202110188-APEX-STUDENT-WORKBOOK-SCIENCE-G07-PART2

17. CHANGES AROUND US SESSION 1 INTRODUCTION 1.1 Terminology i. Periodical changes – The changes which repeat after some period of time are known as periodical changes. ii. Periodical events – The events which repeat at regular intervals of time are called Periodical Events. 1.2 Key Concepts i. We notice several changes that occur around us. ii. Some of them are temporary, some of them are permanent. iii. Some of the changes take place very quickly and some slowly. iv. Some changes repeat after some period of time. Such changes are known as periodic changes. v. The events which repeat at regular intervals of time are called periodic events. SESSION 1. INTRODUCTION 99

SESSION 2 PHYSICAL CHANGES 2.1 Mind Map 2.2 Terminology i. Physical change – A physical change is a change in which no new substances are formed. ii. Solidification –Solidification is a phase in which a liquid turns into a solid when its tempe- rature is lowered below its freezing point. 2.3 Key Concepts i. Change where no new substances is formed is known as physical change. ii. When a material undergoes a change in shape, size, colour or state it is called a physical change. iii. In our day to day life we observe many physical changes. SESSION 2. PHYSICAL CHANGES 100

2.4 Conceptual Understanding Q1. Fill in the blanks in the following statements: [Refer to TB page 167 Q9](b)) Changes in which only properties of a substances changes are called physical changes. A. Changes in which only physical properties of a substances changes are called physical changes. Q2. Answer the following questions: [Refer to TB page 167 Q10](III), (IV), (V)) 1. A piece of paper was cut into four pieces. What type of change occurred in the property of paper? (a) Physical change (b) Chemical change (c) Both changes (d) No change 2. Aryan stretched a rubber band. What does it represent? (a) Chemical Change (b) Physical Change (c) Both changes (d) No change 3. Which of the following changes are reversible or irreversible? (a) Rise of water from ground to the over head tank? (b) Setting of cement (c) Absorption of water by a sponge. (d) Migration of birds. (e) Rise in temperature during summer. A. 1. (a) Physical change: The paper has become small when it was cut into pieces that is it has under gone a change in size. SESSION 2. PHYSICAL CHANGES 101

2. (b) Physical Change: The rubber band has attained increase in length. If we remove our force it will regain its normal size. So it is a temporary change. 3. a) Rise of water from ground to the over head tank is reversible. If we switch of the motor and open the tap head the water flows down to the ground again. b) This change is irreversible when once water is added to set cement, the cement un- dergoes certain changes with atmospheric air and so new substances form. c) This change is reversible. If we squeeze the sponge all the water will come out. d) This is reversible change. When the conditions of climate change in the native country the birds go back to their natural habitat. e) This is reversible. When the summer season comes to an end and rains set in, the temperatures would come to their original, level. SESSION 2. PHYSICAL CHANGES 102

SESSION 3 CHEMICAL CHANGES 3.1 Mind Map 3.2 Terminology i. Chemical change – Chemical change is any change that results in the formation of new chemical substances. ii. Galvanisation –It is the process of applying a protective zinc coating to steel or iron, to prevent rusting. iii. Crystallization – The process of separating a soluble solid from the solution on heating is called Crystallization. iv. Rusting –Rusting is the common term for corrosion of iron and its alloys, such as steel. v. Lime water – Limewater is the common name for a diluted solution of calcium hydrox- ide. vi. Baking soda –Chemical name –sodium bicarbonate. It is a chemical compound used in cooking, for cleaning, or in toothpaste. SESSION 3. CHEMICAL CHANGES 103

