Balbharti Maharashtra State Board Class 9 Science Solutions Chapter 14 Substances in Common Use Notes, Textbook Exercise Important Questions and Answers.

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Maharashtra State Board Class 9 Science Solutions Chapter 14 Substances in Common Use

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Q. 1. Fill in the blank and rewrite the completed statements 12

1. The chemical name of Teflon is …………… .

Ans The chemical name of Teflon is Polytetra fluroethene.

2. …………… is used for coating cooking utensils to avoid sticking.

Ans Teflon is used for coating cooking utensils to avoid sticking.

3. Bleaching powder is obtained by the reaction of chlorine gas with …………… .

Ans Bleaching powder is obtained by the reaction of chlorine gas with Slaked lime.

4. Blue vitrol is used in the blood test for diagnosing …………… .

Ans Blue vitrol is used in the blood test for diagnosing Anaemia.

5. ………….is used in the treatment of hyperthyroidism.

Ans Iodine – 123 Is used in the treatment of hyperthyroidism.

6. The number of molecules of water of crystallization in washing soda is …………… .

Ans The number of molecules of water of crystallization in washing soda is 10.

7. The 25% aqueous solution of salt is called …………… .

Ans The 25% aqueous solution of salt is called Saturated brine.

8. The chemical name of baking soda is …………… .

Ans The chemical name of baking soda is Sodium bicarbonate.

9. Excessive consumptions of foods with added food colors can lead to diseases like …………… .

Ans Excessive consumptions of foods with added food colors can lead to diseases like ADHD (Attention Deficit Hyperactivity Disorder)

10. The chemical name of bleaching powder is …………… .

Ans The chemical name of bleaching powder is Calcium oxychloride.

11.Food colors added in pickles , jam and sauce contains …………… and in small quantities.

Ans: Food colors added in pickles , jam and sauce contains Lead and Mercury in small quantities.

12. Full Form of ADHD is …………… .

Ans Full Form of ADHD is Attention Deficit Hyperactivity Disorder

Q .2. Find the odd one out 4

1. Boron-10, Iodine -131, Cobalt-60, Radium-223

Ans Radium-223 – is used in the treatment of bone cancer in the body while rest is used in the treatment of brain tumour.

1. Sodium chloride, Sodium bicarbonate, Sodium carbonate, Hydrogen chloride.

Ans Hydrogen chloride – is an acid while rest are salts.

1. Soap, Baking soda, Milk, Washing soda.

Ans Milk – is acidic in nature while rest is basic in nature.

1. Magnesium sulphate, Sodium sulphate, Barium chloride, Sodium chloride.

Ans Sodium chloride – it doesn’t contain water of crystallization while the rest contains the molecules of water of crystallization.

Q. 3. Find co-related terms 7

1. Sodium carbonate : refining of petrol : : Bleaching of cloth.

Ans : Sodium carbonate : refining of petrol : : Calcium oxy chloride : Bleaching of cloth.

1. Milk : Acidic :: Soap: …………… .

Ans : Milk : Acidic :: Soap: Basic

1. Phosphorus – 32 : polycythemia :: Radium 223 : …………… .

Ans : Phosphorus – 32 : polycythemia :: Radium 223 : Bone cancer.

1. Washing Soda : :: Bleaching Powder : Calcium oxychloride.

Ans: Washing Soda : Sodium carbonate :: Bleaching Powder : Calcium oxychloride.

1. Magnesium sulphate : MgSO₄.7H₂O :: Barium chloride : …………… .

Ans Magnesium sulphate : MgSO₄.7H₂O :: Barium chloride : BaCl₂.2H₂O_.

1. Sodium bicarbonate : NaHCO₃ :: Calcium oxychloride : …………… .

Ans Sodium bicarbonate : NaHCO₃ :: Calcium oxychloride : CaOCl₂

1. Natural food color : Beetroot :: Artificial food color : …………… .

Ans Natural food color : Beetroot :: Artificial food color : Tetrazene, Sunset yellow.

