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

(iii) [(Session 7.3)] Teacher gave a chemical equation to perform an experiment. Pb(NO3)2(aq) + 2KI(aq) → PbI2(s) + 2KNO3(aq) a. Identify the type of chemical reaction. b. What is the material required to conduct the experiment? c. What are the observations you get from it? d. What are the new substances formed as a product? (iv) [(Session 7.3)] Take about 1 g of copper in a china dish, keep the china dish on a tripod stand containing wire gauge, heat with Bunsen burner. CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 249

a. Do you find any change in colour of copper? b. Why does the colour of copper change? c. Write down the chemical equation. d. Write the type of reaction. 14. Answer the following questions in 6-8 sentences. (i) [(Session 7.1)] Suggest an experiment to prove that mass is neither created nor de- stroyed during a chemical reaction. What is the law corresponding to this experiment? CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 250

CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 251

AS4-Information skills and projects Long Answer Type Questions 15. Answer the following questions in 6-8 sentences. (i) [(Session 7.2)] Complete the table. Element Symbol Valency Carbon O F Hydrogen Argon CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 252

16. Answer the following questions in 6-8 sentences. (i) [(Session 7.3)] Find out the chemical names and formulae for the following com- mon household substances: (a) common salt; (b) baking soda; (c) washing soda; (d) vinegar. AS5-Communication through drawing and model making Long Answer Type Questions 17. Answer the following questions. (i) [(Session 7.3)] Draw the diagram for electrolysis of water and label the parts. CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 253

(ii) [(Session 7.3)] Draw the diagram for heating of calcium carbonate and test the gas evolved by burning a match stick. Label the parts. 18. Answer the following question. (i) [(Session 7.1)] Draw a diagram to show the experimental setup for the law of conser- vation of mass. CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 254

AS6-Appreciation and aesthetic sense, Values Short Answer Type Questions 19. Answer the following questions in 3-4 sentences. (i) [(Session 7.2)] Why do you appreciate Kanada? AS7-Application to daily life, concern to bio diversity Long Answer Type Questions 20. Answer the following questions in 6-8 sentences. (i) [(Session 7.3)] Verify by calculating, that: a) 5 moles of carbon dioxide and 5 moles of water do not have the same mass. b) 240 gram of calcium and 240 gram of magnesium have a mole ratio of 3:5. CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 255

Objective Questions AS1-Conceptual Understanding 21. Choose the correct answer. (i) When 50 gram of calcium carbonate is heated, 22 gram of CO 2 escapes out. What is the amount of residue left? (A) Cannot be found (B) More data is required (C)56 gram (D)28 gram (ii) The total number of atoms present in 1 molecule of the elementary substance is called ______________________ . (A) atomic number (B) avogadro number (C)atomic mass (D) atomicity (iii) In water, hydrogen and oxygen are present in the ratio of by mass. (A) 1:8 (B) 2:3 (C) 2:1 (D) 1:2 (iv) The number of particles in a mole of a substance is always constant. This is called as (A) Avogadro’s constant (B) Atomic number (C)Formula unit mass (D)Molar mass AS2-Asking questions and making hypothesis 22. Choose the correct answer. (i) Which of the following supports Dalton’s atomic theory of matter? (A) Formation of isotopes (B) Formation of isobars CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 256

(C)Law of definite proportions (D)Graphite and diamond though made from carbon, show different properties AS3-Experimentation and field investigation 23. Choose the correct answer. (i) Vijay wants to measure 12.044 X 10 23 atoms of sodium. How many moles of sodium he has to take? (A) 1 mole (B) 2 moles (C)3 moles (D)4 moles AS4-Information skills and projects 24. Choose the correct answer. (i) Choose the odd molecule. (B) Chlorine molecule (A) Argon molecule (C)Bromine molecule (D)Fluorine molecule (ii) A mole does not signify: (B) 6.023 x 1023 (A) atomic mass unit (C)22.4 litres of a gas at STP (D)gram molecular mass (iii) Atomic mass of calcium is 40. The mass of 2.5 gram atoms of calcium is . (A) 40 grams (B) 2.5 grams (C)100 grams (D)80 grams CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 257

