202110243-TRIUMPH-STUDENT-WORKBOOK-PHYSICAL_SCIENCE-G09-PART1

(iii) [(Session 6.3)] Classify the following as element or compound. a) Oxygen b) Copper c) Water d) Iron e) Salt f) Methane 7. Answer the following questions in 3-4 sentences. (i) [(Session 6.1)] Define homogeneous and heterogeneous mixture. (ii) [(Session 6.1)] Distinguish between dispersed phase and dispersion medium. (iii) [(Session 6.1)] Write the dispersed phase and dispersion medium for: a) Clouds b) Milk c) Cheese CHAPTER 6. IS MATTER PURE? 199

Long Answer Type Questions 8. Answer the following questions in 6-8 sentences. (i) [(Session 6.2)] Describe the following separation techniques. Give one example for each. a. Sublimation b. Evaporation c. Chromatography d. Distillation e. Fractional Distillation CHAPTER 6. IS MATTER PURE? 200

CHAPTER 6. IS MATTER PURE? 201

9. Answer the following questions in 6-8 sentences. (i) [(Session 6.1)] Tyndall effect can be observed when sunlight passes through the canopy of a dense forest. Why do you think this phenomenon happens? CHAPTER 6. IS MATTER PURE? 202

AS2-Asking questions and making hypothesis Short Answer Type Questions 10. Answer the following questions in 3-4 sentences. (i) [(Session 6.2)] What kind of mixtures can be separated using sublimation? AS3-Experimentation and field investigation Short Answer Type Questions 11. Answer the following questions in 3-4 sentences. (i) [(Session 6.2)] How would you separate different colours in a pigment? CHAPTER 6. IS MATTER PURE? 203

12. Answer the following questions in 3-4 sentences. (i) [(Session 6.1)] Iron fillings mixed with sulphur powder can be separated using a mag- net. But the same Iron fillings when heated with sulphur does not show magnetic property. What is the reason behind the two different observations. Long Answer Type Questions 13. Answer the following questions in 6-8 sentences. (i) [(Session 6.2)] You have been given a mixture that contains: water, ethanol, coconut oil, and salt. You are asked to separate out each of these substances. Write the processes that would need to be performed in order to separate all of these, and also write the order in which these have to be performed. CHAPTER 6. IS MATTER PURE? 204

AS4-Information skills and projects Very Short Answer Type Questions 14. Answer the following questions in one sentence. [Refer to Session 6.3 ] (i) Complete the table. Mixtures Homogeneous/Heterogeneous Soda water Homogeneous Wood Air Homogeneous Soil Vinegar Filtered tea 15. Answer the following questions in one sentence. 205 [Refer to Session 6.1 ] (i) Complete the table. CHAPTER 6. IS MATTER PURE?

Substance Pure substance/ not a pure Mercury substance Brick Milk Not a pure substance Calcium oxide Pure substance Iron Air Long Answer Type Questions 16. Answer the following questions in 6-8 sentences. (i) [(Session 6.3)] Write the Dispersion medium, Dispersed phase and the Colloid type for each of the examples given in the table. CHAPTER 6. IS MATTER PURE? 206

Examples Dispersion Dispersed Colloid type medium phase Foam Shaving cream Pumice stone Jelly Face cream Liquid AS5-Communication through drawing and model making Long Answer Type Questions 17. Answer the following question. (i) [(Session 6.3)] Draw a flowchart to show the classification of different states of matter. Give examples. CHAPTER 6. IS MATTER PURE? 207

18. Answer the following question. (i) [(Session 6.2)] Draw a neat diagram to show the separation of the different compo- nents of air. CHAPTER 6. IS MATTER PURE? 208

AS6-Appreciation and aesthetic sense, Values Long Answer Type Questions 19. Answer the following questions in 6-8 sentences. (i) [(Session 6.2)] What is the role of these scientists in understanding about compounds and elements? a. Isaac Newton b. Hennig Brand c. Sir Humphry Davy d. Robert Boyle e. Antoine Lavoisier AS7-Application to daily life, concern to bio diversity 209 Short Answer Type Questions CHAPTER 6. IS MATTER PURE?