Q.4. Match the pair 4

1.

Column ‘A’	Column ‘B’
i. CaOCl2	a. Basic salt
ii. NaHCO3	b. Sodium metal freed
	c. Oxidation of colour

Ans

i. CaOCl2	Oxidation of colour
ii. NaHCO3	Basic salt

2.

Column ‘A’	Column ‘B’
i. Saturated brine	a. Sodium metal freed
ii. Fused salt	b. Crystallization of salt
	c. Oxidation of colour

Ans

i. Saturated brine	Crystallization of salt
ii. Fused salt	Sodium metal freed

3.

Column ‘A’	Column ‘B’
i. Cobalt-60	a. Bone Cancer
ii. Lodine-123	b. Brain Tumor
	c. Hyperthyroidism

Ans

i. Cobalt-60

Brain Tumor

Hyperthyroidism

ii. Lodine-123

4.

Column ‘A’	Column ‘B’
i. Sodium carbonate	a. Refining of petrol
ii. 25% sodium chloride solution	b. Saturated brine.
	c. Fire extinguisher

Ans

i. 25% sodium chloride solution	Saturated brine.
ii. Sodium carbonate	Refining of petrol

Q. 5. State True or False 13

1. Clinical deo contains 20- 25 % of aluminium.

Ans Clinical deo contains 20- 25 % of aluminium – True

2. Teflon coated articles are easy to clean.

Ans Teflon coated articles are easy to clean – True

3. The hard water becomes soft on adding sodium bicarbonate.

Ans False – The hard water becomes soft on adding sodium carbonate.

4. Sodium bicarbonate is used in the preparation of CO₂ in the fire Extinguisher.

Ans Sodium bicarbonate is used in the preparation of CO₂ in the fire Extinguisher – True

5. The radioactive paint on watch can cause cancer.

Ans The radioactive paint on watch can cause cancer – True

6. Ceramics can withstand high temperatures without decomposing.

Ans Ceramics can withstand high temperatures without decomposing – True

7. Bleaching powder is used in preparation of chloroform.

Ans Bleaching powder is used in preparation of chloroform – True

8. Anodizing is done by electrolysis.

Ans Anodizing is done by electrolysis – True

9. Washing powder is also called as chloride of lime.

Ans False – Bleaching powder is called as chloride of lime.

10. Sodium bicarbonate is used to reduce acidity.

Ans Sodium bicarbonate is used to reduce acidity – True

11. Boron -10 is used in the treatment of bone cancer.

Ans False – Boron-10 is used in the treatment of brain tumor.

12. Chlorine gas is a strong reducing agent.

Ans False – Chlorine gas is a strong oxidizing agent.

13. Soap is acidic in nature.

Ans False – Soap is basic in nature.

Q. 6. Name the following 20

1. The constituents of Baking powder.

Ans Sodium bicarbonate and tartaric acid.

2. Why is colored metal sheets of two-wheelers given a Teflon coating?

Ans To protect from damage due to high temperature and rain.

3. Which substance is used for making non – stick kitchenware?

Ans Teflon

4. One use of baking powder.

Ans In the preparation of Cake, To reduce acidity in the stomach.

5. Examples of common ceramic articles.

Ans Pots made by a potter, Mangalore roofing tiles, construction bricks, pottery, terra-cotta articles are some examples of common ceramic articles.

6. The chemical name of Teflon.

Ans Polytetrafluoroethylene

7. A radioactive substance.

Ans Uranium, Thorium, Radium.

8. When is clinical deo applied by the person?

Ans It is applied in the night.

9. Name the process that you see in the following picture.

Ans The above picture refers to the process of powder coating.

10 .Full form of ADHD.

Ans Attention Deficit Hyperactivity Disorder.

