202110241-TRIUMPH-STUDENT-WORKBOOK-PHYSICAL_SCIENCE-G08-PART1

Observation : SAMPLE DOES THE BULB Iron GLOW(YES/NO) Zinc Yes Copper Sulphur Yes Aluminium Carbon Yes Magnesium Iodine Yes Yes No Yes No Conclusion: Metals are good conductors of electricity and non metals are poor con- ductors of electricity. Objective Questions (1) The property of changing the metals into sheets is __________.(Pg 64; TB Q 5) (A) Malleability (B) Ductility (C)Conductivity of heat (D)Electric Conductivity Correct Answer: A SESSION 1. INTRODUCTION AND PHYSICAL PROPERTIES OF METALS ... 99

SESSION 2 CHEMICAL PROPERTIES 2.1 Mind Map 2.2 Terminology i. Rusting – A chemical process that takes place in metals when exposed to oxygen present in the atmosphere forming a metal oxide. It is common in iron metal. ii. Displacement reaction – Displacement reaction is a chemical reaction in which a more reactive element displaces a less reactive element from its compound. iii. Vigorous reaction – When a piece of sodium floats on the surface of water, it produces a ‘hissing’ sound. This shows that sodium is reacting extremely fast or vigorously with water. 2.3 Key Concepts i. Metals react with oxygen to produce metal oxides. 100 ii. Metal oxides are basic in nature and non–metallic oxides are acidic. iii. Some metals react with water and produce hydrogen gas. iv. Metals react with acids and produce salts and hydrogen gas. SESSION 2. CHEMICAL PROPERTIES

v. Some metals react with bases to produce hydrogen gas. vi. More reactive metals displace less reactive metals from their compounds. 2.4 Reflection on Concepts Q1. [AS1] Which gas makes a ‘pop’ sound if exposed to a lit matchstick? [Refer to TB page 63 Q5] A. Hydrogen gas makes a pop sound when exposed to a lit matchstick. It is the sound of hydrogen burning in air to give water. 2.5 Higher Order Thinking Skills Q1. [AS1] In a chemical reaction iron is unable to displace zinc from zinc sulphate.Why? [Refer to TB page 64 Q3] A. Iron cannot displace zinc from zinc sulphate, because iron is less reactive than zinc. A less reactive metal cannot displace a more reactive metal from its solution/compound. 2.6 Suggested Experiments Q1. [AS3] Conduct an experiment to know the reaction of Oxygen with metals and non met- als. [Refer to TB page 64 Q1] A. AIM: To know the reaction of oxygen with metals and non metals. MATERIALS REQUIRED: One metal sample (magnesium) and one non metal sample (sulphur), spirit lamp or Bunsen burner and litmus paper. PROCEDURE: i. Take a small strip of magnesium and note its appearance. Burn it and note the appearance after burning. ii. Collect the ashes of magnesium in a test tube and add some distilled water to it. Test the solution with red and blue litmus paper. Note the colour change in table below. SESSION 2. CHEMICAL PROPERTIES 101

iii. Take a small amount of powdered sulphur in a deflagrating spoon and heat it.(You can make your own spoon using a metal bottle cap and wrap a metal wire around it.) iv. As the sulphur starts burning, introduce the spoon into a gas jar/tumbler. v. Cover the tumbler with a lid to ensure that the gas produced does not escape. vi. Remove the spoon after some time but try to keep the jar covered. vii. Add a small amount of water into the tumbler and quickly replace the lid. viii. Shake the solution well and check the solution with red and blue litmus paper. Sample Appearance Appearance Effect on before reaction after reaction litmus paper Magnesium Shiny silver White powder Red litmus turned to blue metal Sulphur Yellowish brown Colourless gas Blue litmus powdery turned to red substance SESSION 2. CHEMICAL PROPERTIES 102

When the samples are burnt, they react with oxygen in air to give different products. Magnesium+Oxygen → Magnesium oxide (s) (g) (s) Sulphur + Oxygen → Sulphur dioxide (s) (g) (g) All the products in the above reactions are oxides. We also infer that non- metals re- act with oxygen to give oxides which are acidic, while metals react with oxygen to give oxides that are basic in nature. Q2. [AS3] The nature of oxides helps to identify the metals and non metals. Conduct an experiment to prove this and record the observations. [Refer to TB page 64 Q2] A. Metals react with oxygen and give basic oxides. Generally these basic oxides dissolve in water to form bases, which turn red litmus to blue. E.g.: Magnesium burns in air to form magnesium oxide. It dissolves in water and forms magnesium hydroxide. 2Mg + O2 → 2MgO MgO + H2 O → Mg(OH)2 Non–metals react with oxygen and form their oxides. These oxides dissolve in water to form acids, which turn blue litmus to red. E.g.: Sulphur (S) + Oxygen(O2 ) → Sulphur dioxide (SO2 ) SO2 + H2 O → H2 SO3 (Sulphurous acid) The following experiment can be conducted to find the nature of oxides of metals and non–metals: AIM: To know the nature of oxides of metals and non metals. MATERIALS REQUIRED: One metal sample (magnesium) and one non metal sam- ple(sulphur), spirit lamp or Bunsen burner and litmus paper. SESSION 2. CHEMICAL PROPERTIES 103