20. Answer the following questions in 3-4 sentences. (i) [(Session 6.2)] What are the uses of chromatography? Long Answer Type Questions 21. Answer the following questions in 6-8 sentences. (i) [(Session 6.2)] Some solid substances if left in air, directly change into gaseous state. What is the name of this phenomenon? Give three examples of these type of sub- stances observed in your daily life. CHAPTER 6. IS MATTER PURE? 210

Objective Questions AS1-Conceptual Understanding 22. Choose the correct answer. (i) A mixture of oil in water is an example of (A) colloidal solution (B) suspension (C) emulsion (D)homogeneous solution (ii) Aerosol is an example of (B) suspension (A) solution (C) emulsion (D)colloidal Dispersion (iii) The substances which cannot be separated any further by any methods of separation are called as (A) pure substances (B) impure substances (C) mixtures (D) solutions AS2-Asking questions and making hypothesis 23. Choose the correct answer. (i) Varun mistakenly mixed water into a can containing cooking oil. Now he wants to separate both of them. What technique will you suggest him? (A) Separating funnel (B) Filtration (C) Evaporation (D)Paper Chromatography AS3-Experimentation and field investigation 24. Choose the correct answer. (i) Different pigments from an extract of flower petals can be separated by using CHAPTER 6. IS MATTER PURE? 211

(A) chromatography (B) sublimation (C) decantation (D) centrifugation (ii) A solution prepared by the addition and dissolution of maximum amount of solute in a solvent is called (A) saturated solution (B) unsaturated solution (C)aqueous solution (D)heterogeneous solution (iii) The components of ink can be efficiently separated by the technique of (A) distillation (B) filtration (C)paper chromatography (D) centrifugation (iv) ________ can be broken down by chemical or electrochemical processes. (A) Elements (B) Atoms (C) Molecules (D) Compounds AS4-Information skills and projects 25. Choose the correct answer. (i) show Tyndall effect. (B) Suspensions (A) Emulsions (C)Colloidal solutions (D)Heterogeneous solutions AS7-Application to daily life, concern to bio diversity 26. Choose the correct answer. (i) The human blood is an example of (A) compound (B) element (C)heterogeneous mixture (D) molecule CHAPTER 6. IS MATTER PURE? 212

7. ATOMS, MOLECULES AND CHEMICAL REACTIONS SESSION 1 HOW DALTON’S ATOMIC THEORY CAME INTO BEING 1.1 Mind Map 1.2 Terminology i. Laws of conservation of mass – ”Matter is neither created nor destroyed during a chemical reaction. More simply, the mass of products is equal to the mass of the reactants in a chemical reaction.” ii. Law of constant proportions – ”A given chemical substance always contains the same elements combined in a fixed proportions by mass.” iii. Postulate – A statement accepted as true for the purposes of argument or scientific investigation; also, a basic principle. SESSION 1. HOW DALTON’S ATOMIC THEORY CAME INTO BEING 213

1.3 Key Concepts i. By the end of 18th century, scientists have recognized the difference between ele- ments and compounds. ii. Afterwards the scientists proved into how and why elements combine and what hap- pens when they combine. iii. “The total mass of the reactants is equal to the total mass of the products in a chemical reaction”. This is known as law of conservation of mass. 1.4 Reflection on Concepts Q1. [AS3] Explain the process and precautions in verifying law of conservation of mass. [Refer to TB page 126 Q1] A. Law of conservation of mass states that mass of a substance can neither be created nor be destroyed in a chemical reaction. Through this experiment we can prove the mass of the reactants is equal to the mass of the products. Procedure and precautions taken in verifying law of conservation of mass: i. Prepare a solution by dissolving approximately 2 g of lead nitrate in 100 ml of distilled water. ii. Prepare another solution by dissolving approximately 2 g of potassium iodide in 100 ml water. iii. Take 100 ml solution of lead nitrate in 250 ml conical flask. iv. Also take 4 ml solution of potassium iodide in test tube. v. Hang the test tube in the flask carefully, without mixing the solutions. Put a cork on the flask. (see figure 1) vi. Weigh the flask with its contents carefully by spring balance.(see figure 2) vii. Now tilt and swirl the flask, so that the two solutions mix. viii. Weigh the flask again by the same spring balance as shown in figure 3. SESSION 1. HOW DALTON’S ATOMIC THEORY CAME INTO BEING 214

Conclusion: The mass of substances before and after a chemical reaction is same. The mass of reactants = Mass of products. Precautions: 1. Care should be taken while handling chemicals. 2. Glass apparatus should be used carefully. 3. The content of the conical flask should not mix before weighing first time. Q2. [AS1] 0.24 g sample of compound of oxygen and boron was found by analysis to contain 0.144 g of oxygen and 0.096 g of boron. Calculate the percentage composition of the compound by weight. [Refer to TB page 126 Q2] A. Boron and oxygen compound ⇒ Boron + Oxygen 0.24 g ⇒ 0.096 g + 0.144 g For boron 0.24 g of compound contains ⇒ 0.096 g of Boron 100 g contains = ? ⇒ 100 × 0.096 ÷ 0.24 = 40 % For oxygen, 0.24 g of compound contains ⇒ 0.144 g of oxygen 100 g contains = ? ⇒100 × 0.144 ÷ 0.24 = 60 % SESSION 1. HOW DALTON’S ATOMIC THEORY CAME INTO BEING 215