11. Substance that contains water of crystallization.

Ans Sodium Sulphate (Na₂SO₄.10 H₂O)

12. Salt that can be used to clean the oven.

Ans Baking soda (Sodium Bicarbonate)

13. Name the disease caused due to over consumption of artificial food colors.

Ans Attention Deficit Hyperactivity Disorder (ADHD).

14. Is Teracotta an example of Ceramic or Porcelain?

Ans Ceramic

15. What is caused by the bacterial decomposition of sweat?

Ans Body odour

16. The chemical formula of bleaching powder.

Ans CaOCl₂

17. Use of Cobalt-60 in the field of agriculture.

Ans Used for food preservation.

18. Substance used to make hard water soft.

Ans Washing soda (Sodium carbonate)

19. Two examples of rock salt.

Ans Mineral halite, Himalayan rock salt.

20. Any one artificial food color.

Ans Tetrazene, Sunset Yellow

Q. 7. Multiple Choice Questions 11

1. Strong odour in the swimming pool is due to ……………

a.Impurities                     b. Calcium carbonate

c. Chlorine gas                  d. Sodium chloride

Ans Option c.

2. Sodium carbonate is used for …………….

a. Reduce acidity               b. Washing clothes

c. Disinfecting garbage sites d. Paper industry

Ans Option b.

3. The molten state of NaCl is called ……………

a. Gaseous state                   b. Liquid state

c. Fused state                      c. Aqueous state

Ans Option c.

4. is used to make hard water soft.

a. Sodium carbonate b. Sodium chloride

c. Calcium carbonate d. Calcium chloride.

Ans Option a.

5. Salt obtained from certain type of rock is called …………… .

a. Rock salt b. Pure salt c. Hard salt d. Table salt

Ans Option a.

6. is also called as chloride of lime.

a. Bleaching powder b. Washing soda

c. Baking soda d. Sodium chloride

Ans Option a.

7. Molecular formula of sodium hydrogen carbonate is …………… .

a. NaHCO₃

Ans Option a.

b.Na₂CO₃

c. Ca(CO)₃

d. Ca(OH)₂

8. is used for making non-stick kitchen ware.

a. Rayon b. Nylon c. Teflon d. Acrylic

Ans Option c.

9. The % aqueous solution of salt is called brine.

a. 20 b. 25 c. 30 d. 50

Ans Option b.

10 .The chemical name of Bleaching powder is …………….

a. Calcium oxygen chloride b. Calcium oxychloride

c. Calcium chloride d. Calcium carbonate

Ans Option b.

11. gas is released when bleaching powder is exposed to air.

a. Chlorine b. Hydrogen c. Oxygen d. Carbon dioxide

Ans Option a.

Q. 8. Write Short Notes 18

1. Bleaching Powder

Ans i. Bleaching powder is a yellowish white coloured solid substance.

ii. Its chemical name is Calcium oxy chloride.

iii. It has a strong odour of chlorine gas.

iv. Dilute sulphuric acid and dilute hydrochloric acid react rapidly with bleaching powder to release chlorine gas completely.

v. Calcium oxy chloride reacts slowly with carbon dioxide to form calcium carbonate and chlorine.

2. Radioactive isotopes in Medical science.

Ans i. Polycythemia: The red blood cell count increases in the disease polycythemia. Phosphorus-32 is used in its treatment.

ii. Bone Cancer: Strontium-89, Strontium- 90, Samarium-153 and radium- 223 are used in the treatment of bone cancer.

iii. Hyperthyroidism: Enlargement of thyroid gland, weight loss in spite of appetite, insomnia are the symptoms of hyperthyroidism. It occurs due to overproduction of hormones by the thyroid gland. Iodine – 123 is used in the treatment of hyperthyroidism.

iv. Tumour detection: Boron- 10, Iodine -131, Cobalt- 60 are used in treatment of. Brain tumour while Arsenic-74 is used in detection of small tumours in the body.