(iv) Empirical formula of a substance is CH2O. Molar mass is 180 g. What is the chemical formula? (A) C6 H12 O6 (B) C22 H12 O7 (C)C2 H5 OH (D)C12 H22 O11 AS6-Appreciation and aesthetic sense, Values 25. Choose the correct answer. (i) Alloying is a good method of improving properties of . (A) non-metals (B) plastics (C) wood (D) metals AS7-Application to daily life, concern to bio diversity 26. Choose the correct answer. (i) Decomposition occurs in presence of sunlight and such reaction called _______. (A) gamma physical reaction (B) photochemical reaction (C)artificial reaction (D)none of these (ii) The browning of iron, when left for a while in moist air _________. (A) reduction reaction (B) oxidation reaction (C)anti–oxidant reaction (D)no reaction CHAPTER 7. ATOMS, MOLECULES AND CHEMICAL REACTIONS 258

8. FLOATING BODIES SESSION 1 INTRODUCTION, DENSITY AND RELATIVE DENSITY 1.1 Mind Map 1.2 Terminology i. Density – Mass per unit volume. ii. Relative density –The ratio of the density of the object to density of water. iii. Lactometer – A device used to measure the relative density of milk. iv. Hydrometer –Device to measure the relative density of liquids. 1.3 Solved Examples Q1. Example 1: What is the effective density of the mixture of water and milk when [Refer to TB page 135] SESSION 1. INTRODUCTION, DENSITY AND RELATIVE DENSITY 259

i. they are taken with same masses ii. they are taken with same volumes A. Let us say the densities of water and milk are ρ1 and ρ2 . i) When they are taken with same mass ‘m’ and their volumes are V1 and V2 , the mass m m of water m = ρ1 V1 ; V1 = ρ1 and the mass of milk m = ρ2 V2 ; V2 = ρ2 Total mass of water and milk is m + m = 2m Total volume of water and milk is V1 + V2 = m + m =m 1 + 1 = m(ρρ11+ρ2ρ2) ρ1 ρ2 ρ1 ρ2 The effective density of the mixture (ρe f f ) = T otal mass = 2m = 2 = T otal volume m(ρρ11ρ+2ρ2) (ρρ11+ρρ22) 2ρ1 ρ2 ρ1+ρ2 ii) When they are taken with same volume ‘V’ and their masses are m1 and m2, the m1 volume of water V = ρ1 That is m1 = Vρ1 and the volume of milk V = mρ2 2 That is m2 = Vρ2 Total mass of water and milk is m1 + m2 = Vρ1 + Vρ2 = V (ρ1 + ρ2 ) Total volume of water and milk is V + V = 2V The effective density of the mixture (ρe f f ) = T otal mass T otal volume ρe f f = V (ρ1 +ρ2 ) = 1 (ρ1 + ρ2) 2V 2 1.4 Key Concepts i. We find some bodies float on water and some sink. ii. Objects which have a density less than the liquid in which they are kept, float on the surface of the liquid. iii. The relative density of a substance is the ratio of the density of the substance to the density of water. It is a ratio of similar quantities and has no unit. SESSION 1. INTRODUCTION, DENSITY AND RELATIVE DENSITY 260

1.5 Reflection on Concepts Q1. [AS1] Explain density and relative density and write formulae. [Refer to TB page 148 Q2] A. Density is mass per unit volume mass. Density = Mass/ Volume. Units of density are g/cm3 or kg/cm3. Relative density is the ratio between the density of a substance and the density of wa- ter. To find the relative density of an object, we must first weigh the object and then weigh an equal volume of water. The two weights are then compared. So, relative density of an object = Density of an object/ Density of water Relative density is a ratio. So it has no units. Q2. [AS3] How can you find the relative density of a liquid. [Refer to TB page 148 Q4] A. Aim : To find the relative density of a liquid. Material required: Small bottle of 50 ml capacity (the bottle should weigh not less than10g), spring balance, any liquid (milk or oil or kerosene) about 50 ml. Procedure: 1. Find the weight of empty 50 ml bottle. 2. Fill the bottle with water and weigh it. 3. Find the weight of 50 ml water. 4. Replace the water with milk(or any other liquid) in the bottle. 5. Weigh the bottle with liquid. 6. Weight of 50 ml liquid = Weight of bottle with liquid - Weight of empty bottle 7. Relative density o f liquid = Weight o f the liquid Weight o f same volume o f water SESSION 1. INTRODUCTION, DENSITY AND RELATIVE DENSITY 261