Q3. [AS5] Draw a diagram to show the experimental setup for the law of conservation of mass. [Refer to TB page 127 Q20] A. SESSION 1. HOW DALTON’S ATOMIC THEORY CAME INTO BEING 216

1.5 Higher Order Thinking Skills Q1. [AS2] 15.9 g of copper sulphate and 10.6 g of sodium carbonate react together to give14.2 g of sodium sulphate and 12.3 g of copper carbonate. Which law of chemical combination is obeyed? How? [Refer to TB page 128 Q1] A. Copper sulphate + Sodium carbonate = Copper carbonate + Sodium sulphate In this reaction copper sulphate and sodium carbonate are the reactants. Weight of copper sulphate = 15.9 g, Weight of sodium carbonate = 10.6 g Total weight of reactants = 15.9 g + 10.6 g = 26.5 g Sodium sulphate and copper carbonate are the products. Weight of sodium sulphate = 14.2 g Weight of copper carbonate = 12.3 g Total weight of products 14.2 g + 12.3 g = 26.5 g We find that, Total weight of reactants = Total weight of products Since total mass of reactants is equal to the total mass of products, this data proves law of conservation of mass. Q2. [AS2] Carbon dioxide is added to 112 g of calcium oxide. The product formed is 200 g of calcium carbonate. Calculate the mass carbon dioxide used. Which law of chemical combination will govern your answer? [Refer to TB page 128 Q2] A. Carbon dioxide + Calcium oxide → Calcium carbonate Mass of Carbon dioxide +112 g → 200 g Mass of carbon dioxide = 200g –112 g = 88 g Mass of CO2 required is 88 g. 88 g + 112 g = 200 g The law demonstrated in this reaction is law of conservation of mass. In this reaction 2 moles of CO2 combines with 2 moles of CaO to give two moles of CaCO 3 . SESSION 1. HOW DALTON’S ATOMIC THEORY CAME INTO BEING 217

1.6 Suggested Experiments Q1. [AS3] Do an experiment to understand the changes in weight of reactants and products in a chemical reaction, write a report. [Refer to TB page 129 Q1] A. Law of conservation of mass states that mass of a substance can neither be created nor be destroyed in a chemical reaction. Through this experiment we can prove the mass of the reactants is equal to the mass of the products. Procedure : i. Prepare a solution by dissolving approximately 2 grams of lead nitrate in 100 ml of distilled water. ii. Prepare another solution by dissolving approximately 2 g of potassium iodide in 100 ml water. iii. Take 100 ml solution of lead nitrate in 250 ml conical flask. iv. Also take 4ml solution of potassium iodide in test tube. v. Hang the test tube in the flask carefully, without mixing the solutions. Put a cork on the flask. (see figure 1) vi. Weigh the flask with its contents carefully by spring balance.(see figure 2) vii. Now tilt and swirl the flask, so that the two solutions mix. viii. Weigh the flask again by the same spring balance as shown in figure 3. Fig.1 Fig.2 Fig.3 Conclusion: The mass of substances before and after chemical reaction is same. The mass of reactants = Mass of products. SESSION 1. HOW DALTON’S ATOMIC THEORY CAME INTO BEING 218

SESSION 2 ATOMS, MOLECULES AND ELEMENTS 2.1 Mind Map SESSION 2. ATOMS, MOLECULES AND ELEMENTS 219

2.2 Terminology i. Atom – An atom is the smallest particle of an element that can participate in a chem- ical reaction and retain all its properties. ii. Symbol – Symbol is the shortened form to denote the name of an element. iii. Atomic mass – The atomic mass of an element is defined as the average mass of all the isotopes of the element as compared to 1/12th of the mass of one carbon –12 atom. iv. Atomic mass unit (a.m.u.) – One atomic mass unit (amu) is defined as the mass exactly one twelfth the atomic mass of Carbon–12 isotope. v. Unified mass (µ) – The unified atomic mass unit (symbol: u) or dalton (symbol: Da) is the standard unit that is used for indicating mass on an atomic or molecular scale (atomic mass). vi. Molecule – A molecule is the smallest particle of an element or a compound that is capable of independent existence and retains all the properties of that substance. SESSION 2. ATOMS, MOLECULES AND ELEMENTS 220