PROCEDURE: i. Take a small strip of magnesium and note its appearance. Burn it and note the appearance after burning. ii. Collect the ashes of magnesium in a test tube and add some distilled water to it. Test the solution with red and blue litmus paper. Note the colour change in table below. iii. Take a small amount of powdered sulphur in a deflagrating spoon and heat it.(You can make your own spoon using a metal bottle cap and wrap a metal wire around it.) iv. As the sulphur starts burning, introduce the spoon into a gas jar/tumbler. v. Cover the tumbler with a lid to ensure that the gas produced does not escape. vi. Remove the spoon after some time but try to keep the jar covered. vii. Add a small amount of water into the tumbler and quickly replace the lid. viii. Shake the solution well and check the solution with red and blue litmus paper. Sample Appearance Appearance Effect on before reaction after reaction litmus paper Magnesium Shiny silver White powder Red litmus turned to blue metal Sulphur Yellowish brown Black in colour Blue litmus powdery turned to red substance SESSION 2. CHEMICAL PROPERTIES 104

This experiment shows us that the oxides of metals are basic and that the oxides of non–metals are acidic in nature. Objective Questions .( Pg 64; TB Q1) (1) Sulphur dioxide is a (A) Basic oxide (B) Acidic oxide (C) Neutral oxide (D) Dual natural oxide Correct Answer: B (2) Some metals react with acids to evolve gas. (Pg 64; TB Q 3) (A) Hydrogen (B) Oxygen (C)Carbon dioxide (D) Nitrogen Correct Answer: A (3) Generally non metallic oxides are in nature.( Pg 64; TB Q 4) (A) Basic (B) Acidic (C) Neutral (D)Dual nature Correct Answer: B SESSION 2. CHEMICAL PROPERTIES 105

SESSION 3 USES OF METALS AND NON-METALS 3.1 Mind Map SESSION 3. USES OF METALS AND NON-METALS 106

3.2 Terminology i. Sulphur – It is a non–metal used in making fireworks, crackers, gun powder, matchsticks and antiseptic ointments. ii. Activated Carbon – Activated carbon is used as a decolourising agent and also in water purification systems. iii. Tincture of iodine – It is used for medical purposes. iv. Currency coins – Currency coins are made from aluminium and copper mixture. 3.3 Key Concepts i. Metals and non–metals are widely used in our life. ii. Sulphur is used in making fireworks, crackers, gun powder, matchsticks and antiseptic ointments. It is found in onions, garlic, eggs, hair and nails. iii. Activated carbon is used as a decolourising agent and also in water purification systems. iv. Tincture of iodine is used for medical purposes. v. Thin aluminium foil is used in the inner packing of food materials and toffees. vi. Aluminium and copper mixture is used in currency coins, medals and statues. vii. A zinc and iron mixture is used in the making of iron sheets. viii. Most agricultural instruments are made of iron. ix. Electrical appliances, automobiles, satellites, aeroplanes, cooking utensils, machinery, decorative materials etc. are made of metals due to their malleability, ductility and low weight. 3.4 Higher Order Thinking Skills Q1. [AS6] How do you appreciate the wide range utility of aluminium right from utensils to spacecraft? [Refer to TB page 64 Q4] A. Aluminium is the third most abundant element in the earth’s crust and it is cheap. It is used to make cooking utensils. The foil of aluminium is used in packing food material and medicines. Aluminium alloys are light and strong. They are used to make bodies of cars and aircrafts. Q2. [AS7] Dumping of waste materials made up of metals and non–metals leads to envi- ronment pollution. Do you support the statement? Give your justification with suitable examples. [Refer to TB page 64 Q2] SESSION 3. USES OF METALS AND NON-METALS 107