S.No. Name Weight Weight Weight Weight Weight Relative of the of of of of of density liquid empty bottle water bottle liquid of liquid bottle with with water liquid 1.6 Application of Concepts Q1. [AS1] A solid sphere has a radius of 2 cm and a mass of 0.05 kg. What is the relative density of the sphere? [Refer to TB page 148 Q1] A. Radius = 2 cm Volume = 4 πr3 = 4 × 22 × 23 3 3 7 Mass = 0.05 kg = 50 g Density of sphere = Mass of solid = 50×3×7 = 1.49g/cc Volume of solid 4×22×8 Relative density of the sphere is also 1.49, as relative density is the ratio of densities of object to the water and density of water is 1 g/cc. Q2. [AS1] A small bottle weighs 20 g when empty and 22 g when filled with water. When it is filled with oil, it weighs 21.76 g. What is the density of oil? [Refer to TB page 148 Q2] A. Weight of oil = 21.76 – 20 = 1.76 g Weight of water = 22 – 20 = 2 g Density = 1.76 = 0.88g/cm3 2 SESSION 1. INTRODUCTION, DENSITY AND RELATIVE DENSITY 262

1.7 Higher Order Thinking Skills Q1. [AS3] Do all objects that sink in water, sink in oil ? Give reason. A. i) No, all objects that sink in water, don’t sink in oil. ii) Oil is less dense than water as it floats on the surface of anybody of water. iii) Due to the differences in the density of water and oil, some objects which sink in water may float in oil. iv) Some objects which sink in water they too sink in oil also. v) This is all depending up on the densities of water, oil and substance what we are taking to test. 1.8 Suggested Experiments Q1. [AS3] Conduct an experiment to find the relative densities of different substances and write a report. [Refer to TB page 149 Q1] A. Aim: Finding the relative density of different objects. Materials required: Overflow vessel, 50 ml measuring cylinder, weighing balance and weights or spring balance, rubber erasers, wooden blocks, glass slides, iron nails, plastic cubes, piece of aluminium sheet, glass marbles, stones, cork etc. (note: whatever object you take, ensure that its volume is more than 20 cc and it should not be hollow). Record the results of your activity in table. Table S. No. Name of Weight Weight Weight Relative (1) object of dis- of water density of object placed of the water dis- object (2) (3) placed and by the (6) cylinder object (4) (5) Weigh the 50 ml measuring cylinder and note its weight here. Weight = . . . . . . . . . . . . . . . . . . . Procedure: i. Weigh the object, record this in column 3 of the Table. ii. We need to find the weight of water equal to the volume of the object. SESSION 1. INTRODUCTION, DENSITY AND RELATIVE DENSITY 263

iii. Pour water in the overflow vessel until it starts dripping from its beak. iv. When water stops dripping from the beak, place the 50 ml measuring cylinder under it. v. Slip the object gently into the overflow vessel as shown in figure, ensuring that water does not splash out. vi. Once the object is in the overflow vessel, water flows out of the beak and collects in the 50 ml cylinder. Wait till the flow stops. (The object should be fully immersed in water. If the object is not fully immersed, push it in to the water with a pin.) vii. Weigh the cylinder with the water that overflowed and record the weight in column 4. viii. If we subtract the weight of the measuring cylinder from this weight, we get the weight of water (column 5 of the table). This is the weight of water equal to the volume of the object. ix. Now we can find the relative density of the object (column 6) by taking the weight of the object (column 3) and dividing it by the weight of an equal volume of water (column 5). x. This tells us how many times denser the object is, compared to water. Relative density of an object = Weight of the object Weight of water equal to the volume of the object Find the relative densities of all objects you collected. SESSION 1. INTRODUCTION, DENSITY AND RELATIVE DENSITY 264

1.9 Suggested Projects Q1. [AS3] Find the relative density of different fruits and vegetables and write a list. [Refer to TB page 149 Q2] A. S. No. Fruit/ Vegetable Relative density 1 Custard Apple 0.650 2 Banana 1.14 3 Almonds 1.16 4 Pomegranate 0.920 5 Grapes 1.044 6 Cabbage 0.36 7 Potato 0.67 8. Onion 0.59 9 Chilli 0.29 10 Cauliflower 0.26 11 Apple 1.22 Objective Questions (B) cm/g3 (1) Unit of relative density is (pg 148;Q 1) (D)No units (A) g/cm3 (C) N/m2 Correct Answer: A (2) The instrument used to measure the purity of milk is (Pg 149;Q 2) (A) Barometer (B) Hygrometer (C) Lactometer (D) Speedometer Correct Answer: C SESSION 1. INTRODUCTION, DENSITY AND RELATIVE DENSITY 265

(3) The density of water at 25°C is (Pg 149;Q 6) (A) 1g/cm3 (B) 2g/cm3 (C) 3g/cm3 (D) 0.99g/cm3 Correct Answer: D SESSION 1. INTRODUCTION, DENSITY AND RELATIVE DENSITY 266

SESSION 2 WHEN DO OBJECTS FLOAT ON WATER AND ATMOSPHERIC PRESSURE 2.1 Mind Map SESSION 2. WHEN DO OBJECTS FLOAT ON WATER AND ATMOSPHERIC ... 267