vii. Vinegar – A sour–tasting liquid containing acetic acid, obtained by fermenting dilute alcoholic liquids. viii. Rust – A reddish–or yellowish–brown flaking coating of iron oxide that is formed on iron or steel by oxidation, especially in the presence of moisture. 3.3 Key Concepts i. When a material undergoes change in its composition, it is called chemical change. ii. In chemical change, one or more new substances are formed. iii. A chemical change is also called as a chemical reaction. iv. In any change, heat, light, radiation or sounds may be produced. v. In a change, a new colour or smell may appear. vi. Process of depositing one metal on another metal is called galvanisation. vii. Zinc is generally used in the process of galvanisation. viii. The process of separating a soluble solid from the solution by heating or evaporating is called crystallization. ix. A brown layer on the surface of the iron particles is called “rust” and the process by which this layer is formed is called rusting. 3.4 Conceptual Understanding Q1. Why do we paint wooden doors and windows? [Refer to TB page 166 Q1] A. • We paint wooden doors and windows to prevent wear and tear of wood. • Wooden articles slowly undergo combustion with atmospheric oxygen and lose strength. • Slowly they are worn out and may break. • So wooden doors and windows are painted to obstruct their contact with oxygen in the air. Q2. Some deposits were observed in water preserved in aluminium containers after two to three days. What could the deposit be? What is the reason for the formation of these deposits? [Refer to TB page 166 Q2] SESSION 3. CHEMICAL CHANGES 104

A. • When water is preserved in an aluminium container for 2 to 3 days, we observe some deposits. • When aluminium reacts with air enclosed in the container, the oxygen of air under- goes a chemical change with aluminium, forming oxide of aluminium. • This aluminium oxide reacts with water to form aluminium hydroxide a white sub- stance is formed. • The formation of deposit on water is due to quick appearance of this aluminium compound. Q3. How is an iron gate prevented from rusting? [Refer to TB page 167 Q4] A. To prevent iron gate from rusting we should avoid its contact with oxygen or water. • A simple way is to apply a coat of paint or grease on the gate. • Another way is to deposit a layer of a metal such as zinc or chromium on the iron gate. This process is known as galvanization. Q4. Between coastal and dry land areas, where is rusting of iron objects faster? Give rea- sons. [Refer to TB page 167 Q5] A. Between coastal and dry land areas, rusting of iron takes place quickly in coastal areas. Reasons: • For rusting of iron, both the presence of oxygen and water vapour is essential. • In dry lands, the humidity of air is less. • In coastal areas, the humidity is high because sun’s rays evaporate water and this water vapour accumulates in the atmosphere. Q5. Fill in the blanks with the following statements: [Refer to TB page 167 Q9](a)) The chemical name of vinegar is . A. The chemical name of vinegar is acetic acid. Q6. When you burn a piece of wood, different changes take place. Analyze the following: [Refer to TB page 168 Q18] (a) Predict possible changes and list them all. SESSION 3. CHEMICAL CHANGES 105

(b) Are there any physical changes among them? (c) How many forms of energy are released in the change? (d) What chemical changes do you notice? Explain briefly why these occur. A. (a) When we burn a piece of wood, at first we see a flame, then after the wood is burnt completely, we notice ash is formed. We find that a gas which turns limewater milky is also released in this experiment along with a little water vapour. (b) Yes, there are physical changes in these activities. (c) Energy in the form of (i) heat, (ii) light and (iii) chemical energies is released in this process. (d)The following chemical changes take place. • The carbon in the wood reacts with the the atmospheric oxygen and releases CO2 . • Some of the carbon compounds are left behind in the form of ash. • A little water vapour is formed in this process. These changes takes place because carbon and oxygen of air combine to form CO2 and H2 present in the wood react with this oxygen to form water vapour. Q7. Which of the following process are chemical changes Give reasons. [Refer to TB page 167 Q7] (a) Making a salt solution (b) Adding hydrochloric acid to marble stone (c) Evaporation of water (d) Adding phenolphthalein indicator to acid solution (e) Respiration (f) Ripening of a mango (g) Breaking of glass SESSION 3. CHEMICAL CHANGES 106

A. (a) Making a salt solution It is a physical change. Reasons: 1) No new substance is formed. 2) Water and salt can be separated by evaporation, a simple mechanical process. (b) Adding hydrochloric acid to marble stone Adding hydrochloric acid to marble stone is a chemical change. Reason : Marble stone reacts with hydrochloric acid forming calcium chloride and carbon dioxide. New substances are formed. Calcium carbonate (Marble stone) + Hydrochloric acid —>Calcium chloride + water + carbon dioxide (c) Evaporation of water Evaporation of water is a physical change. It is a temporary change. Reason: Water can be formed back by cooling the water vapours. (d) Adding phenolphthalein indicator to acid solution It is a physical change. Reason: No change occurs. (e) Respiration Respiration is a chemical change. Reason: The oxygen respired, in order to be transported, mixes with the blood by a chemical reaction. A chemical reaction takes place. Energy in the form of heat is released which is used in doing our daily work. New substances formed such as carbon dioxide and uric acid are carried by blood to the excretory organs. SESSION 3. CHEMICAL CHANGES 107