A. The unused or unserviceable materials made up of metals and non–metals that are dumped by us leads to environmental pollution because these are non–biodegradable. The worn out machines and machine parts, cycles (vehicles), electronic wastes etc.,are all non–biodegradable. Non–metals are also causing environmental problems.This is leading to over exploitation of natural resources causing pollution in the surroundings. This dumping of wastes is also disturbing the natural habitat of many organisms and leading to imbalance and variations in biodiversity. 3.5 Suggested Projects Q1. [AS2] Imagine the human life without metals, write a report. [Refer to TB page 64 Q2] A. Students’ activity. Hint –Metals are widely used in our daily life. All the machinery and their parts are made up of metals. Transport systems, factories, utensils, and spacecrafts all are made up of metals. Hence life without metals would be very difficult. Zinc, copper, magnesium, manganese are important nutrients needed for our growth. No vehicles and no transport would be possible without metals. Aluminium and Tin are used to make packing of food materials. The copper wires, zinc plates etc. are necessary for the production of electricity. Q2. [AS4] Collect the information about metals which we use in our daily life, and their uses. Write a report on it. [Refer to TB page 64 Q1] A. Students’ activity. An answer is given as a reference. USES OF METALS IN DAILY LIFE 1. In electronics: Electronics are the equipment which largely rely on electricity to function. We use many electronics like TV, mobiles, fridges etc. in daily life. These electronics use metals in the body for different purposes. But one of the key purpose is to facilitate electricity transfer. Since metals are good conductors, metals like copper, lead are widely used. May be without metals, electronics would have not been progressed so much. SESSION 3. USES OF METALS AND NON-METALS 108

2. In medicine : Metals are available as micro–elements in our body. They are needed for conduction of nerve impulses, to carry oxygen by blood, to facilitate enzyme reactions and more. So metals are used in medicine to cure any metal deficiency diseases in humans and animals. Besides, metals like titanium, aluminum, magnesium are widely used in medicine for roles like antacids. They are specially studied under the subject of inorganic chemistry. 3. In building construction: Metals like iron and steel are widely used in building and home constructions. Their strength and ability to withstand heavy weights make them preferred in construction. They are commonly used in reinforced concrete roofing, pillars, foundations, fencing etc. 4. In jewellery: Metals like Gold, silver, platinum, copper are widely used in jewellery. 5. In machinery & automobiles : Many machines and automobiles are made of metals extensively. Metals which can withstand high temperature and pressure during work are preferred. The commonly used metal is iron, steel, aluminum etc. 6. In farming. Farming requires many metal tools for tilling the soil, cutting, sowing the seeds etc. So most of the farming equipment are made of metals like iron, steel etc. They can be used in both wet and dry conditions as required by farming. 7. In cooking: Utensils are best made from metals like steel, aluminum and copper. Stoves, furnaces, bowels, troughs, spoons, knives used in kitchen are made from metal. 8. Furniture: Even some home furniture are made of metal instead of wood. Fans, stands, cupboards, drawers are mostly made from metal. 9. Security systems: Metals play an important role in security systems. Metals are used in making locks, lockers, safes, cupboards to store valuable items. Objective Questions (1) Maximum metals are obtained in state.(Pg 64; TB Q 2) (A) Liquid (B) Solid (C) Gaseous (D) Plasma Correct Answer: B SESSION 3. USES OF METALS AND NON-METALS 109

—— CCE Based Practice Questions —— AS1-Conceptual Understanding Column B Very Short Answer Type Questions a. ductility 1. Match the following. [(Session 4.1)] Column A i. Making into thin sheets ii. Shining materials b. sonority iii. Making into wires c. conductivity iv. Transmission of heat d. lustrous v. Making ringing sound e. malleability 2. Fill in the blanks. [Refer to Session 4.3 ] (i) is used in making fire works. (ii) is used as decolourising agent. (iii) is used for medical purposes as an antiseptic. (iv) mixture is used in making currency coins. (v) is used in making of iron sheets. 3. Fill in the blanks. . [Refer to Session 4.2 ] gas. (i) Metals which do not react with air are (ii) Metals react with acids and liberate CHAPTER 4. METALS AND NON–METALS 110

(iii) Oxides of non–metals are usually in nature. (iv) Oxides of metals are usually in nature. (v) Reaction of atmospheric gases and moisture with metal surface is called . Short Answer Type Questions 4. Answer the following questions in 3-4 sentences. (i) [(Session 4.1)] Compare the physical properties of coal and gold. 5. Answer the following questions in 3-4 sentences. (i) [(Session 4.2)] Discuss the reaction of acids with metals and non–metals. CHAPTER 4. METALS AND NON–METALS 111

Long Answer Type Questions 6. Answer the following questions in 6-8 sentences. (i) [(Session 4.1)] Compare the properties of metals and non–metals with respect to i. Malleability ii. Ductility iii. Electrical conductance CHAPTER 4. METALS AND NON–METALS 112