2.3 Key Concepts i. An atom is the smallest particle of an element that can participate in chemical reac- tions and retain all its properties. ii. A molecule is the smallest particle of an element or a compound that is capable of independent existence and retains all the properties of that substance. iii. Symbol is the shortened form to denote the name of element. iv. Scientists use the relative atomic mass scale to compare the masses of different atoms of elements. v. The number of times one atom of an element is heavier than 1/12th part of the mass of a carbon –12 atom is called its atomic mass. It is denoted as a.m.u. or simply u. vi. We can write the formula of any compound by applying criss–cross method. 2.4 Reflection on Concepts Q1. [AS1] In a class, a teacher asked the students to write the molecular formula of oxygen. Shamita wrote the formula as O2 and Priyanka as O. Which one is correct? State the reason. [Refer to TB page 126 Q3] A. The molecular formula of oxygen written by Shamita is correct and formula written by Priyanka is not correct. The correct molecular formula of oxygen is O2 . Steps for writing the formula of an element: i. Write the symbol of oxygen: O. ii. The valency of oxygen is ‘2’. iii. So write 2 as subscript on the right side of the symbol. iv. So the correct way of writing the molecular formula is O2 . Q2. [AS1] Write the valencies of Fe in FeCl2 and FeCl3 . [Refer to TB page 126 Q9] A. i. Valency is the combining capacity of an element or group of atoms. ii. The valency of Cl (Chloride) is 1. iii. Cl2 indicates 1 x 2 = 2. iv. In FeCI2 , one atom of iron (Fe) is combining with two chloride ion. So, from FeCl2 the valency of Fe is 2. v. In FeCI3, one atom of iron (Fe) is combining with three chloride ions. So from FeCl3 the valency of Fe is 3. SESSION 2. ATOMS, MOLECULES AND ELEMENTS 221

Q3. [AS1] Which has more number of atoms –100 g of sodium or 100 g of iron? Justify your answer. (Atomic mass of sodium = 23 u, atomic mass of iron = 56 u) [Refer to TB page 126 Q11] A. 23 g of Na is 1 mole and has 6.022 × 1023 atoms 100 g of Na =? 100×6.022×1023 23 = 602.2 × 1023 23 = 26.182 × 1023 = 2.6182 × 1024 atoms 56 g of iron has 6.022 × 1023 atoms. 100 g of iron =? 100×6.022×1023 56 = 602.2 × 1023 56 = 10.753 × 1023 = 1.075 × 1024 100 g of Na contain 2.618 × 1024 atoms 100 g of Fe contain 1.075 × 1024 atoms So, 100 g of sodium contains more atoms than 100 g of iron. Q4. [AS1] Complete the following table: [Refer to TB page 127 Q13] SESSION 2. ATOMS, MOLECULES AND ELEMENTS 222

A. Chloride Hydroxide Nitrate Sulphate Carbonate Phosphate Anions Cations Sodium NaCl NaOH NaNO3 Na2SO4 Na2CO3 Na3PO4 Mg(OH)2 Mg(NO3)2 MgSO4 MgCO3 Mg3(PO4)2 Magnesium MgCl2 Ca(OH)2 Ca(NO3)2 CaSO4 CaCO3 Ca3(PO4)2 Al(OH)3 Al(NO3)3 Al2(SO4)3 Al2CO3 AlPO4 Calcium CaCl2 NH4OH NH4NO3 (NH4)2SO4 (NH4)2CO3 (NH4)3PO4 Aluminium AlCl3 Ammonium NH4Cl Q5. [AS1] Lakshmi gives a statement “CO and Co both represent elements”. Is it correct? State the reason. [Refer to TB page 126 Q4] A. It is wrong. CO = Carbon monoxide Co = Cobalt CO is carbon monoxide, where C and O represent the different elements present in the compound carbon monoxide. This can be identified with the help of both C and O, which are capital(upper case) letters. Co represents an element, where the first letter is capital (upper case) and the second letter is small(lower case). SESSION 2. ATOMS, MOLECULES AND ELEMENTS 223

2.5 Higher Order Thinking Skills Q1. [AS2] Imagine what would happen if we do not have standard symbols for elements? [Refer to TB page 128 Q3] A. i. If we do not have standard symbols for elements, we have to write the complete names of elements and compounds which would be time consuming and labori- ous. ii. So, the standard symbols have enabled students of science to write the names of chemical substances and represent chemical reactions in a precise manner. SESSION 2. ATOMS, MOLECULES AND ELEMENTS 224

SESSION 3 MOLECULES, MOLE CONCEPT,TYPES OF CHEMICAL REACTIONS 3.1 Mind Map 3.2 Terminology i. Chemical formula –A set of chemical symbols showing the elements present in a compound and their relative proportions. ii. Ion (cation, anion) –An electrically charged atom or group of atoms formed by the loss or gain of one or more electrons, as a cation (positive ion ) which is created by electron loss or as an anion (negative ion ) which is created by electron gain. iii. Valency – Valency of an element is a measure of its combining power with other atoms when it forms chemical compounds or molecules. iv. Molecular mass –The molecular mass of a substance is the sum of the atomic masses of all the atoms in a molecule of the substance. SESSION 3. MOLECULES, MOLE CONCEPT, TYPES OF CHEMICAL REACT... 225