SESSION 2. WHEN DO OBJECTS FLOAT ON WATER AND ATMOSPHERIC ... 268

2.2 Terminology i. Atmospheric pressure –The pressure exerted by the atmosphere. ii. Barometer –The device to measure atmospheric pressure. 2.3 Key Concepts i. On all the objects floating in liquids an upward force called force of ‘buoyancy’ acts. ii. An object immersed in a fluid appears to have lost some weight. iii. This apparent loss of weight of an object immersed in a liquid is equal to the weight of displaced liquid. This is known as Archimedes’ principle. iv. When an object floats on the surface of a liquid, it displaces liquid having weight equal to its own weight. v. Force acting on unit area of the surface of an object is called pressure. vi. Atmospheric pressure = ρhg, where h = height of atmosphere, ρ= average density of atmosphere, g = acceleration due to gravity. vii. The pressure exerted by a liquid increases with depth below the surface of liquid. 2.4 Reflection on Concepts Q1. [AS1] Why do some objects float on water and some sink? [Refer to TB page 148 Q1] A. Floating or sinking of objects on water depends on two factors. a. Relative density. b. Weight of the water displace by the object. If the relative density of an object is greater than 1, the object sinks otherwise it floats. Even though the relative density is greater than 1, if the weight of the water displaced by the object equal to the weight of the object itself, the object floats on the water. Q2. [AS5] Draw the diagram of a mercury barometer. [Refer to TB page 148 Q5] SESSION 2. WHEN DO OBJECTS FLOAT ON WATER AND ATMOSPHERIC ... 269

A. 2.5 Application of Concepts Q1. [AS1] An ice cube floats on the surface of water filled in glass tumbler (density of ice = 0.9 g/cm3 ). Will the water level in the glass rise when the ice melts completely? [Refer to TB page 148 Q3] A. No. The level of water does not raise as the volume of the water ice mixture remains same when the ice melts. Q2. [AS1] Find the pressure at a depth of 10 m in water if the atmospheric pressure is 100 kPa. [1 Pa = 1 N/m2 ] [100 kPa = 105 Pa = 105 N/m2 = 1 atm] [Refer to TB page 148 Q4] A. Depth 'h' = 10 m; Atmospheric Pressure = 100 kPa Density of water = 1kg/m3 Pressure at depth 'h' is P = Atmospheric pressure + hρg = 100 + 10 x 1 x 9.8 = 100 + 98 = 198 kPa SESSION 2. WHEN DO OBJECTS FLOAT ON WATER AND ATMOSPHERIC ... 270

SESSION 3 MEASURING THE FORCE OF BUOYANCY 3.1 Mind Map 3.2 Terminology i. Buoyancy –The upward force that a fluid exerts on an object less denser than itself. 3.3 Key Concepts i. The pressure exerted by a liquid increases with depth below the surface of liquid. ii. Pascal’s principle: It states that the external pressure applied to an enclosed volume of fluid is transmitted equally in all directions throughout the volume of the fluid. SESSION 3. MEASURING THE FORCE OF BUOYANCY 271

3.4 Reflection on Concepts Q1. [AS1] Explain buoyancy in your own words. [Refer to TB page 148 Q3] A. i. When an object is kept in a fluid, it experiences an upward force. ii. Substances thus appear lighter when immersed completely or partially in a liquid. iii. The tendency of a fluid to exert an upward force on the object wholly or partially im- mersed in it is called buoyancy. The upward force that acts on the object immersed in a fluid is called buoyant force. 3.5 Application of Concepts Q1. [AS6] How can you appreciate the technology of making ships float, using the material which sink in water. [Refer to TB page 148 Q5] A. Archimedes solved a problem: He noticed that as he lowered himself into the bath, the water displaced by his body overflowed the sides and he realized that there was a relationship between his weight and the volume of water displaced. This helped him solve the problem given to him by the king, as to whether his crown was made of pure gold or partly silver. Archimedes reasoned that if the crown had any silver in it, it would take up more space than a pure gold crown of the same weight because silver is not as dense as gold. He compared the crown’s volume with the volume of equal weights of gold and then silver, he found the answer that the crown was not pure gold. The Buoyancy Principle: Archimedes continued to do more experiments and came up with a buoyancy principle, that a ship will float when the weight of the water it displaces equals the weight of the ship and anything will float if it is shaped to displace its own weight of water before it reaches the point where it will submerge. It involves very sharp scientific calculations and engineering technologies. Really such type of technologies are highly appreciable. 3.6 Higher Order Thinking Skills Q1. [AS3] Can you make iron to float on water? How? [Refer to TB page 148 Q1] A. Any object will float on water as long as the mass of the water it displaces is more than or equal to the mass of the object. Objects built using materials that are more dense than water can still be made to float by making them hollow like a boat. SESSION 3. MEASURING THE FORCE OF BUOYANCY 272