AS2-Asking questions and making hypothesis Short Answer Type Questions 7. Answer the following questions in 3-4 sentences. (i) [(Session 4.1)] Rupali enjoys playing dandiya /garba with two wooden sticks that hit one another. Her friend Shyam joins Rupali with steel sticks. Both the pair of sticks create a rhythmic sound. Rupali concludes that wood is a metal. Do you support Rupali? Mention two points to support your answer. 8. Answer the following questions in 3-4 sentences. (i) [(Session 4.3)] Why are most of the agricultural implements made of metal? Give reasons. CHAPTER 4. METALS AND NON–METALS 113

AS3-Experimentation and field investigation Long Answer Type Questions 9. Answer the following questions in 6-8 sentences. (i) [(Session 4.2)] In an experiment to study the reaction of metals and non metals with water, write the following – a ) Aim b) Apparatus c) Procedure d) Observation e) Precaution f) Conclusion CHAPTER 4. METALS AND NON–METALS 114

AS4-Information skills and projects Very Short Answer Type Questions 10. Answer the following questions in one sentence. [Refer to Session 4.1 ] (i) Complete the table. Property Gold Carbon Colour Yellow Malleability Not malleable CHAPTER 4. METALS AND NON–METALS 115

11. Answer the following questions in one sentence. [Refer to Session 4.2 ] (i) Complete the table. Sample Appearance before Appearance after Magnesium tohxeygreeanction with othxeygreeanction with Sulphur Silver white sheet Colourless gas Long Answer Type Questions 12. Answer the following questions in 6-8 sentences. (i) [(Session 4.1)] Study the information given in the following table and write the answers for the following questions. i. The allotrope of carbon which is lustrous – . ii. The allotrope of carbon which conducts electricity – . . iii. The metals which are not ductile at room temperature – iv. The metal which is not sonorous – . CHAPTER 4. METALS AND NON–METALS 116

Material Metal/ Allotrope Lustrous Sonorous Conducts Ductility Sample Non- of electricity Yes Carbon metal Silver Metal No Yes Yes Good conductor Mercury Metal No Yes No Yes No (at all tempera- tures) Zinc Metal No Yes No Yes No (at room tempera- ture) Lead Metal No Yes No Poor Yes conductor Graphite Non– Yes Yes No Yes No (at all metal tempera- tures) CHAPTER 4. METALS AND NON–METALS 117

AS5-Communication through drawing and model making Short Answer Type Questions 13. Answer the following questions in 3-4 sentences. (i) [(Session 4.1)] Observe the diagram and write why is the arrangement done. Long Answer Type Questions 14. Answer the following question. (i) [(Session 4.1)] Draw the circuit diagram to show the electrical conductivity of a mate- rial. CHAPTER 4. METALS AND NON–METALS 118

AS6-Appreciation and aesthetic sense, Values Short Answer Type Questions 15. Answer the following questions in 3-4 sentences. (i) [(Session 4.3)] Write any four uses of metals. CHAPTER 4. METALS AND NON–METALS 119

AS7-Application to daily life, concern to bio diversity Short Answer Type Questions 16. Answer the following questions in 3-4 sentences. (i) [(Session 4.3)] In what way the malleability used in our daily life? Long Answer Type Questions 17. Answer the following questions in 6-8 sentences. (i) [(Session 4.3)] Suhani participated in an exhibition and had a stall for fashion acces- sories like necklaces, bangles and earrings. She wants to know the details of each type of accessory that she has in her stall. She decided to make a tabular format. Help her to complete the table below. Material Heavy/ Affected Shine Cost (Cheap / used light in by atmo- (Yes / No) expensive / very weight spheric conditions expensive) (Yes / No) Silver Gold Copper Steel CHAPTER 4. METALS AND NON–METALS 120

Objective Questions AS1-Conceptual Understanding 18. Choose the correct answer. (i) What is the property to have a bright surface and reflect light called? (A) Reflection (B) Refraction (C) Lustrous (D) Metallic (ii) Most of the human body is made of . (A) carbon (B) phosphorus (C) calcium (D) water AS2-Asking questions and making hypothesis 19. Choose the correct answer. (i) Which of the following metals is not sonorous? (A) Aluminium (B) Mercury (C) Copper (D) Iodine (ii) Which of the following metal is not malleable? (A) Gold (B) Silver (C) Aluminium (D) Mercury (iii) Which of the following fail to show the property of conductivity of heat? (A) Iron (B) Rubber (C) Aluminium (D) Copper AS3-Experimentation and field investigation 20. Choose the correct answer. (i) What is the nature of compound obtained when Magnesium is burnt in air? CHAPTER 4. METALS AND NON–METALS 121

