Since the red colour has the highest wavelength of all the colours and its gets scattered the lease. 127. The clear sky appears blue because 1 30. Which of the following figures correctly represents the (a) blue light gets absorbed in the atmosphere. passage of white light through prism? (b) ultraviolet radiations are absorbed in the (a) R atmosphere. V (c) violet and blue lights get scattered more than lights White light of the other colours by the atmosphere. (b) V (d) light of all other colours is scattered more than the R White light violet and blue colour lights by the atmosphere. Ans. (c) violet and blue lights get scattered more than lights of the other colours by the atmosphere. (c) Explanation: The clear sky appears blue to the Rayleigh scattering scatting of sunlight. The molecules in the air scatter blue light from the sun more than they scatter other light. 1 28. A student traces the path of a ray of light passing White light through a rectangular slab for three different values of angle of incidence (∠i) namely 30º, 45º and 60º. He extends the direction of incident ray by a dotted line and measures the perpendicular distance 'I' between (d) the extended incident ray and the emergent ray. i White light Ans. (a) R V White light l Explanation: He will observe that When white light passes through the prism it gets splits into seven colours violet colour has the least wavelength (a) 'I' keeps on increasing with increase in angle of and red colour has maximum wavelength. So violet incidence coloured light deviates the most and red colour deviates the least among the seven components colours of white (b) 'I' keeps on decreasing with increase in angle of light. incidence (c) 'I' remains the same for all three angles of incidence

Science 243 131. A student added 10g of calcium carbonate in a rigid Explanation: container, secured it tightly and started to heat it. After some time, an increase in pressure was observed, We know that when a white light beam passes through the pressure reading was then noted at intervals of 5 a prism we can observe dispersion. Hence among the mins and plotted against time, in a graph as shown four cases, given glass slab incidence only will not show below. During which time interval did maximum dispersion. decompositon took place? 1.25 1 33. A prism ABC (with BC as base) is placed in different orientations. A narrow beam of white light is incident Pressure ⎯→ 1.00 on the prism as shown in figure. In which of the following cases, after dispersion, the third from the 0.75 top corresponds to the colour of the sky? 0.50 [NCERT Exemplar] 0.25 A (a) 0 5 10 15 Time ⎯→ (a) 15-20 min (b) 10-15 min B C B (c) 5-10 min (d) 0-5 min C Ans. (d) 0-5 min (b) Explanation: For any decomposition reaction with each reactant A concentration decrease there is decrease in C concentration of product. When concentration is maximum, decomposition is also maximum and as pressure increases decomposition also decreases. 1 32. In which of the following cases will no dispersion take (c) place when sunlight passes through it? A (a) (b) C B (c) (d) A (d) Ans. (b) B B C Ans. (b) A Violet Indigo Explanation: Blue Green Yellow Orange Red

244 CBSE Final Revision of Term-I (Class X) 1 34. The graph shows the porosity and expansion of plaster Ans. (b) Atmosphere with respect to water content. Porosity of plaster in % Linear expansion of plaster 60% 0.30% 50% Expansion 0.25% Sun 40% 30% 0.20% Porosity Explanation: When sunlight reaches our atmosphere it get refracted 0.15% due to which it appears to be above the horizon than 20% 0.10% is a actually and sun rise occurs 2-minute earlier than 90 80 70 60 50 40 actual sunrise. Water : Plaster ratio 136. A student learns that the scattering of sunlight depends At what temperature, the reaction would occur? on the wavelength of the light and size of particles present in the atmosphere. The student collects the (a) 373 K data about the wavelength of the visible lights and size (b) 673 K of the particles as shown below: (c) 273 K Visible Spectrum (d) 573 K Ans. (a) 373 K 135. The sun appears two minutes before the actual sunrise due to atmospheric refraction. How does sunlight travel from space to atmosphere? [CBSE Question Bank] (a) Atmosphere 400 500 600 700 Increasing Wavelength (l) nm Which particles will scatter blue light? Sun (b) Atmosphere Particles Size (nm) P 350 Sun Q 430 R 520 S 650 (c) Atmosphere (a) Q and S (b) P and R Sun (c) P and Q (d) R and S Ans. (c) P and Q Explanation: As wavelength of blue light is about 3 nm and 500 mn. so, the particles will scatler the blue light 1 37. Two identical prism PQR and P'Q'R' are given. White light is passed through PQR as shown below: P (d) Atmosphere R V Sun White light QR Which of the following position of P'Q'R' will again yield white light?