(f) Ripening of a mango Ripening of a mango is a chemical change Reason: The sour mango becomes sweet due to the change in the components. (g) Breaking of glass Breaking of glass is a physical change. Reason: It changes the shape, and size of the glass. No new substance is formed. No energy in any form is released. Q8. Identify the incorrect statements among the following and write them correctly. [Refer to TB page 167 Q8] a) Formation of manure from leaves is a physical change. b) Iron pipes coated with zinc are not rusted. c) Setting of curd is physical change. d) Condensation of steam is not a chemical change. e) Burning of magnesium in air is a chemical change. A. a) Formation of manure from leaves is a physical change. Incorrect: Formation of manure from leaves is a chemical change. The leaves are de- graded and decomposed by various bacteria into various nitrogenous compounds. New substances are formed and hence it is a chemical change. b) Iron pipes coated with zinc are not rusted. Correct C) Setting of curd is physical change. Incorrect: Setting of curd is a chemical change affected by lactic acid bacteria and we cannot get back milk from curd by simple mechanical process. SESSION 3. CHEMICAL CHANGES 108

d) Condensation of steam is not a chemical change. Correct e) Burning of magnesium in air is a chemical change. Correct Q9. Answer the following questions. [Refer to TB page 167 Q10](I), (II)) 1. The gas we use in kitchen is in the form of liquid in the cylinder. When it comes out from the cylinder it becomes a gas (step I), then it burns (step II). Choose the correct statement from the following: (a) Only step I is a chemical change. (b) Only step II is a chemical change. (c) Both steps I and II are chemical changes. (d) Both steps I and II are physical changes. 2. Bacteria digest animal waste and produce biogas (Step I). The biogas is then burnt as fuel (Step II). Choose the correct statement from the following: (a) Only step I is a chemical change. (b) Only step II is a chemical change. (c) Both steps I and II are chemical changes. (d) Both steps I and II are physical changes. A. 1. (b) Only step II is a chemical change. 2. (c) Both steps I and II are chemical changes. Q10. Fill in the blanks in the following statements: [Refer to TB page 167 Q9](c), (d), (e)) i. Changes in which new substances are formed are called changes. SESSION 3. CHEMICAL CHANGES 109

ii. Magnesium + oxygen –––––––> . iii. Copper sulphate + iron ––––––––> . A. 1. Changes in which new substances are formed are called chemical changes. 2. Magnesium + oxygen ——– > Magnesium oxide. 3. Copper sulphate + iron –––––––> Ferrous sulphate. Q11. When a candle is burnt, what type of changes take place? Give another example of a similar process. [Refer to TB page 167 Q3] A. i. When a candle is burnt in air, wax is burnt and it gets converted into vapour. ii. It is both a physical and a chemical change. iii. Burning of wood is also similarly both a physical and a chemical change. 3.5 Information Skills and Projects Q1. Collect information on changes taking place in food during the process of digestion; when we eat raw and cooked food, from the school library/ internet and display your observations on the bulletin board. [Refer to TB page 168 Q15] A. Students’ activity. When we eat cooked food: a) The carbohydrates changes into glucose and fructose and these substances are dissolved in blood. b) The proteins change into peptones and peptides and join the blood. c) The fats are converted into “Amino Acids” and form an emulsion. In this way all the nutrients undergo change from an insoluble state to a soluble state. Q2. Collect information on the process of artificial ripening of fruits in fruit markets and dis- cuss whether it is useful or harmful. [Refer to TB page 168 Q16] A. 1. In recent times, there is much concern about artificial ripening of fruits. Though fruits like mango naturally ripen in trees; some chemicals are used to ripen them artificially which accelerate the ripening process. 2. Ripening is a process in fruits that causes them to become edible. SESSION 3. CHEMICAL CHANGES 110