3. Teflon:

Ans i. Teflon is a poor conductor of electricity. Therefore, Teflon cladded wires and parts are used in high technology electronics instruments.

ii. Teflon is used for making non-stick kitchenware.

iii. The colored metal sheets of two wheelers and four- wheelers are given a Teflon coating to protect them from damage due to high temperature and rain.

iv. The atmosphere and chemical substances have no effect on Teflon.

v. Neither water nor oil will stick to Teflon coated articles.

vi. High temperatures do not affect Teflon as its melting point is 327⁰C.

vii. Teflon coated articles are easy to clean.

4. Radioactive isotopes.

Ans: i. Radioactive isotopes are used in various fields such as scientific research, agriculture industry, medicine, etc

ii. Radioactive substances are used in two ways

1.By using the radiation alone.     2. By using the radioactive element itself.

5. Radioactive isotopes in field of agriculture.

Ans i. The genes and chromosomes that give seeds properties like fast growth, higher productivity, etc. can be modified by means of radiation.

ii. The radioactive isotope cobalt-60 is used for food preservation.

iii. Onions, potatoes are irradiated with gamma rays from cobalt-60 to prevent their sprouting.

iv. Strontium-90 is used as a tracer in the research on various crops.

6. Radioactive isotopes in Radiography.

Ans i. Internal cracks and voids in cast iron articles and iron solder can be detected with the help of gamma rays.

ii. For this purpose, isotopes like cobalt-60, iridium-192 are used in the radiography camera.

iii. This technique is used for detecting flaws in metal work.

7. Deodorants.

Ans i. Body odour is caused by the bacterial decomposition of the sweat. A deodorant is used to prevent this odour.

ii. Deodorants contain parabens (methyl, ethyl, propyl, benzyl and butyl) and also alcohol in large proportions.

iii. Aluminium compounds and silica are also used.

iv. Ordinary deo: It contains a smaller proportions of aluminium. It decreases the odour of the sweat.

v. Antiperspirant deo: This decreases the extent of sweating. It contains about 15% of aluminium chlorohydrate. It clogs the sweat pores on the skin.

vi. Clinical deo: Clinical deo is meant for people sweat heavily and it has harmful effects on the skin. It contains 20 to 25% aluminium. It is used during night.

8. Food Colors.

Ans i. Food colors are substances that are added to make the food more attractive.

ii. They are mixed in most soft drinks and foodstuffs available in the market. These food colors are in the form of powders, gels and pastes.

iii. Food colors are naturals as well as artificial.

iv. Food colors prepared from seeds, beetroot, flowers and fruit concentrate are called natural food colors.

v. Tetrazene, sunset yellow are examples of artificial food colors.

vi. They are used in domestic as well as commercial products.

vii. These are found added to packaged meat, chilli powder, turmeric, sweets and other similar substances so as to give them a good color.

viii. Food colors are added to pickles, jam and sauce contain small quantities of lead and mercury.

ix. Over- consumption of artificial food colors can be harmful to health.

9. Sodium chloride.

Ans i. Common salt is a colourless and crystalline ionic compound.

ii. There is no water of crystallization in its crystalline structure.

iii. IT is a neutral salt, salty in taste.

iv. When salt is heated to a high temperature(about 800⁰ C), it melts. This is called the fused state of the salt.

When fused salt is electrolyzed, chlorine gas is released at the anode and liquid sodium metal, at the cathode.

Q.9. Chemical reaction with equation: 16

1. Crystalline sodium carbonate is exposed to air:

When crystalline sodium carbonate is exposed to air it loses its water of crystallization readily and a white powder is obtained. This powder is called washing soda.

Ans Na₂CO₃.10H₂O → Na₂CO₃.H₂O

Crystalline White powder Sodium carbonate (Washing soda)

2. Bleaching powder reacts with dilute sulphuric acid.

Dilute sulphuric acid reacts rapidly with bleaching powder to form calcium sulphate with the release of chlorine gas.

Ans CaOCl₂

• H₂SO₄ →

CaSO₄

• Cl₂

• H₂O

Bleaching Sulphuric Calcium Chlorine Water Powder Acid Sulphate Gas

3 . Sodium carbonate reacts with magnesium chloride.