Science 245 (a) P' (b) Q' R' (b) y d Q' R' P' O iX (c) Q' (d) R' (c) y iX R' P' P' Q' d Ans. (b) Q' O R' (d) y P' d Explanation: P O iX Ans. (a) y QR d P' When two prism are kept in inverted position than white light again. 1 38. When hydrogen sulphide gas is passed through a O i X blue solution of copper sulphate, a black precipitate of copper sulphide is obtained and the sulphuric acid Explanation: so formed remains in the solution. The reaction is an Angle of deviation in prism decreases as angle of example of: incidence increases and becomes minimum for certain (a) a combination angle of incidence and then again increases with increase in angle of incidence. (b) a displacement reaction 140. A student conducts an activity using a concave mirror (c) a decomposition reaction with focal length of 10 cm. He placed the object 15 cm from the mirror. Where is the image likely to form? (d) a double displacement reaction Ans. (d) a double displacement reaction CuSO4 + H2S → CuS + H2SO4 (blue) (black) (a) At 6 cm in front of the mirror Explanation: (b) At 6 cm behind the mirror (c) At 30 cm behind the mirror Double displacement is a reaction were the exchange of (d) At 30 cm in front of the mirror ions takes place between the two reacting compounds. Ans. (d) At 30 cm in front of the mirror Explanation: 1 39. Which of the following graph represents the correct variation of angle of incidence (i) and angle of deviation As 11 1 (d)? vu f (a) y d ⇒ 1 1  1 10 u 15 ⇒ 1 1  1 1 4 15 10 30 O iX ⇒ 4 = – 30 cm

246 CBSE Final Revision of Term-I (Class X) 1 41. The image shows the path of light travelling a glass (a) Red slab. Violet A N1 B i1 E Medium 1 Air n1 = 1 Q (b) Violet P n2 Red r1 N1' N2 Glass Medium 2 i2 (c) Red S R F r2 Lateral M N2' C Violet shift (d) d Violet ND Red What causes the ray of light to deviate from its original path? (a) Change in the temperature of the air Ans. (c) (b) Change in the amount of light (c) Change in the direction of wind flow Red (d) Change in the density of the medium Ans. (d) Change in the density of the medium Violet Explanation: The refraction occurs due to the change in density of Explanation: the medium. On to which ray of light deviates from original position. As when white light passes through a prism, it gets splitted into 7 colours and red light is deviated the least 142. Rahul conducts an experiment using an object of and violet light the most. height 10cm and a concave lens with focal length 20cm. The object is placed at a distance of 25cm from 144. Observe the given figure and answer the question that the lens. Can the image be formed on a screen? follows: (a) Yes, as the image formed will be real. (b) No, as the image formed will be inverted. (c) No, as the image formed will be virtual. (d) Yes, as the image formed will be erect. Ans. (c) No, as the image formed will be virtual. Explanation: Object Which of the following metals can be suitable for the 2F experiment? F image (i) Iron (ii) Gallium (iii) Caesium (iv) Copper 1 43. A ray of light is incident on one face of the prism, as (a) (i) and (iv) (b) (i) and (iii) shown. (c) (ii) and (iii) (d) (ii) and (iv) Ans. (a) (i) and (iv) Ray of Explanation: white light For the experiment purpose strong metals should be How will the ray of light disperse in the prism? used with good conduction of heat as heat travelled can be used to melt wax. So among all good metals are Copper and Iron are best conductors.