v. Formula unit mass – The formula unit mass of a substance is the sum of the atomic masses of all constituent atoms in a formula unit of a compound. vi. Mole –One mole of a substance is the amount of the substance which contains as many particles (atoms, molecules, ions, etc.) or entities that are equal to the atoms present in exactly 12 grams of 12C isotope. vii. Avogadro constant – The number of particles present in one mole of any substance is known as Avogadro constant (NA ) and it has a constant value of 6.022 x 1023. viii. Molar mass –The mass of 1 mole of a substance which is expressed in grams is called molar mass. ix. Chemical combination –A reaction in which single product is formed from two or more reactants. x. Chemical decomposition –A reaction in which single reactant decomposes into two or more products. xi. Displacement reaction –In this reaction one element displaces another element from its compound and takes its place there in. xii. Double replacement reaction –In this reaction two reactants exchange their con- stituents chemically and form two products. xiii. Photochemical reaction –It is a decomposition reaction occurs in presence of sunlight. xiv. Oxidation –It is a reaction that involves the addtion of oxygen or removal of hydrogen. xv. Molecules antioxidants –A substance that prevents the oxidation of others. xvi. Reduction –It is a reaction that involves the addition of hydrogen or removal of oxygen. xvii. Redox reaction –Oxidation and reduction occur in a single reaction. xviii. Corrosion –When some metals are exposed to moisture, acids etc.,they tarnish due to the formation of respective metal oxide on their surface. This process is called as corrosion. xix. Galvanizing –It is a method of protecting iron from rusting by coating them with thin layer of Zinc. xx. Alloy – A metallic substance made by mixing and fusing two or more metals, or a metal and a nonmetal, to obtain desirable qualities such as hardness, lightness, and strength is known as alloy. xxi. Rancidity –Oxidation reaction in food material that were left for a long period. SESSION 3. MOLECULES, MOLE CONCEPT, TYPES OF CHEMICAL REACT... 226

3.3 Key Concepts i. The number of particles present in one mole of any substance is known as Avogadro constant (NA ) and it has a constant value of 6.022 x 1023. ii. The mass of 1 mole of a substance which is expressed in grams is called molar mass. iii. One mole of a substance is the amount of the substance which contains as many par- ticles (atoms, molecules, ions) or entities that are equal to the atoms present in exactly 12 grams of 12C isotope. iv. A chemical reaction is a process that is usually characterized by a chemical change in which the starting materials (reactants) are different from the products. Chemical reaction occurs with the formation and breaking of chemical bonds. v. A reaction in which single product is formed from two or more reactants is known as chemical combination reaction. vi. In a decomposition reaction reactant decomposes into two or more products. vii. Photochemical reaction is a decomposition reaction with happens in presence of sun light. viii. On passing electricity, water dissociates to hydrogen and oxygen. This is called electrolytic reaction. SESSION 3. MOLECULES, MOLE CONCEPT, TYPES OF CHEMICAL REACT... 227

3.4 Reflection on Concepts Q1. [AS1] Find out the chemical names and formulae for the following common household substances: [Refer to TB page 126 Q5] (a) common salt (b) baking soda (C) washing soda (d) vinegar. A. S.No. Name of substance Chemical Name Formula 1 Common salt Sodium chloride NaCl 2 Baking soda Sodium NaHCO3 bicarbonate 3 Washing soda Sodium carbonate Na2 CO3 4 Vinegar Acetic acid CH3 COOH Q2. [AS1] Calculate the mass of the following: [Refer to TB page 126 Q6] a. 0.5 mole of N2 gas b. 0.5 mole of N atoms c. 3.011 × 1023 number of N atoms d. 6.022 × 1023 number of N2 molecules A. (a) 0.5 mole of N2 gas: 1 mole of N2 gas has mass=28 g 0.5 mole of N2 gas has mass = 0.5 × 28g = 14g (b) 0.5 mole of N atoms: Mass of 1 mole of N atoms = 14 g Mass of 0.5 mole of N atoms = 0.5 × 14 = 7g SESSION 3. MOLECULES, MOLE CONCEPT, TYPES OF CHEMICAL REACT... 228