(A) It is basic (B) It is acidic (C)It is neutral (D) No compound is formed AS4-Information skills and projects 21. Choose the correct answer. (i) How many elements make 99% of the mass of the human body ? (A) Six (B) Sixteen (C) Sixty (D)Six hundred (ii) The two metals that do not rust are gold and . (A) iron (B) silver (C) platinum (D) copper AS6-Appreciation and aesthetic sense, Values 22. Choose the correct answer. (i) The property of metals that is appreciable, in the preparation of ringing bell is . (A) lustrous (B) sonorous (C) conductivity (D)none of the above AS7-Application to daily life, concern to bio diversity 23. Choose the correct answer. (i) For what purpose is tincture of iodine used ? (A) Industrial purposes (B) Cleaning purposes (C)Medical purposes (D)Packaging purposes (ii) The non metal found in hair and nails of human body is . (A) carbon (B) sodium (C) sulphur (D) calcium CHAPTER 4. METALS AND NON–METALS 122

SESSION 1 5. SOUND 1.1 Mind Map PRODUCTION OF SOUND SESSION 1. PRODUCTION OF SOUND 123

1.2 Terminology i. Sound – Vibrations that travel through the air or another medium and can be heard when they reach a person’s or animal’s ear. It is also a form of energy. ii. Vibration – The to and fro motion of a body from its mean position is known as one vibration. iii. Vocal cords – Larynx has two muscular ligaments called vocal cords. iv. Musical instruments – A musical instrument is an instrument created or adapted to make musical sounds. v. Larynx or voice box – The voice box or larynx is the portion of the respiratory (breath- ing) tract containing the vocal cords which produce sound. It is located between the pharynx and the trachea. vi. Tympanic Membrane – A thin membrane separating the middle ear from the inner part of the external auditory canal that vibrates in response to sound energy and transmits the resulting mechanical vibrations to the structures of the middle ear—called also eardrum, tympanum. 1.3 Key Concepts i. We hear different types of sounds everyday. ii. Sound is produced by vibrating objects. iii. Human beings produce sound by the vibration of vocal cords. iv. Vibration: An oscillation of the parts of a fluid or an elastic solid or electromagnetic waves whose equilibrium has been disturbed. v. Vocal cords: Human beings are able to produce sound with the help of vocal cords. 1.4 Reflection on Concepts Q1. [AS1] How can you explain that sound has energy. [Refer to TB page 81 Q1] A. Take a plastic bottle and a cell phone. Cut the top of the bottle so that it looks like a glass. Play songs on the mobile phone in high volume and place it in the bottle. Close the mouth of bottle with a balloon using rubber band so that it covers the bottle as shown in the figure and stretch it tightly so as to behave like a diaphragm. Place some sugar crystals or small size of sand particles on the balloon diaphragm and observe the movement of particles.Do the same activity after removing the phone from the bottle. SESSION 1. PRODUCTION OF SOUND 124

We will observe that when there is no cell phone inside the bottle, sand particles on the diaphragm remain stationary. While the cell phone plays songs inside the bottle, the diaphragm vibrates which can be seen through dancing of sand particles. The sound produced by cell phone inside the bottle is responsible for these vibrations. Sound is able to do work (vibration of sand/sugar particles). Hence Sound has energy or sound is a form of energy. 1.5 Application of Concepts Q1. [AS1] Write any three musical instruments that you know and explain how they produce sound. [Refer to TB page 81 Q2] A. Stringed Instruments: Guitar, violin, sitar, etc. In these instruments sound is produced by vibrations of metal strings. Percussion Instruments (Membrane Instruments) : Drum, tabla, mridangam etc. are membrane instruments which have a stretched membrane whose vibrations produce sound. Wind Instruments: Flute, shehnai, etc. Due to vibration of the air column these instru- ments produce sound. Q2. [AS3] “Vibrations in a body produce sound.” How do you prove it? [Refer to TB page 81 Q5] A. Aim: To prove vibrations in a body produce sounds. SESSION 1. PRODUCTION OF SOUND 125

Material required: 1. A steel scale 2. A brick 3. A table Procedure: Take a steel scale and keep it on a table. Keep a brick on the steel scale. Now press the other end of the steel scale. It starts vibrating. Observation: We hear the vibrating sound of the scale. Result: The vibrations of a body produce sound. Q3. [AS5] Draw the figures of three musical instruments in your surroundings. [Refer to TB page 81 Q4] A. Students’ activity. 3 musical instruments are given as a reference – 1. Harmonium SESSION 1. PRODUCTION OF SOUND 126

2. Violin 3. Tabla 1.6 Suggested Projects Q1. [AS4] Collect the photographs of different musical instruments and scrap book. [Refer to TB page 82 Q2] A. Students’ activity. Q2. [AS5] Collect photograph of local musician and exhibit them in your class. Make different musical instruments using local available materials [Refer to TB page 82 Q3] A. Students’ activity. SESSION 1. PRODUCTION OF SOUND 127