3. For many years, ethylene had been used as a fruit ripening agent, but nowadays ethane, calcium carbide and ethephon are commonly used for faster ripening. But inap- propriate use of these chemicals to ripen fruits is associated with many health hazards. 4. Ill–effects of artificial ripening i. Ethylene is known to cause damage to the neurological system, affects the eyes, skin, lungs, memory and leads to prolonged hypoxia (lack of oxygen supply). ii. Ethephon is a plant growth regulator. It promotes pre–harvest ripening in apples, blueberries, figs, tomatoes, capsicum etc. Ethephon is easily converted into ethy- lene and has the same harmful effects. iii. State Food and Drugs Control Administration (FDCA) has banned the use of ethep- hon last year, but fruit traders have now resorted to bethylene. iv. Bethylene is not known to have any harmful effects but it alters the taste and the nutritional value of fruits and also reduces the shelf life of the fruits, if used beyond the recommended limits. And most of the traders do use quantities of bethylene which are much higher than the prescribed limits. 3.6 Communication Through Drawing and Model Making Q1. Ravi prepared carbon dioxide using baking soda and vinegar. Carbon dioxide changed limewater milky. Represent the experiment in a diagram with labeling. [Refer to TB page 168 Q17] A. Students’ activity. SESSION 3. CHEMICAL CHANGES 111

Parts: 1. Baking Soda and Vinegar 2. Lime water 3. Glass flask 4. Delivery tube 5. Stand 3.7 Appreciation and Aesthetic Sense, Values Q1. Anurag appreciates the change in ripe mango as ‘How nice its color and taste is Give some examples of change that make you feel happy or wonder or appreciate them in your own words. [Refer to TB page 168 Q12] A. 1. When wet turmeric paste sticks to my white shirt, my shirt turns yellow at the spot. 2. But when I apply washing soap, the yellow spot changes to red color, I wonder at this color change. 3. When methyl orange (an indicators) which has orange color is added to an acid, it turns to red color. I appreciate this change of color. 4. When we white wash the walls of our house, the dull color less limewater (calcium hydroxide) gradually changes to bright white color. This is because limewater absorbs SESSION 3. CHEMICAL CHANGES 112

carbon dioxide from air and changes to calcium carbonate, which is white in color. I appreciate this color change because the pale walls of my house turn bright white. Q2. The changes like, chicks came out of eggs, blossoming flowers are very pretty to see. List out such type of changes around you which make to feel happy on observing the beauty of change. [Refer to TB page 168 Q13] A. Students’ activity. Can make use of below examples. Ripening of fruits, Evaporation of water, Germination of seeds, Sunrise and Sun- set, Formation of rainbow. The other changes, which make me feel happy on observing the beauty of nature, are 1. The caterpillar which causes irritation when it crawls on our skin, after sleeping for a few days breaks out of the cocoon and comes out with varied colors in the form of a butterfly. I feel happy when I see a butterfly in my school garden. 2. When it rains, the drops of rain may still be suspended in the atmosphere. Just then when the sun peeps through the clouds with the sunlight, there appears a wonderful rainbow with all its splendid seven colors. How can I suppress my joy on seeing the colorful rainbow! 3. The egg of a bird is white in color. However, when it hatches and grows into a pigeon of blue color, I appreciate nature’s actions. 3.8 Application to Daily Life, Concern to Bio Diversity Q1. Sudheer wants to make his vessels which are made of brass and copper, clean and shiny. What suggestions would you like to give him? [Refer to TB page 168 Q11] A. i. Sudheer wants to make his vessels made of brass and copper clean and shiny. ii. Brass and copper vessels undergo chemical change with the oxygen in air. Green seals of copper compounds are formed on the vessels. iii. As this is a chemical change and a permanent change. We cannot make them clean and shiny. iv. As the copper salts undergo chemical change with acids, we can clean the ves- sels with tamarind. Tamarind contains tartaric acid and due to chemical reaction between the green seals and tartaric acid, they are removed by the tartaric acid and the vessels regain their brightness. SESSION 3. CHEMICAL CHANGES 113