(c) 3.011 × 1023 number of N atoms: Mass of 6.022 × 1023 N atoms = 14 g Mass of 3.011 × 1023 N atoms = 7 g (d) 6.022 × 1023 number of N2 molecules: Mass of 1 mole of N2 molecules = Mass of 6.022 × 1023 number of N2 molecules = 28 g Q3. [AS1] Calculate the number of particles in each of the following: [Refer to TB page 126 Q7] (a) 46 g of Na atoms (b) 8 g of O2 molecules (c) 0.1 mole of hydrogen atoms A. (a) 46 g of Na atoms: Atomic mass of Na = 23 g No. of moles of Na atoms in 46 g of Na = 2 ∴ 2 moles of Sodium contain = 2 × 6.022 × 1023 = 1.204 × 1024 atoms (b) 8 g of O2 molecules Molecular mass of O2 = 32 g 32 g of O2 contains 6.022 × 1023 molecules 8 g of O2 contains (6.022 × 1023) ÷ 4 = 1.5055 × 1023 molecules (c) No. of moles of hydrogen atoms = 0.1 No. of particles of hydrogen in 0.1 moles = 0.1 × 6.022 × 1023 = 6.022 × 1022 atoms Q4. [AS1] Convert into moles: [Refer to TB page 126 Q10] (a) 12 g of O2 gas (b) 20 g of Water (c) 22 g of Carbon dioxide A. a) 12 g of O2 gas SESSION 3. MOLECULES, MOLE CONCEPT, TYPES OF CHEMICAL REACT... 229

32 g of O2 = 1 mole ∴ 12 g of O2 = 12 ÷ 32 = 0.375 moles b) 20 g of Water 18 g of water = 1 mole ∴ 20 g of water = 20 ÷ 18 = 1.12 moles c) 22 g of Carbon dioxide 44 g of carbon dioxide = 1 mole ∴ 22 g of carbon dioxide= 22 ÷ 44 = 0.5 moles Q5. [AS1] Calculate the molar mass of sulphuric acid (H2 SO4 ) and glucose (C6 H12 O6 ). [Refer to TB page 126 Q10] A. a) Molecular mass of sulphuric acid H2 SO4 : (Recall : Atomic masses of H =1, S = 32 and O = 16) Molecular mass of H 2 SO4 = 2 × 1 + 32 + 4 × 16 = 2 + 32 + 64 =98 g b) Molecular mass of glucose (C6 H12 O6 ): (Recall : Atomic masses of C = 12, H =1, O = 16) Molecular mass of C6H12O6 = 6 × 12 + 12 × 1 + 6 × 16 = 72 + 12 + 96 = 180 g Q6. [AS1] Fill the following table [Refer to TB page 127 Q12] SESSION 3. MOLECULES, MOLE CONCEPT, TYPES OF CHEMICAL REACT... 230

S.No. Name Symbol / Mmoalsasr Number of particles Formula 16 g Present in molar mass 1 Atomic oxygen 6.022 × 1023 atoms of oxygen 2 Molecular oxygen 3 Sodium 4 Sodium 23 g ion 6.022 × 1023 units of 5 Sodium sodium chloride chloride 6 Water A. S.No. Name Symbol / Mmoalsasr Number of particles Formula Present in molar mass 1 Atomic O 16 g 6.022 × 1023 atoms of oxygen oxygen 2 Molecular O2 32 g 12.044 × 1022 atoms oxygen of oxygen 3 Sodium Na 23 g 6.022 × 1023 atoms of sodium 4 Sodium Na+ 23 g 6.022 × 1023 atoms of ion sodium ion 5 Sodium NaCl 58.5 g 6.022 × 1023 units of chloride sodium chloride 6 Water H2O 18 g 6.022 × 10 23 units of water SESSION 3. MOLECULES, MOLE CONCEPT, TYPES OF CHEMICAL REACT... 231

Q7. [AS1] Write an equation for decomposition reaction where energy is supplied in the form of heat or light or electricity. [Refer to TB page 127 Q13] A. i. CaCO3(s) Heat CaO(s) + CO2 (g) Heat Energy ii. 2AgBr(s) Heat 2Ag(s) + Br2 (g) Light Energy iii. 2H2O(l) Electrolysis 2H2 (g) + O2 (g) Electricity Q8. [AS1] Name the reactions taking place in the presence of sunlight? [Refer to TB page 127 Q15] A. Photochemical Reaction Q9. [AS1] In the refining of silver, the recovery of silver from silver nitrate solution, in- volves displacement by copper metal. Write the reaction involved. [Refer to TB page 127 Q19] A. Cu(s) + 2AgNO3(aq) → Cu(NO3)2(aq) + 2Ag(s) Copper + S ilver nitrate → Copper nitrate + S ilver Q10. [AS2] How chemical displacement reactions differ from chemical decomposition reac- tion? Explain with an example for each. [Refer to TB page 127 Q14] A. In chemical displacement reaction, one element displaces another element from its com- pound and takes its place there in. For example: Displacement of hydrogen from acids by metals. Zn (s) + 2HCl (aq) → ZnCl2 (aq) + H2 In the above reaction the element zinc has displaced hydrogen from hydrochloric acid. This is displacement reaction. In chemical decomposition reaction, one reactant decomposes into one or more prod- ucts in the presence of heat, light or electricity. For example: Decomposition of Lime stone into quick lime. SESSION 3. MOLECULES, MOLE CONCEPT, TYPES OF CHEMICAL REACT... 232