Q2. [AS7] Where do you observe Archimedes’ principle in our daily life? Give two examples. [Refer to TB page 148 Q2] A. i) Construction of ships ii) Hot air balloons 3.7 Suggested Experiments Q1. [AS3] Conduct an experiment to understand the phenomenon that a stone immersed in water loses its weight. Write a report on it. [Refer to TB page 149 Q2] A. Suspend a stone from a spring balance. (It is better to take a stone that is more than 300 g). Note the reading on the spring balance. The reading gives the weight of the stone. Take an overflow vessel with water and place a graduated beaker below the beak asshown in the given figure. SESSION 3. MEASURING THE FORCE OF BUOYANCY 273

Now immerse the stone in the water. Note the reading on the spring balance and measure the volume of water that overflows into the graduated beaker. Observation : The reading of the spring balance gives the weight of the immersed stone and the beaker reading gives the volume of water displaced by the stone as shown in the figure. Conclusion : The apparent loss of weight of the immersed stone is equal to the weight of water displaced by the stone i.e., equal to the force of buoyancy exerted by the water. This wonderful observation was made by Archimedes, an ancient Greek scientist. 3.8 Suggested Projects Q1. [AS4] The oil brakes in vehicles works on the Pascal’s principle. Collect the information regarding the working of air brakes in vehicles and write a report. [Refer to TB page 149 Q1] A. Students’ activity. SESSION 3. MEASURING THE FORCE OF BUOYANCY 274

Objective Questions (1) If Po = Pressure, n = Density, h= Height, and g = Gravitational constant then the atmospheric pressure ( Pg 149; TB Q 3) (A) Po = nhg (B) P = mgh (C)P = vgh (D) P= 1 mgh 2 Correct Answer: A (2) The first barometer with mercury was invented by (Pg 149; Q 4) (A) Pascal (B) Archimedes (C) Newton (D) Torricelli Correct Answer: D (3) The hydraulic jacks/lifts which is used in automobile work shops, works on the principle of (Pg 149;Q 5) (A) Archimedes (B) Pascal (C) Torricelli (D) Newton Correct Answer: B —— CCE Based Practice Questions —— AS1-Conceptual Understanding Very Short Answer Type Questions 1. State true or false. [Refer to Session 8.1 ] (i) Milk is denser than water. [] (ii) If we throw a glass marble and a wooden block in water, the wooden block sinks as it has higher density than water. [] CHAPTER 8. FLOATING BODIES 275

(iii) The relative density of a substance is the ratio of the density of the substance to the density of water. [] (iv) We cannot use hydrometer to find the density of any liquid. [ ] (v) Value of density of water in C. G. S system is 1 g/cm3. [ ] 2. Match the following. Column B [(Session 8.1)] Column A i. Density [] a. = Density of an object Density of water ii. Relative density of an object [ ] b. = Mass Volume iii. Relative density of a liquid [] c. = kg iv. Unit of density [] m3 d. = 1 (ρ1 + ρ2 ) 2 v. Effective density of the mixture [ ] e. = Weight of the liquid Weight of the same volume of water 3. State true or false. [ ] [Refer to Session 8.3 ] [ ] [ ] (i) The density of salt water is greater than that of fresh water. [ ] (ii) Hydraulic brakes are used in cars. (iii) Hydraulic jacks are used for lifting automobiles in workshops. (iv) We cannot use Archimedes’ principle in construction of ships. CHAPTER 8. FLOATING BODIES 276

(v) Any object, wholly or partly immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by it. [] 4. Match the following. Column B [(Session 8.3)] [ ] a. Lactometer Column A i. Bramah press ii. Density of mercury in S.I. system [ ] b. Barometer iii. Instrument used to measure [ ] c. 13.6 x 103 kg/m3 atmospheric pressure iv. Instrument used to measure purity [ ] d. Hydraulic jack of milk v. Device used to lift a car [ ] e. Application of Pascal’s principle 5. Fill in the blanks. [Refer to Session 8.3 ] (i) Apparent loss of weight must be equal to the ___________________________ . (ii) used buoyancy principle to know the purity of gold crown. (iii) A hydraulic jack’s functioning is described very accurately by principle. (iv) If is applied to an enclosed volume of fluid, it is transmitted equally in all directions throughout the fluid volume. 6. State true or false. [Refer to Session 8.2 ] (i) The pressure exerted by a liquid increases with depth below the surface of liquid. [] CHAPTER 8. FLOATING BODIES 277