Science 247 145. Refer to the given figure and answer the following Metal X questions: Glass-wool Gas Y q soaked Water p with water Gas jar Burner t rs Which of these parts (i) are the actual sites of respiratory gas exchange? (a) Zinc, H2 gas (b) Copper, CO2 gas (c) Aluminium, CO2 gas (d) Platinum, H2 gas (ii) is the common passage for air and food? Ans. (a) Zinc, H2 gas (iii) is provided with incomplete cartilaginous rings? (iv) relaxes and gets back to its original shape during 148. Arrange the set-up as given below: expiration? (v) moves upwards and outwards during inspiration? (a) (i)-s, (ii)-p, (iii)-q, (iv)-r, (v)-t (b) (i)-r, (ii)-p, (iii)-q, (iv)-s, (v)-t (c) (i)-t, (ii)-q, (iii)-r, (iv)-s, (v)-p (d) (i)-p, (ii)-q, (iii)-r, (iv)-s, (v)-t Ans. (b) (i)-r, (ii)-p, (iii)-q, (iv)-s, (v)-t Explanation: Column I Column II The actual sites of gaseous exchange are alveoli which A React violently with (p) Magnesium are present in lungs represented by B. Common passage cold water for air and food is oesophagous represented by P. The ribs cage guids lungs. The diaphram plays important role B Does not react with (q) Aluminium, iron and zinc in respiration so during inhalation it bends downward cold water but and during exhalation it bends upward represented by reacts with hot S. water C Do not react with (r) Calcium water at all 1 46. There are four metals K, L, M and N. Idenfity them by using the hints given below: D Reacts less violently (s) Sodium and potassium with water and K forms basic oxide. hydrogen does not L forms amphoteric oxide. catch fire Oxide of M dissolved in water to form alkali. N does not react with water at all. E Do not react either (t) Lead copper, silver and with cold or not gold water but they react with steam (a) K → Zn, L → Al, M → Na, N → Fe (a) A-(t), B-(s), C-(q), D-(p), E-(r) (b) A-(s), B-(p), C-(t), D-(r), E-(q) (b) K → Fe, L → Na, M → K, N → Zn (c) A-(t), B-(s), C-(p), D-(r), E-(q) (d) A-(p), B-(r), C-(q), D-(s), E-(t) (c) K → K, L → Cu, M → Pb, N → Na Ans. (d) A-(p), B-(r), C-(q), D-(s), E-(t) (d) K → Cu, L → Zn, M → K, N → Pb 1 49. Figure given below is representing the dialysis machine for removing nitrogenous wastes in patient with a Ans. (d) K → Cu, L → Zn, M → K, N → Pb kidney failure. Explanation: Blood in Dialysis Fluid out K is Cu as both the oxides of copper that is Cu2O and CuO both are basic in nature as it is metal and metal Blood out oxides are generally basic in nature. N is Pb as lead Dialysi uid in do not react with water under any condition even in presence of steam do not react. M is K as oxide of potassium is K2O when dissolved in water it forms KOH which is basic in nature. 147. An experimental set-up is shown in the figure. Identify the metal (X) and gas (Y) respectively in the figure.

248 CBSE Final Revision of Term-I (Class X) Which substances out of the following in the dialysis What is the appearance of lime warter in flasks 1 and 2 fluid should be at a lower concentration than in the after a period of ten minutes? blood of patient? S.No. Flask 1 Flask 2 (a) Glucose and urea (b) Glucose and amino acids (a) Clear Clear (b) Clear White/Cloudy (c) Salts and urea (d) Glucose and salts (c) White/Cloudy Clear (d) White/Cloudy White/Clludy Ans. (c) Salts and urea Explanation: The dialysis fluid contains no urea, so all urea diffuses Ans. (b) Clear, White/Cloudy from blood to dialysis fluid from higher concentration of blood to lower concentration of dialysis fluid. Explanation: Concentration of salts are high in blood but kept low in dialyser and are regularly removed from blood. Since flask 1 is connected to main flask that contains solution to absorb CO2. Hence reactions between CO2 1 50. Clean small pieces of magnesium, zinc, aluminium, and lime water do not take place, while in flask B no iron and copper by rubbing them with a piece of sand such solution is present so CO2 reacts with lime water paper. Take them in separate test tubes. Add about to form white precipitate of CaCO3. 10mL of dilute hydrochloric acid to each of them. 152. In each test tubes A, B, C and D, 2ml. of solution of Al2(SO4)3 in water was filled. Clean pieces of zinc was placed in test tube A, clean iron nail was put in test tube B, silver (Ag) was placed in test tube C and a clean copper wire was placed in test tube D. Identify the correct statement(s). (i) The rate of evolution of hydrogen gas bubbles is not same in all the test tubes. (ii) The rate of formation of bubbles is the fastest in the case of magnesium. (iii) The reactivity decreases in the order: Mg > Zn > Al > Fe > Cu Al (SO ) + Zn Al (SO ) + Fe Al (SO ) + Ag Al (SO ) + Cu 2 43 2 43 2 43 2 43 (iv) In the case of copper, no bubbles are seen and the (A) (B) (C) (D) temperature also remains unchanged. This shows that copper does not react with dilute HCl. Which of the following option(s) is/are correct about above experiment? (a) (ii) and (iv) (b) (iii) and (iv) (a) Zinc is more reactive than aluminium (c) Only (iii) (d) (i), (ii) and (iv) (b) Copper is more reactive than aluminium (c) Zinc is more reactive than copper Ans. (d) (i), (ii) and (iv) (d) Zinc, iron, silver and copper are less reactive than Explanation: aluminium. Evolution of hydrogen gas with reaction of acid and Ans. (d) Zinc, iron, silver and copper are less reactive than metal depends on reactivity of metal. As the reactivity aluminium. of metal increases rate of evolution of gas also increases Mg is at top most in reaction series. Hence rate is Explanation: maximum for magnesium. Zn, Fe, Ag and Cu are less reactive than aluminium. 151. An experiment is set up as shown. Flasks 1 and 2 Aluminium resides at the top of the activity series. While contain lime water. Air is pumped through the flasks. Zn, Fe, Ag and Cu lies below aluminium in the activity series. Thus, being less reactive than aluminium, they cannot displace Al from its salt solution i.e., Al2(SO4)3 solution. 153. In an experiment each of the metals Al, Zn, Cu and Fe are reacted with ZnSO4, CuSO4, Al2(SO4)3 and FeSO4 solutions. The results are tabulated as follows where (√) means that the reaction occurs and (X) means no reaction occurs.