On heating calcium carbonate decomposes to calcium oxide and carbon dioxide. CaCO3 (s) → CaO (s) + CO2 (g) Lime stone quick lime It is a thermal decomposition reaction. Q11. [AS2] Why does respiration considered as an exothermic reaction? Explain. [Refer to TB page 127 Q16] A. Respiration is considered as an exothermic reaction because in respiration oxidation of glucose takes place which produces large amount of heat energy. This is shown in following chemical equation. C6H12O6 (aq) + 6O2 (g) → 6CO2 (g) + 6H2O (l) + Energy Q12. [AS2] What is the difference between displacement and double displacement reactions? Write equations for these reactions? [Refer to TB page 127 Q17] A. In displacement reaction one element displaces another element from its compound and takes its place there in. Displacement of hydrogen from acids by metals: Generally metals which are more active than hydrogen displace it from an acid. Zn (s) + 2HCl (aq) → ZnCl2 (aq) + H2 (g) If two reactants exchange their constituents chemically and form two products, then the reaction is called as double displacement reaction. Pb NO3 2 (aq) + 2KI (aq) → PbI2 (s) + 2KNO3 (aq) Thus in displacement only one element is displaced while in double displacement, two elements are displaced. Q13. [AS7] Give two examples for oxidation–reduction reaction. [Refer to TB page 127 Q18] A. The examples for oxidation–reduction reaction. i) 2Fe2O3 (s) + 3C (s) → 4Fe (s) + 3CO2 (g) ii) 2PbO (s) + C (s) → 2Pb (s) + CO2 (g) SESSION 3. MOLECULES, MOLE CONCEPT, TYPES OF CHEMICAL REACT... 233

3.5 Application of Concepts Q1. [AS1] Why do we apply paint on iron articles? [Refer to TB page 127 Q1] A. Iron articles are painted to prevent them from rusting. After painting iron surface does not come in contact with moisture and air which cause rusting. Q2. [AS1] What is the use of keeping food in air tight containers? [Refer to TB page 127 Q2] A. It does not allow air (oxygen) to come in contact with the food and this prevents oxidation of food. Thus the food never become rancid and its smell and taste remains the same. 3.6 Suggested Projects Q1. [AS4] Collect the information about the symbols, atomic weights of first therty elements in the periodic table and write a report. [Refer to TB page 129 Q1] A. Student’s Activity (Hint: Refer Mendeleev’s periodic table ) Objective Questions (1) Fe2O3 + 2Al → Al2O3 + 2Fe The above reaction is an example of: (Pg 128;TB Q1) (A) Combination reaction (B) Decomposition reaction (C) Displacement reaction (D)Double decomposition reaction Correct Answer: C SESSION 3. MOLECULES, MOLE CONCEPT, TYPES OF CHEMICAL REACT... 234

(2) What happens when dil. hydrochloric acid is added to iron filings? Choose the correct answer.(Pg 128;TB Q 2) (A) Hydrogen gas and iron chloride are produced (B) Chlorine gas and iron hydroxide are produced (C)No reaction takes place (D)Iron, salt and water are produced Correct Answer: A (3) 2PbO(s) + C(s) → 2Pb(s) + CO2(g) Which of the following statements is/are correct for the above chemical reaction?(Pg 128;TB Q 3) (A) Lead oxide is reduced (B) Carbon dioxide is oxidized (C)Carbon is oxidized (D)(a) and (c) are correct Correct Answer: D (4) The chemical equation BaCl2 + Na2S O4 → BaS O4 + 2NaCl represents following type of chemical reaction. (Pg 128;TB Q 4) (A) Displacement (B) Combination (C) Decomposition (D) Double–displacement Correct Answer: D (5) The reaction for formation of hydrogen chloride from hydrogen and chlo- ride represents following type of chemical reaction. (Pg 129; TB Q 5) (A) Decomposition (B) Displacement (C) Combination (D) Double–displacement Correct Answer: C SESSION 3. MOLECULES, MOLE CONCEPT, TYPES OF CHEMICAL REACT... 235

—— CCE Based Practice Questions —— AS1-Conceptual Understanding Very Short Answer Type Questions 1. Match the following. [(Session 7.3)] [] Column B Column A [] a. HNO3 i. Sodium carbonate [] b. H2 SO4 [] c. Na2 CO3 ii. Copper sulphate [] d. CuSO4 e. NaHCO3 iii. Sodium bicarbonate iv. Nitric acid v. Sulphuric acid 2. Match the following. [(Session 7.1)] Column A Column B i. Father of modern chemistry [ ] a. Joseph L. Proust ii. Chemical compound always combine [ ] b. John Dalton in a fixed proportion iii. Atoms are neither created nor destroyed [ ] c. John Berzelius iv. Initial letter of element should be in [ ] d. Kanada capitals v. Vaishesika Sutra [ ] e. Antoine Lavoisier 3. Fill in the blanks. [Refer to Session 7.1 ] (i) Matter is neither nor during a chemical reaction. CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 236