SESSION 4 IDENTIFYING PHYSICAL AND CHEMICAL CHANGES 4.1 Mind Map 4.2 Terminology i. Turmeric – A bright yellow aromatic powder obtained from the rhizome of a plant of the ginger family, used for flavouring and colouring in Asian cookery. SESSION 4. IDENTIFYING PHYSICAL AND CHEMICAL CHANGES 114

ii. Calcium hydroxide – It is a colorless crystal or white powder and is obtained when calcium oxide is mixed with water. 4.3 Key Concepts i. Changes mainly are of two types: physical and chemical. ii. When a material undergoes a change in shape, size, colour or state without a new substance getting formed, then it is called a physical change. iii. In a physical change generally no new substance is formed. iv. When a material undergoes a change in its composition, it is called a chemical change. v. In a chemical change new substance is formed. 4.4 Conceptual Understanding Q1. Classify the change involved in the following process as physical, chemical or both. [Refer to TB page 167 Q6] i. Burning of coal ii. Melting of wax iii. Beating aluminum to make aluminum foil iv. Digesting food v. Boiling of egg vi. Photosynthesis vii.Cutting of wood A. i. Burning of coal –Chemical ii. Melting of wax –Physical iii. Beating aluminum to make aluminum foil –Physical iv. Digesting food – Chemical v. Boiling of egg – Chemical vi. Photosynthesis –Chemical vii. Cutting of wood –Physical SESSION 4. IDENTIFYING PHYSICAL AND CHEMICAL CHANGES 115

Q2. Match the following: [Refer to TB page 168 Q14] A. 4.5 Information Skills and Projects Q1. Collect information on the process of artificial ripening fruits in fruit markets and discuss whether it is useful or harmful. [Refer to TB page 168 Q16] A. 1. Now a day’s people are eager to get ripe fruits as early as possible. 2. The fruit sellers are also crazy to make high profits by releasing ripe fruits into the markets as early as possible. 3. So, in the fruit market the sellers are adopting artificial methods of ripening fruits. 4. For example: (I) A gas called ‘Acetylene’ is used in artificial ripening of fruits. (ii) A chemical called “Calcium carbide” is used in brining quick ripening of mangoes. 5. But these methods are harmful to our bodies. 6. The chemicals they use in artificial ripening of fruits cause illness in the end. SESSION 4. IDENTIFYING PHYSICAL AND CHEMICAL CHANGES 116

—— CCE Based Practice Questions —— AS1-Conceptual Understanding Very Short Answer Type Questions 1. Match the cases with respect to its change: [(Session 17.2)] Column A Column B i. Burning of crackers a. Change in size and shape ii. Drying of wet coconut b. Change in state from solid to liquid iii. Heating of coloured candle c. Change in state from liquid to solid iv. Melting of gold ornaments d. Formation of new substance v. Filling air into balloons e. Change in size and state 2. Match the following. Column B [(Session 17.3)] a. Galvanisation Column A i. Rusting of iron ii. Depositing one metal on another b. Crystallization iii. Ascorbic acid c. Corrosion iv. Separating soluble solids from solution d. Rust v. Moist iron oxide e. Prevent browning 3. Fill in the blanks. [Refer to Session 17.3 ] (i) A greenish coat formed on the copper utensils protects copper from being further . (ii) The process of depositing zinc over iron or steel is called . CHAPTER 17. CHANGES AROUND US 117

(iii) prevents the outer surface of vegetables from colouring. (iv) Magnesium + Oxygen → . (v) Carbon dioxide + Limewater → + Water. 4. Match the following. [(Session 17.1)] Column A Column B i. Change that takes place once every a. Natural change year ii. Fast change b. Melting of gold iii. Change that takes place once every c. Withering of leaves fortnight iv. Formation of rust on iron bars d. Appearance of full moon v. Change that we initiate e. Burning of paper Short Answer Type Questions 5. Answer the following questions in 3-4 sentences. (i) [(Session 17.2)] What do you mean by a physical change? (ii) [(Session 17.2)] What happens when ice is heated? What happens when water vapour is cooled? 6. Answer the following questions in 3-4 sentences. (i) [(Session 17.3)] What do you mean by rusting? (ii) [(Session 17.3)] What do you mean by galvanization? Long Answer Type Questions 7. Answer the following questions in 6-8 sentences. (i) [(Session 17.2)] What happens during a physical change? Give examples of some physical changes. CHAPTER 17. CHANGES AROUND US 118