When sodium carbonate reacts with magnesium chloride, it forms insoluble magnesium carbonate and sodium chloride.

Ans MgCl₂

• Na ₂CO₃ →

MgCO₃

• 2NaCl

Magnesium Sodium Magnesium Sodium Chloride Carbonate Carbonate Chloride

4. Sodium carbonate reacts with sulphuric acid:

When sodium carbonate reacts with sulphuric acid it forms sodium sulphate, water and carbon dioxide gas is liberated.

Ans Na₂CO₃

• H₂SO₄ →

Na₂SO₄

• H₂O + CO₂

Sodium Sulphuric Sodium Water Carbon Carbonate Acid Sulphate Gas Dioxide

5. Bleaching powder is exposed to air.

When bleaching powder is exposed to air, it undergoes slow decomposition due to the carbon dioxide in the air with the release of chlorine gas.

Ans CaOCl₂

• CO₂ →

CaCO₃

• Cl₂

Bleaching Carbon Calcium Chlorine Powder Dioxide Carbonate Gas

6. Give the reactions for following

An electrical current is passed through a saturated solution of sodium chloride(brine),

Ans When an electrical current is passed through a saturated solution of sodium chloride(brine), it is electrolyzed and hydrogen gas is released at the cathode while chlorine gas is released at the anode along with formation of sodium hydroxide in the cell.

2NaCl + 2H₂O

→ 2NaO + Cl₂

• ↑ H₂ ↑

Sodium Water Sodium Chlorine Hydrogen Chloride Hydroxide Gas Gas

7. Sodium bicarbonate (Baking soda) reacts with dilute hydrochloric acid. When sodium bicarbonate reacts with dilute hydrochloric acid, it forms sodium chloride and water along with liberation of carbon dioxide gas.

Ans NaHCO₃

• HCl

→ NaCl + H₂O + CO_2l

Sodium Hydrogen Sodium Water Carbon Bicarbonate Chloride Chloride Dioxide

8. When dry slaked lime reacts with chlorine gas.

Bleaching powder is obtained by the reaction of dry slaked lime ( Calcium hydroxide) reacts with chlorine gas.

Ans Ca(OH)₂

• Cl₂ →

CaOCl₂

• H₂O

Calcium Chlorine Bleaching Water Hydroxide Gas Powder

Q.10. Attempt the following. 42

1. Define detergents.

Ans i. Detergents are water soluble cleansing agents. They are generally liquids rather than solids.

1. Detergents contain chemical called surfactants.
2. Detergents are used in washing powder, shaving foam, stain remover etc.

2. State 4 uses of baking powder.

Ans 1. It is used to make bread, cake, dhokla.

• 1. Being basic in nature it is used to reduce acidity in the stomach.
  2. NaHCO3 is used to make the active substance CO2 in the fire extinguisher.
  3. Baking soda is used to clean an oven.

3. What is the strip shown below? What is it used for?

Ans i. The strip shown below is pH metre scale .

ii. It is used to determine the pH of the given solution.

4. Write uses of deodorants.

Ans i. Body odour is caused by the bacterial decomposition of sweat. A deodorant is used to prevent this odour.

ii.Deodorants contain parabens (methyl, ethyl, propyl, benzyl and butyl) and also alcohol in large proportions. Aluminium compounds and silica are also used.

5. Write the harmful effects of Artificial dye.

Ans i. Dyeing hair can have adverse effects like hair fall, damage to hair texture, burning of skin, adverse effect on eyes, etc.

1. Lipstick contains a dye named carmine. It does not affect lips but causes stomach disorders.
2. Excessive use of plants for making natural dyes results in deterioration of the environment.

6. A doctor gives you medicines when you fall ill. What are the medicines made from?

Ans i. The medicines today are made from chemical compounds which are standardized and tested in the laboratory by the chemists.

ii. In olden days before pure chemicals were manufactured in labs, people used plants for medicine.