(ii) Pressure is the thrust per unit area of a surface. [] (iii) An object immersed in a fluid appears to have gained some weight. ] [ (iv) The density of salt water is lesser than that of fresh water. [ ] (v) Certain objects float on water because their density is less than the density of water. [] Short Answer Type Questions 7. Answer the following questions in 3-4 sentences. (i) [(Session 8.1)] How is the relative density of liquids obtained? (ii) [(Session 8.1)] Write the formulae for: i) Density, ii) Relative density of an object, and iii) Relative density of a liquid. CHAPTER 8. FLOATING BODIES 278

(iii) [(Session 8.1)] A ball has a radius of 4 cm and mass of 1 kg. What is the density of the ball? 8. Answer the following questions in 3-4 sentences. (i) [(Session 8.3)] State Archimedes’ principle. CHAPTER 8. FLOATING BODIES 279

(ii) [(Session 8.3)] How do hydraulic pumps work? 9. Answer the following questions in 3-4 sentences. (i) [(Session 8.2)] Define 1 Pascal. (ii) [(Session 8.2)] What happens if we place a block of wood in kerosene oil? Explain the observation. CHAPTER 8. FLOATING BODIES 280

(iii) [(Session 8.2)] A dead body floats on water with its head immersed in water. Explain. Long Answer Type Questions 10. Answer the following questions in 6-8 sentences. (i) [(Session 8.3)] What do you mean by buoyancy? In which direction does the buoyant force acts on an object immersed in a liquid act? CHAPTER 8. FLOATING BODIES 281

11. Answer the following questions in 6-8 sentences. (i) [(Session 8.2)] What happens if we use any liquid other than mercury in a barometer? AS2-Asking questions and making hypothesis Short Answer Type Questions 12. Answer the following questions in 3-4 sentences. (i) [(Session 8.1)] Find out the effective density of a mixture of water and milk when they are taken in equal volumes. CHAPTER 8. FLOATING BODIES 282

AS3-Experimentation and field investigation Short Answer Type Questions 13. Answer the following questions in 3-4 sentences. (i) [(Session 8.1)] An oil bottle weighs 30 g. After removing the oil, the bottle weighed 10 g. When it is filled with water the bottle weighs 28 g. Now find the density of oil. (ii) [(Session 8.1)] What is a lactometer? Draw the diagram of an improvised lactometer. Name any two similar instruments which can be used to find the density of any liquid. 14. Answer the following questions in 3-4 sentences. 283 (i) [(Session 8.3)] List the factors affecting buoyant force. CHAPTER 8. FLOATING BODIES

Long Answer Type Questions 15. Answer the following questions in 6-8 sentences. (i) [(Session 8.2)] Describe a simple activity to show that a body loses weight when immersed in a fluid. CHAPTER 8. FLOATING BODIES 284

AS4-Information skills and projects Long Answer Type Questions 16. Answer the following questions in 6-8 sentences. (i) [(Session 8.1)] The densities of some substances are given: Substance Density (kg/m3 ) Lead 11,500 Aluminium 2700 Water 1000 Gold 19300 Mercury 13600 Iron 8000 Answer the following questions: a) Arrange the substances in the increasing order of their relative densities. b) What will be the mass of lead brick with dimensions of 5 cm x 10 cm x 20 cm? c) What is the relative density of aluminium? d) If the mass of iron block is 640 kg, find the volume of iron. CHAPTER 8. FLOATING BODIES 285

AS5-Communication through drawing and model making Short Answer Type Questions 17. Answer the following question. (i) [(Session 8.2)] Draw the image of a barometer. AS6-Appreciation and aesthetic sense, Values Short Answer Type Questions 18. Answer the following questions in 3-4 sentences. (i) [(Session 8.2)] Why do we use hydrometer and barometer? CHAPTER 8. FLOATING BODIES 286

AS7-Application to daily life, concern to bio diversity Short Answer Type Questions 19. Answer the following questions in 3-4 sentences. (i) [(Session 8.3)] It is easier for a man to swim in sea water than in river water. Why? CHAPTER 8. FLOATING BODIES 287