(ii) Matter is made of particles called . (iii) Chemical reaction involves of atoms. (iv) Atoms of same element have mass and chemical properties. (v) Compounds are formed when atoms of different elements combine in simple ratios. Short Answer Type Questions 4. Answer the following questions in 3-4 sentences. (i) [(Session 7.2)] What are the two types of ions? (ii) [(Session 7.2)] Which two elements combine to form water? What is the formula of water and what information do you get from it? 5. Answer the following questions in 3-4 sentences. (i) [(Session 7.3)] Define molar mass and write the value of one mole. CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 237

(ii) [(Session 7.3)] Write a note on formula unit mass. (iii) [(Session 7.3)] Explain the chemical combination reaction with suitable example? (iv) [(Session 7.3)] Name the reaction taking place in the presence of sunlight. (v) [(Session 7.3)] Convert the following into mole. 238 a) 12 g of O2 gas; b) 20 g of water; c) 22 g of carbon dioxide CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS

(vi) [(Session 7.3)] What is the formula unit mass of sodium chloride? 6. Answer the following questions in 3-4 sentences. (i) [(Session 7.1)] State the law of conservation of mass. (ii) [(Session 7.1)] What are the postulates of Dalton’s atomic theory? CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 239

Long Answer Type Questions 7. Answer the following questions in 6-8 sentences. (i) [(Session 7.2)] Calculate the number of atoms present in 0.1 mole of Na and 2.3 g of Na. Are the number of atoms same in both the cases? (ii) [(Session 7.2)] Write the chemical formula of the following elements. a. Calcium hydroxide b. Calcium nitrate c. Calcium chloride d. Calcium sulphate e. Calcium phosphate Knowing that valency of calcium is 2, find out the valency of the anions in the above compounds. Using this information, write the formula and name all the compounds formed by these anions with magnesium and aluminum as the cations. CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 240

(iii) [(Session 7.2)] Calculate the formula unit mass of ZnO, Na2 O, K2 CO3 . (Given atomic masses of zinc = 65, oxygen = 16, sodium = 23, potassium = 39, carbon = 12.) 8. Answer the following questions in 6-8 sentences. (i) [(Session 7.3)] Convert into moles: a. 18 g of H2O b. 44 g of CO2 c. 23 g of Na CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 241

(ii) [(Session 7.3)] Distinguish between a molecule and a compound. CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 242

(iii) [(Session 7.3)] What do you mean by corrosion? How can you prevent it? (iv) [(Session 7.3)] How does a chemical displacement reaction differ from chemical de- composition reaction? Explain with examples. CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 243

9. Answer the following questions in 6-8 sentences. (i) [(Session 7.1)] Water taken from any source has the same percentage of oxygen and hydrogen. Who discovered this? What is the law he proposed? Is this valid for every composition of chemical compound? (ii) [(Session 7.1)] State the law of constant proportion. How can you explain this based on Dalton’s atomic theory? Explain it taking an example of water. CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 244

AS2-Asking questions and making hypothesis Short Answer Type Questions 10. Answer the following questions in 3-4 sentences. (i) [(Session 7.2)] Helium is He, Oxygen is O2 , and Sulphur is S8 . Why do you think the formula of each of these molecules is different? Give reasons. (ii) [(Session 7.2)] Raju sees two symbols CO and Co. One is cobalt and the other one is carbon monoxide. What doubts would arise in his mind regarding the meaning of elements and compounds? CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 245

Long Answer Type Questions 11. Answer the following questions in 6-8 sentences. (i) [(Session 7.2)] Imagine what would happen if we did not have standard symbols for elements. 12. Answer the following questions in 6-8 sentences. (i) [(Session 7.3)] Comment on the statement: “A molecule is the smallest particle of a substance which has the properties of the substance and is stable.” CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 246

AS3-Experimentation and field investigation Long Answer Type Questions 13. Answer the following questions in 6-8 sentences. (i) [(Session 7.3)] Teacher conducted an experiment. On passing electricity, water dis- sociates into hydrogen and oxygen. a. What materials did he use to conduct the experiment? b. What do you observe in the test tubes? c. Is the volume of gas collected in both the test tubes same? d. Can you predict the gas present in each test tube? CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 247

(ii) [(Session 7.3)] Teacher gave pinch of calcium carbonate (CaCO3 ) to perform an ex- periment for thermal decomposition. a) What material did you use? b) How did you arrange the apparatus? c) How did you perform the experiment? d) What did you conclude with the experiment? CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 248