Few examples for making instruments with locally available materials are given as a reference: i. Fill a plate with water and let the water settle. Strike the rim of the plate with a spoon. You will observe vibrations due to which sound is produced. ii. Place a hack–saw blade in between table and a brick, press the hack–saw blade and leave it abruptly, you will observe vibrations caused by the movement of blade and sound is produced. iii. Take a rubber band and stretch it on a wooden ruler, pull the rubber band and you will observe the vibrations caused due to movement of rubber band produces sound. Objective Questions (1) The number of vibrations produced per second is known as – (Pg 82; TB Q 2) (A) Frequency (B) Shrillness (C) Vibration limit (D) Decibels Correct Answer: A SESSION 1. PRODUCTION OF SOUND 128

SESSION 2 PROPAGATION OF SOUND 2.1 Mind Map 1. Propagation of sound SESSION 2. PROPAGATION OF SOUND 129

2. The ear enables us to hear sound 2.2 Terminology i. Propagation – The process of spreading to a larger area or greater number. ii. Medium – The intervening substance through which sensory impressions are con- veyed or physical forces are transmitted. iii. Vacuum – A space entirely devoid of matter. (Region of space where nothing is present). iv. Eardrum – The membrane of the middle ear, which vibrates in response to sound waves; the tympanic membrane. v. Middle ear or ear ossicles – The space between the eardrum and the inner ear that contains the three auditory ossicles, which convey vibrations through the oval window to the cochlea. vi. Malleus, Incus, and Stapes – These are the bones present in middle ear. SESSION 2. PROPAGATION OF SOUND 130

2.3 Key Concepts i. Sounds propagate through media like solids, liquids and gases. ii. Sound cannot travel in vacuum. iii. Eardrum vibrates due to the vibrations caused by vibrating objects and leads to sense of hearing. iv. Human beings are able to produce sound with the help of vocal cords. 2.4 Higher Order Thinking Skills Q1. [AS1] What is the effect of humidity on quality of sound propagation? Is there any dif- ference in propagation of sound in air during the summer and winter seasons? Discuss. [Refer to TB page 82 Q1] A. Humidity has a small but measurable effect on speed of sound (causing it to increase by about 0.1%–0.6%). The speed of sound is affected by temperature and humidity. Sound passes through hot air faster than it passes through cold air. Sound travels faster in summer season than in winter season because, with the increase in temperature, speed of sound also increases and in summers temperature is high with respect to the winters. Objective Questions (1) An object which moves to and fro motion from rest known as – (Pg82; TB Q 1) (A) Linear motion (B) Vibration (C)Simple motion (D)Angular motion Correct Answer: B (2) The oval window has the surface area of the eardrum. (Pg 82; TB Q 4) (A) 1/10 (B) 2/10 (C) 2/20 (D) 1/20 Correct Answer: D SESSION 2. PROPAGATION OF SOUND 131

SESSION 3 CHARACTERISTICS OF SOUND AND SOUND POLLUTION 3.1 Mind Map 1. Characteristics of sound SESSION 3. CHARACTERISTICS OF SOUND AND SOUND POLLUTION 132

2. Range of Sounds SESSION 3. CHARACTERISTICS OF SOUND AND SOUND POLLUTION 133

3. Sound pollution 3.2 Terminology i. Loudness – Loudness is the characteristic of a sound that is primarily a psychological correlate of physical strength (amplitude). ii. Pitch – The quality of a sound governed by the rate of vibrations producing it or the shrillness of a sound is known as pitch. iii. Noise – Noise is an irregular combination of sounds that are ‘unpleasant’ to hear. iv. Music – Music is a combination of sounds that are produced in an order and pleasant to hear. v. Audible – The sounds that a normal human being can hear are called audible sounds. vi. Feeble – Lacking in volume, loudness. 3.3 Key Concepts i. Frequency and amplitude are important factors which determine the quality of sound. ii. The maximum displacement of a vibrating body from its mean position is called am- plitude. iii. The intensity of sound is measured in terms of decibels (dB). iv. Frequency of sound determines the shrillness or pitch of the sound. v. Pitch is the property of a musical tone which makes it high or low. vi. The range of frequencies of sounds heard by human beings is known as audible range. vii. Sounds which are pleasant are called musical sounds and the unpleasant are called noises. SESSION 3. CHARACTERISTICS OF SOUND AND SOUND POLLUTION 134