Objective Questions (B) iron nail AS1-Conceptual Understanding (D)copper plate 20. Choose the correct answer. (i) An object that floats on water is (A) cork (C)rupee coin (ii) Buoyant force depends on (B) density of liquid (A) weight of fluid displaced (D)all of these (C)accleration due to gravity (iii) By the condition of floatation, if d1 and d2 are the densities of liquids in which a hydrometer sinks to depths of h1 and h2 respectively, which of the following is true? (A) d1 = h1 d2 h2 (B) d1 = h2 d2 h1 (C)d1 h2 = d2 h1 (D)None of the above (iv) Loss in weight is more in (A) salted water (B) tap water (C)same in both (D)double in salt water than tap water CHAPTER 8. FLOATING BODIES 288

(v) The upward force applied on an object immersed in a liquid is called (A) friction (B) atmospheric pressure (C) buoyancy (D)repulsive force (vi) A balloon filled with hydrogen gas rises up into the air due to the (A) weight of the balloon (B) low density of the air (C)high density of the air (D)buoyant force exerted on it by air (vii) Atmospheric pressure in terms of height of mercury column (in cm) is (A) 76 (B) 67 (C) 760 (D) 7.6 (viii) Which of the following principle says that weight of liquid displaced and upthrust are equal? (A) Pascal’s principle (B) Faraday’s principle (C)Archimedes’ principle (D)Charles’s principle (ix) Unit of pressure in the S.I. system is (B) Pascal (A) Torricelli (C) Henry (D) Ampere (x) Bramah press applies __________ principle. (A) Pascal’s (B) Faraday’s (C) Archimedes’ (D) Charles’s CHAPTER 8. FLOATING BODIES 289

(xi) The correct increasing order of relative densities is: (A) Air >water >iron (B) Water >iron >air (C)Water >iron <air (D)Air <water <iron (xii) The principle on which the hydrometer works is (A) Bernoulli’s principle (B) Pascal’s principle (C)Archimedes’ principle (D)Buoyancy principle (xiii) ’ρ ’ in the formula for calculating the pressure difference between two levels in a liquid denotes (A) pressure (B) volume (C)relative density (D) density AS3-Experimentation and field investigation 21. Choose the correct answer. (i) _____________ is used to determine the purity of a sample of milk. (A) Barometer (B) Lactometer (C) Thermometer (D) Hygrometer AS4-Information skills and projects (B) 13.6 × 103kg/m3 (D) 13.6kg/cc 22. Choose the correct answer. (i) Density of mercury in SI system is (A) 13.6 × 102gram/cc (C)13.6 × 102gram/cc CHAPTER 8. FLOATING BODIES 290

AS6-Appreciation and aesthetic sense, Values 23. Choose the correct answer. (i) Scientist who gave the principle about what happens when an external pressure is applied to an enclosed liquid is (A) Newton (B) Galileo (C) Pascal (D) Einstein CHAPTER 8. FLOATING BODIES 291

9. WHAT IS INSIDE THE ATOM? SESSION 1 INTRODUCTION AND SUBATOMIC PARTICLES 1.1 Mind Map 1.2 Terminology i. Atom – An atom is the smallest particle of an element that can participate in chemical reactions and retain all its properties. ii. Sub atomic particle –Experimental evidence showed that atoms were divisible and are made up off small particles. These particles are smaller than the atom and are present inside an atom.These are called sub atomic particles. Protons, neutrons and electrons are called sub atomic particles. iii. Electron – An electron is a negatively charged subatomic particle. It can be either free (not attached to any atom), or bound to the nucleus of an atom. iv. Proton – The proton is a subatomic particle with a positive electric charge and mass slightly less than that of a neutron. SESSION 1. INTRODUCTION AND SUBATOMIC PARTICLES 292

v. Neutron – The neutron is a subatomic particle, symbol 'n' or 'no', with no net electric charge and a mass slightly larger than that of a proton. 1.3 Key Concepts i. John Dalton’s notions that atoms are indivisible have raised some doubts and left opens for further probing. ii. Michael Faraday discovered that atoms were getting negative charge during electrol- ysis. iii. Later three different sub–atomic particles were discovered. They are (i) electrons (ii) protons and (iii) neutrons. iv. Electron was discovered by J.J. Thomson and James Chadwick discovered neutron. v. The sub atomic particle with negative charge is called electron. vi. Proton (p) is the positively charged sub–atomic particle. vii. Neutrons are the particles in an atom that have a neutral charge. 1.4 Reflection on Concepts Q1. [AS1] What are the three sub atomic particles? [Refer to TB page 164 Q1] A. The three subatomic particles are (1) Electrons, (2) Protons and, (3) Neutrons. Objective Questions (B) Chadwick (1) Electron was invented by (Pg 165, Q 1) (A) Thomson (C) Goldstein (D) Stoney (B) Rutherford Correct Answer: A (2) Proton was invented by (Pg 165; Q 2) (A) Thomson (C) Goldstein (D) Stoney Correct Answer: B SESSION 1. INTRODUCTION AND SUBATOMIC PARTICLES 293