8. Answer the following questions in 6-8 sentences. (i) [(Session 17.1)] Define the term ‘change’. What are the types of changes? AS3-Experimentation and field investigation Long Answer Type Questions 9. Answer the following questions in 6-8 sentences. (i) [(Session 17.3)] What do you mean by crystallization? Briefly, describe the procedure of crystallization of sugar. AS4-Information skills and projects Long Answer Type Questions 10. Answer the following questions in 6-8 sentences. (i) [(Session 17.4)] Prepare a report on changes taking place during growth in human. (You can take the help of your teachers and elders) AS5-Communication through drawing and model making Short Answer Type Questions 11. Answer the following questions in 3-4 sentences. (i) [(Session 17.2)] With the help of a diagram define a physical change. Long Answer Type Questions 12. Answer the following questions in 6-8 sentences. (i) [(Session 17.1)] Draw a flowchart representing types of changes around us. AS6-Appreciation and aesthetic sense, Values Long Answer Type Questions 13. Answer the following questions in 6-8 sentences. (i) [(Session 17.4)] Which one do you agree: “Chemical changes are beneficial/harmful for us”? Justify your answer. CHAPTER 17. CHANGES AROUND US 119

AS7-Application to daily life, concern to bio diversity Long Answer Type Questions 14. Answer the following questions in 6-8 sentences. (i) [(Session 17.4)] List out some of the physical and chemical changes taking place in our daily life. Objective Questions AS1-Conceptual Understanding 15. Choose the correct answer. (i) An example of physical change: (A) Melting of ice (B) Formation of curd (C) Digestion (D)Spoilage of food (ii) Change of day and night is an example of (A) physical change (B) periodical change (C)chemical change (D)biological change (iii) In which cases are new substances formed? (A) Change of milk into curd (B) Cutting piece of wood (C)Drying of clothes (D)Melting of gold (iv) During a change, when a new substance is formed it is called as change. (A) physical (B) chemical (C) periodic (D) none (v) Rusting is a change. (A) physical (B) chemical CHAPTER 17. CHANGES AROUND US 120

(C) periodic (D) biological (vi) What do you call the process of depositing zinc metal on iron? (A) Rusting (B) Galvanisation (C) Painting (D) Crystallisation (vii) Which of the following is not a chemical change? (A) Burning of camphor (B) Crystallisation of sugar (C)Ripening of fruits (D)Preparation of tea (viii) Condensation of steam is a change. (A) physical (B) chemical (C) spontaneous (D) none (ix) Bacteria digest animal waste and produce (A) Biogas (B) Carbon dioxide (C) Urea (D) Nitrogen (x) Galvanisation: (A) Prevents rusting (B) Leads to corrosion (C)Prevents oxidation (D)All of the above CHAPTER 17. CHANGES AROUND US 121

PROJECT BASED QUESTIONS —— Project Based Questions —— (i) Discuss with your friends and parents and make a list of items in your daily life where you find the application of plane mirror and spherical (convex and concave) mirrors. (ii) Search from the internet and name the medicinally important insectivorous plant found in Andhra Pradesh. Insectivorous plants are also called carnivorous and het- erotrophic. Explain why? Also write a note on the insect–trapping mechanism in any insectivorous plant. (iii) Collect at least five different flowers from your surroundings and observe their various parts. Record your observations in the table given below: (iv) Conduct an experiment of seed dispersal. In this experiment, you will have to make models of seeds and fruit to investigate dispersal of seeds by wind and to evaluate the relationship between the structure of the seed and its ability to be dispersed by the wind. Project Based Questions 122

Additional AS- Based Practice Questions Chapter 9: Reflection of Light Q1. Here are given capital letters of English alphabet encircle the alphabet which will not show lateral inversion on facing a plane mirror. (AS4) Q2. Mohit argues that placing a mirror near lights, and table lamps reflects the light over a larger area, and makes the room appear brighter. Is he right? Support your answer. (AS2) Q3. Images in a mirror are located at the same distance behind the mirror as the object in front of it. Explain the importance of this property of mirror. (AS6) Q4. Which property of light can be appreciated for occurrence of rainbow? (AS6) Q5. Draw diagram showing spherical mirrors. (AS5) Chapter 10: Nutrition in Plants Q1. A goat eats away all the leaves of a small plant (balsam). However, in a few days, new leaves could be seen sprouting in the plant again. How did the plant survive without leaves? Provide suitable hypothesis to it. (AS2) Q2. How humans and animals are directly or indirectly dependent on plants? (AS6) Q3. Appreciate the role of plants of Dal family in replenishing soil fertility? (AS6) Q4. Show with the help of sketch that plants are the ultimate source of food? (AS5) Q5. How would you test the presence of starch in leaves? (AS3) Q6. Read the paragraph below and answer the following questions. (AS4) “Only certain part plant like leaves having green pigment chlorophyll. So, leaves are called the food factories of plants. Besides leaves, photosynthesis also takes place in other green parts of the plant — in green stems and green branches. The desert plants have scale- or spine-like leaves to reduce loss of water by transpiration. These plants have green stems which carry out photosynthesis.” Additional AS-Based Practice Questions 123