3.4 Reflection on Concepts Q1. [AS1] What is the unit to measure the sound intensity. [Refer to TB page 81 Q2] A. Decibel is the unit for measuring the intensity of sound. It is denoted as dB. Q2. [AS1] What are the differences between the noise and music? Explain. [Refer to TB page 81 Q3] A. S.No. Music Noise 1 The sounds which are The sounds which are pleasant to hear are not pleasant to hear are called music. called noise. 2 Music is a combination Noise is an irregular of sounds that are combination of sounds produced in an order which are ‘unpleasant’ to and pleasant to hear. hear. Q3. [AS1] Explain the sources which produce sound pollution in your surroundings. [Refer to TB page 81 Q4] A. In our surroundings there are many sources causing sound pollution, like sounds of traffic, vehicle horns, sounds in construction sites, sounds at industries, sounds at mines, sounds during explosions and bursting of crackers, etc. Q4. [AS7] Write your suggestions to reduce sound pollution. [Refer to TB page 81 Q5] A. i. Minimising sounds produced by horns of vehicles. ii. Minimising the sounds produced by music systems. iii. Barring the usage of PA systems during festival celebrations and meetings. iv. Growing plants which are natural absorbers of sound. v. Attaching silencers to bikes and other machines to reduce sounds. SESSION 3. CHARACTERISTICS OF SOUND AND SOUND POLLUTION 135

vi. Manufacturing machines that work with less noise. vii. Toning down the volume of sound during the use of TVs and music players. 3.5 Application of Concepts Q1. [AS1] The sound of crickets (insects) makes us close our ears. Why? [Refer to TB page 81 Q1] A. Crickets make sounds that are of high pitch. The higher the pitch the greater the fre- quency. High frequency means the ear drum vibrates very fast which causes irritation. Q2. [AS7] Write any two slogans to reduce sound pollution. [Refer to TB page 81 Q3] A. i.Let the world be in peace. Reduce noise pollution. ii.Keep noise down otherwise noise will keep you down. iii.More you make your noise faster you lose your voice. iv.Silence is the best way to decrease noise pollution. 3.6 Higher Order Thinking Skills Q1. [AS7] How does sound pollution affect biodiversity? Explain. [Refer to TB page 82 Q2] A. Noise pollution causes a lot of damage to the human ear. It alters birds’ behaviour. Due to industrial noise some birds are migrating from one place to another. People experiencing high noise levels suffer from sleep deprivation and headache. 3.7 Suggested Experiments Q1. [AS3] Conduct an experiment to know the relationship between the intensity of sound produced by a body and the vibrations of the body. [Refer to TB page 82 Q1] A. Aim: To know the relation between the intensity of sound produced by a body and the vibrations of the body. SESSION 3. CHARACTERISTICS OF SOUND AND SOUND POLLUTION 136

Materials required: Wooden table, 30 cm metal scale or 30 cm hack– saw blade and a brick. Procedure: i. Place the blade/scale on a table, with 10 cm of the blade on the surface of the table and rest of it in the air. Keep a heavy brick on 10 cm of the blade/scale kept on table. ii. Vibrate the blade gently and observe the vibrations and simultaneously listen to the sounds. Repeat the same 2–3 times and record observations in the table shown below. iii. Vibrate the blade using higher force. Observe the vibrations and listen to the sound. Repeat this 2–3 times and record observations in the table shown below. FORCE VIBRATIONS OF INTENSITY OF Small THE BLADE/SCALE SOUND Large 30 less 50 more We will observe that when we apply a large force we hear a loud sound. When we apply less force we hear less sound. During loud sound the frequency of vibration is more, during feeble sound the frequency of vibration is less. SESSION 3. CHARACTERISTICS OF SOUND AND SOUND POLLUTION 137

Q2. [AS3] Conduct an experiment to identifying Pitch or Shrillness of a sound. [Refer to TB page 82 Q2] A. Aim: Identifying pitch or shrillness of a sound. Material required: A wooden table, two hack–saw blades or metal scales of 30 cm length and a brick. Procedure: i. Place the first blade/scale on the table, with 10cm portion of the blade on the table and rest of it in air. Keep a brick as weight on the 10 cm portion of the blade/scale kept on the table. ii. Place the second blade/scale on the table (see that the gap between these two blades is 10cms), with 25cm on the table and 5cm in air. Keep a brick as weight on the scale/blade . iii. Vibrate both blades with same force. Observe the vibrations and listen to the sounds produced. OBSERVATION: BLADE LENGTH Vibrations Sound IN AIR 50 Less shrillness More shrillness Blade 1 : 20 cm 90 Blade 2 : 5 cm SESSION 3. CHARACTERISTICS OF SOUND AND SOUND POLLUTION 138