Science 249 Metal ZnSO4 CuSO4 Al2(SO4)3 FeSO4 Explanation: Zn     Cu     Iron is less reactive than aluminium, it cannot displace Al     aluminium from aluminium sulphate solution. So colour Fe     of the solution does not change. Iron is more reactive than copper, it displaces copper from copper sulphate solution. So, blue colour of the solution changes to green. On the basis of the above results, the order of the 1 56. The diagram shows a vertical section through the reactivity of the metals may be concluded as: heart. (a) Zn > Fe > Al > Cu (b) Al > Fe > Zn > Cu 1 (c) Zn > Al > Fe > Cu (d) Al > Zn > Fe > Cu Ans. (d) Al > Zn > Fe > Cu 3 154. A plant is kept in the dark for two days. A leaf is used in 2 an experiment to investigate the effect of two factors 4 on photosynthesis as shown in the diagram. Left ventricle What are the functions of the numbered blood vessels? Carries Carries Carries Carries blood to What are the colours of Q and R, when the leaf is S. No. blood to blood from blood from tested for starch, using iodine solution? body lungs lungs body S.No. Q R (a) 1 2 3 4 (b) 1 3 4 2 (a) Blue/Black Brown (c) 2 4 3 1 (b) Brown Brown (d) 3 1 4 2 (c) Blue/black Blue/black (d) Brown Blue/black Ans. (b) Q-Brown, R-Brown. Ans. (d) 3, 1, 4, 2 Explanation: 1 55. Aluminium sulphate and copper sulphate solutions were taken in two test tubes I and II, respectively. A Vessel 1 is pulmonary artery and carries blood to lungs few pieces of iron filings were then added to both the Vessel 2 is vena cava and carries blood from body to solutions. Four students A, B, C and D recorded their observations in the form of a table as given below: heart. Vessel 3 is aorta and carries blood from heart to body. Students Aluminium sulphate Copper sulphate Vessel 4 is pulmonary vein and carries blood from lungs solution (I) solution (II) to heart. Blue colour of the A Colourless solution solution is retained 1 57. Aqua regia, (Latin for 'royal water') is a freshly prepared changes to light green mixture of concentrated.....(i).....and.....(ii).....in the ratio Blue colour of the of 3 : 1. It can dissolve.......(iii)......, even though neither Colour of the solution solution changes to of these acids can do so alone. Aqua regia is a highly B does not change green corrosive, fuming liquid. It is one of the few reagents that is able to dissolve......(iii).....and ......(iv)..... . Colourless solution Blue colour of the C changes to light blue solution changes to green (i) (ii) (iii) (iv) Blue colour of the D Colour of the solution solution fades away (a) Conc. HCl Conc. HNO3 Gold Platinum remains unchanged Conc. HCl Gold Platinum (b) Conc. HNO3 Conc. HNO3 Silver Gold The correct set of observations has been recorded by (c) Conc. H2SO4 Conc. HCl Gold Platinum student: (d) Conc. H2SO4 Conc. HNO3 Gold Platinum Ans. (a) Conc. HCl (a) A (b) B (c) C (d) D Ans. (b) B