7. Define ceramic along with examples.

Ans i. Ceramic is a heat resistant substance formed by kneading an inorganic substance in water and then shaping it and hardening it by heating.

ii. Pots made by potter, Mangalore roofing tiles, construction bricks, pottery, terracotta articles are some examples of common ceramic articles that we see around.

8. Write down the properties of Teflon.

Ans i. The atmosphere and chemical substances have no effect on Teflon.

1. Neither water nor oil will stick to Teflon coated articles.
2. High temperatures do not affect Teflon as its melting point is 327⁰C.
3. Teflon coated articles are easy to clean.

9. Define salts with example.

Ans i. The ionic compounds which do not contain H+ and OH- ions and contain only one kind of cation and anion are called simple salts.

ii. For example: Na₂SO₄, CaCL₂

10. Write uses of Anodizing.

Ans 1. Anodizing is most common for improving corrosion resistance on certain alloys.

• 1. It’s been used for dyeing metals.
  2. It can also be used for electrical insulation.

11. Write uses of Radioactive substances.

Ans 1. Radioactive elements are used for making atom bomb.

1.Radioactive isotopes are used in various fields such as scientific research, agriculture, industry, medicine, etc.

1. The radioactive substances radium, promethium, tritium with some phosphor are used to make certain objects visible in the dark.

12. Give the uses of Dyes.

Ans i. Dye is used for coloring cloth and hair.

1. Fluorescent colors are used to make street boards that are visible at night.

1. Dyes are used to polishing leather shoes, purses, and chappals.

13. Write uses of Ceramic

Ans i. Mangalore roofing tiles, terracotta articles, construction bricks, pottery, etc. are various ceramic articles that are commonly used.

1. Ceramics are used in electrical instruments, for coating the interior of a kiln, the outer surfaces of ships and blades of jet engines.
2. A certain type of ceramic tiles are fixed on the outer layer of a space shuttle.
3.  Certain types of ceramics are also used as superconductors.

14. Write the harmful effects of artificial food colors.

Ans i. Food colors are added to pickles, jam and sauce contain small quantities of lead and mercury.

1. Over- consumption of artificial food colors can be harmful to health.
2. Diseases like ADHD( Attention Deficit Hyperactive Disorder) can affect children due to excessive consumption of foods with added food colors.

15. Write the chemical formula of bleaching powder, common salt, baking soda and washing soda.

Ans i. Beachling powder – CaOCl₂

1. Common salt – NaCl
2. Baking soda – NaHCO₃
3. Washing soda – Na₂CO_3..10H₂O

16. Write uses of Powder coating

Ans i. Powder coating is done on Iron objects to prevent rusting.

ii. Powder coating is done on plastic and medium density fibre (MDF) board to make them highly durable, hard and attractive.

17. Write the harmful effects of radioactive substance.

Ans i. The central nervous system is affected by radioactive radiations.

1. Hereditary disorders are caused by bombardment of radiation on DNA in the body.
2. Radiations can penetrate the skin and cause diseases like skin cancer, leukemia.
3. The radioactive pollutants released in sea enter the bodies of fishes and through them enter the human body.
4. The radioactive paint on the watch can cause cancer.
5. The radioactive isotopes strontium-90 can enter the body through plants, fruits, flowers, cereals, milk, etc., and cause diseases like bone cancer, leukemia.

18. Take a piece of colored cloth. Put some saturated solution of bleaching powder on a small part and observe what changes take place on the cloth?

Ans When bleaching powder is added to a piece of coloured cloth, the fabric loses its color due to the oxidizing reaction of the chlorine present in the bleaching powder.

19. Write the harmful effects of deodorants.

Ans i. Aluminium – Zirconium compounds are the most harmful chemicals in the deodorant. Disorders like headache, asthma, respiratory disorders, heart disease are likely to occur without our knowledge.

ii. There is a possibility of various skin disorders and skin cancer due to aluminium chlorohydrates.