We will observe that number of vibrations produced are less in 20cm long blade/ scale when compared to vibrations of 5cm long blade/scale. The sound produced by 5 cm long blade/scale is more shrill than that of 20 cm long bade/scale. 3.8 Suggested Projects Q1. [AS4] Collect photographs showing various situations of sound pollution and prepare a report. [Refer to TB page 82 Q1] A. Students’ activity. Objective Questions (1) The audible sound range of man is –(Pg 82;TB Q 3) (A) 10 –10000 Vibrations/sec (B) 20 –20000 Vibrations/sec (C)30 –30000 Vibrations/sec (D)40 –40000 Vibrations/sec Correct Answer: B (2) The shrillness of a sound is known as –(Pg 82; TB Q5) (A) Pitch (B) Vibration (C) Intensity (D) Decibel Correct Answer: A SESSION 3. CHARACTERISTICS OF SOUND AND SOUND POLLUTION 139

—— CCE Based Practice Questions —— AS1-Conceptual Understanding [] Very Short Answer Type Questions [] 1. State true or false. [Refer to Session 5.1 ] (i) String is the vibrating part that produces sound in tabla. (ii) It is possible to produce sound without vibration. (iii) All types of sound have energy. [] (iv) Bismillah Khan is an outstanding shehnai player. [] 2. Fill in the blanks. [Refer to Session 5.2 ] (i) Sound cannot travel through . (ii) The sound vibrations are transformed into and carried by the to the brain. (iii) Sound travels fastest through medium. (iv) bone is of a hammer shaped. 3. Fill in the blanks. [Refer to Session 5.3 ] (i) Frequency of audible sound ranges from . (ii) is the unit for measuring intensity of sound. (iii) Unwanted sounds in our surroundings leads to . CHAPTER 5. SOUND 140

(iv) The shrillness of a sound is known as . (v) is the number of vibrations per second. (vi) The of a sound depends upon frequency. Short Answer Type Questions 4. Answer the following questions in 3-4 sentences. (i) [(Session 5.1)] Name any two musical instruments you know and explain how they produce sound. 5. Answer the following questions in 3-4 sentences. (i) [(Session 5.2)] What are the functions of cochlea? CHAPTER 5. SOUND 141

Long Answer Type Questions 6. Answer the following questions in 6-8 sentences. (i) [(Session 5.3)] What is the difference between noise and music? Do you think that music can become noise sometimes? CHAPTER 5. SOUND 142

AS2-Asking questions and making hypothesis Short Answer Type Questions 7. Answer the following questions in 3-4 sentences. (i) [(Session 5.3)] How is a word, sound of mixed frequencies? (ii) [(Session 5.3)] You live in a house which is at the centre of the city. Traffic is more there. So, your father wants to change the house. Why do you think he wants to change the house? CHAPTER 5. SOUND 143

Long Answer Type Questions 8. Answer the following questions in 6-8 sentences. (i) [(Session 5.3)] Sonam stays in an apartment. At the time of Diwali, a message was circulated in her apartment with the following instructions: 1) Do not burst crackers in the corridors. 2) Burst them on terrace from 7 –9 pm only. Sonam likes to burst crackers but has many doubts after reading the notice. What questions she might have asked to clarify the doubts? AS3-Experimentation and field investigation Long Answer Type Questions 9. Answer the following questions in 6-8 sentences. (i) [(Session 5.1)] How do you show that sound has energy with an activity? CHAPTER 5. SOUND 144

AS4-Information skills and projects Very Short Answer Type Questions 10. Answer the following questions in one sentence. [Refer to Session 5.1 ] (i) Complete the table. S.No. Instruments Part of the instruments vibrate 1 Tabala Stretched membrane 2 Veena Stretched string 3 Flute 4 Violin CHAPTER 5. SOUND 145

11. Answer the following questions in one sentence. [Refer to Session 5.3 ] (i) Answer the questions by analyzing the table. S.No. Characteristics Effect on sound 1 Frequency As frequency increases sound becomes shriller 2 Amplitude As amplitude increases sound become louder i. Pitch of the sound depends on the characteristic . ii. Loudness of the sound depends on the characteristic . CHAPTER 5. SOUND 146

Long Answer Type Questions 12. Answer the following questions in 6-8 sentences. (i) [(Session 5.3)] Collect information on the health hazards of machine sounds by taking an interview of a person working with machines in an industry. CHAPTER 5. SOUND 147

AS5-Communication through drawing and model making Short Answer Type Questions 13. Answer the following question. (i) [(Session 5.2)] Draw the structure of ear. Long Answer Type Questions 14. Answer the following questions. (i) [(Session 5.1)] Observe the instruments and identify the part which vibrates to pro- duce sound in the following instruments. CHAPTER 5. SOUND 148