(3) Neutron was invented by (Pg 165; Q 3) (A) Thomson (B) Chadwick (C) Goldstein (D) Stoney Correct Answer: B (4) Alpha particles are made up of the following primary particles (Pg 165; Q4) (A) 2 Protons and 2 Neutrons (B) 2 Protons and 2 Electrons (C)2 Neutrons and 2 Positrons (D) 2 Protons and 2 Neutrinos Correct Answer: A SESSION 1. INTRODUCTION AND SUBATOMIC PARTICLES 294

SESSION 2 STRUCTURE OF AN ATOM 2.1 Mind Map 2.2 Terminology i. Nucleus – The nucleus is the small, dense region consisting of protons and neutrons at the center of an atom. ii. Atomic mass – The number of times one atom of a given element is heavier than 1/12th part of mass of carbon –12 atom is called its atomic mass. iii. 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 2. STRUCTURE OF AN ATOM 295

iv. 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. 2.3 Key Concepts i. Thomson determined that atoms contain negatively charged particles, which are named as electrons. He proposed a model of an atom that shows how electrons are dis- tributed throughout the positively charged material. ii. Rutherford’s alpha particle scattering experiment led to the discovery of the atomic nucleus. iii. Rutherford suggested updated model of the atom. He proved that most of the atom is empty with small dense, positively charged nucleus in the centre. His continued work, as well as that of others, eventually led to identification of the proton and neutron in the nucleus. But the stability of the atom could not be explained by Rutherford’s model. iv. Neils Bohr’s model of the atom was more successful. He suggested that electrons revolved in fixed orbits or shells or energy levels around the nucleus. v. Shells of the atom are designated as K, L, M, N. 2.4 Reflection on Concepts Q1. [AS1] What were the three major observations Rutherford made in his gold foil experi- ment? [Refer to TB page 164 Q2] A. The three major observations that Rutherford made in his gold foil experiment are – • Most of the space inside the atom is empty. • Atom has a dense, heavy, positively charged central part called nucleus. • The electrons are located at a distant from the nucleus. The negatively charged electrons revolve around the nucleus in well defined orbits. • The size of the nucleus is very small as compared to the size of the atom. Q2. [AS1] Give the main postulates of Bohr’s model of an atom. [Refer to TB page 164 Q3] A. The main postulates of Bohr’s model of an atom are – SESSION 2. STRUCTURE OF AN ATOM 296

• The electrons revolve around the nucleus in certain, discrete circular orbits of the atom. These orbits or shells are called energy levels. • While revolving in these discrete orbits the electrons do not radiate energy and this helps electrons not to fall into the nucleus. • These orbits or shells are represented by the letters K, L, M, N. . . or the num- bers, n= 1, 2, 3, 4. . . 2.5 Application of Concepts Q1. [AS1] What are the limitations of J.J. Thomson’s model of the atom? [Refer to TB page 164 Q2] A. • Thomson’s model of an atom could not explain stability of the atom. • It could not explain hydrogen spectrum. • His proposition that the positive charges (protons) in which negatively charged electrons are embedded is found to be irrelevant. • The main limitation of J.J Thomson’s model was, he was unable to explain, how the positively charged particles are shielded from negatively charged particles without getting neutralized. Q2. [AS1] Compare the sub –atomic particles electrons, protons and neutrons. [Refer to TB page 164 Q1] SESSION 2. STRUCTURE OF AN ATOM 297

A. Electrons Protons Neutrons 1. Electrons are 1. Protons are 1. Neutrons are negatively charged positively uncharged particles particles of an charged particles of an atom. atom. of an atom. Neutrons are neutral. 2. It has mass of 2. It has a mass 2. The mass of 9.1 × 10−28g. of 1.673 × 10−24g. neutron is 1.675 × 10−24g. 3. Revolves in an 3. Present in the 3. Present in the orbit around the nucleus nucleus of an atom. nucleus of the of an atom. atom. 4. Mass of electron 4. Mass of 4. Almost equal to is negligible proton is that of the mass of compared to the 1836 times a proton. mass of a proton. heavier than the mass of electron. Q3. [AS5] Sketch Rutherford’s atomic model. Why Rutherford’s model of an atom is called the planetary model? [Refer to TB page 164 Q7] SESSION 2. STRUCTURE OF AN ATOM 298