i. Name the plant part mainly responsible for making food. ii. Whether food is made in all part of plants or only certain parts? iii. What is transpiration? Q7. How would you prove the essentiality of green colour pigment chlorophyll for photosynthesis by an experiment? (AS3) Q8. How are saprophytes beneficial to environment? (AS7) Chapter 11 – Respiration in Organisms Q1. Take 3 test tubes. Fill 3/4th of each with water. Label them as A, B and C. Keep a snail in test-tube A, a water plant in test-tube B, keep snail and plant both in test-tube C. Which test-tube will have highest concentration of carbon dioxide. (AS3) Q2. Why does a person’s rate of breathing increases during heavy exercise? (AS2) Q3. How do you appreciate the work of Von Helmont and Joseph black on discovery of carbon dioxide? (AS6) Q4. Spiracles are the small holes on the cockroach which helps in breathing. Collect more information about the spiracles. (AS4) Q5. Observe the table below. Gases Inhaled air (ml) Exhaled air (ml) Oxygen 210 165 Carbon dioxide 0.4 40 Quantity of oxygen inhaled is more than that of exhaled whereas exhaled quantity of CO2 is more than inhaled. Why do you think is the difference the two. (AS2) Q6. Draw a labelled diagram of human respiratory system showing inhalation and exhalation. (AS5) Q7. During emergency conditions artificial respiration is provided in hospital. Why does a person need artificial respiration? (AS7) Chapter 12 – Reproduction in Plants Q1. Sketch a flow chart of sexual reproduction taking place in a flower. (AS5) Q2. Observe and complete the following table. (AS4) Additional AS-Based Practice Questions 124

Vegetative reproduction Examples of plants (Parts of the plants involved) New plants grows from the modified root. New plants grow from eyes in the tuber which is a modified stem. New plants grows from bulbs or corms which are modified stems. New plants grows from the buds on the leaf. Stem grows roots at the nodes. Stem creeps along the ground and strikes roots at the nodes. Q3. Devise an experiment to know the significant role played by male flower in the formation of fruit. (AS3) Q4. You have many questions to ask on process of fertilisation. Prepare a list of questions to ask your teacher. (AS2) Q5. Why reproduction is essential life process? (AS7) Q6. Show self-pollination and cross-pollination through a labelled diagram. (AS5) Chapter 13 – Seed Dispersal Q1. Group the seeds given below according to their mode of dispersion. (AS5) a. b. c. d. Additional AS-Based Practice Questions 125

e. Q2. Coconut is a large and heavy fruit. How do you think it is adapted for dispersal of water? (AS2) Q3. Appreciate the work of birds and animals as a mode of dispersion. (AS6) Q4. Collect different types of locally available seeds and try to analyse the size, shape or nature of seeds. (AS3 or AS4) Q5. Dispersal by bursting of fruits is an entirely different mechanism compared to other modes. Write your comments on this. (AS6) Q6. Rajesh said “Dried seeds can germinate and grow into a new plant”. Is he correct? Why do you think so? (AS7) Chapter 17 – Changes Around Us Q1. You would have seen melting of wax/ice where solid changes to liquid. Give similar example where liquid changes to solid. (AS7) Q2. Photosynthesis is a types of change taking place in a plant. Collect information on the changes which takes place during the process. (AS4) Q3. List the methods to overcome/prevent rusting of iron. (AS7) Q4. Uma said “Crystallization is a better technique to obtain sugar from sugar solution than evaporation”. Prepare a list of questions to know why she has thought this. (AS2) Q5. Devise an experiment to observe the changes when burning materials. (AS3) Q6. Draw a picture which shows the physical change or chemical change. (AS5) Additional AS-Based Practice Questions 126