20. Define radioactivity.

Ans i. Elements with a high atomic number such as uranium, thorium, radium have a property of spontaneously emitting invisible, highly penetrating and high energy radiations.

1. This property is called radioactivity.
2. A substance having this property is called radioactive substance.

21. Soap is very basic item that is used in our day to day life.

Can you name the chemicals and apparatus used in the laboratory for making soap?

Ans i. Chemicals used in soap: vegetable oil( coconut oil, castor oil, etc.), Sodium hydroxide, salt.

ii. Apparatus: glass beaker, burner, glass tray, knife.

Q.11. Distinguish between 6

1. Give the differences between Alpha rays and Gamma rays.

Ans

	Alpha rays (α)	Gamma rays (γ)
i.	It is a current of alpha particles.	It is an electromagnetic radiation.
ii.	It has a charge of +2 and a mass of 4.0028 u.	It is electrically neutral and has no mass.
iii.	It has very high ionization power.	It has very low ionization power.
iv.	It produces very high fluorescence.	It produces low florescence.

2. Bathing soap and Washing soap.

Ans

	Bathing soap	Washing soap
i.	Bathing soap contains high grade fats and oils as raw material	Washing soap contains low grade fats and oils as raw material.
ii.	Expensive perfumes are added	Cheaper perfumes are added
	No free alkali content present to prevent injuries to skin
iii.		Free alkali is present in soap for cleaning action

3. Washing soda and Baking soda.

Ans

	Washing soda	Baking soda
i.	The chemical name of washing soda is Sodium carbonate	The chemical name of baking soda is Sodium bicarbonate
ii.	The molecular formula is Na2CO3	The molecular formula is NaHCO3
iii.	It is crystalline in nature	It is amorphous in nature
	When heated loses the water of crystallization.	When heated it decomposes to form sodium carbonate, CO2 and water
iv.

Q.12. Give scientific reasons: 18

1. A certain type of ceramic tiles are fixed on the outer layer of a space shuttle.

Ans i. Ceramic is brittle, water resistant and an electric insulator.

ii. Ceramics can withstand high temperatures without decomposition.

iii. Space shuttle is covered by advanced ceramic tiles.

iv. Most of the tiles are made of silica fibers, which are produced from high grade sand.

v. Silica is an excellent insulator as it transports heat slowly.

vi. When the outer portion of a tile gets hot, the heat takes along time to work its way down through the rest of the tile to the shuttle’s skin.

2. Alum is used in the process of water purification.

Ans i. Alum is used in the process of water purification because of the property of coagulation.

ii. The solid impurities in water come together, become heavy and settle to the bottom.

iii. As a result, the water above becomes clear.

3. Artificial colors in Rang Panchami should be avoided.

Ans i. . Artificial colors are prepared from chemicals/dyes which are very dangerous.

ii. The red color in the dye contains high proportion of mercury in it.

iii. This poses risks like blindness, skin cancer, asthma, itching of the skin, permanent blocking of sweat pores etc.

iv. Therefore artificial colors in Rang Panchami should be avoided and natural colors obtained from vegetables, flowers should be used.

4. Baking soda is used while making cakes.

Ans i. Baking soda is chemically known as Sodium bi carbonate.

ii. On heating, sodium bicarbonate decomposes to form sodium carbonate, water and carbon dioxide.

iii. This carbon dioxide released makes the cake soft and spongy.

iv. Hence, baking soda is added to make the cake soft and spongy.

5. Over consumptions of artificial food colors should be avoided.

Ans i. . Food colors added to pickles, jam and sauce contain small quantities of lead and mercury.

ii. These can be harmful for those who consume these products on a regular basis.

Iii .Diseases like ADHD( Attention Deficit Hyperactivity Disorder) can affect children due to excessive consumption of foods with added food colors.

iv. Hence, over consumption of artificial food colors should be avoided as they can be detrimental to health.

6. The aluminium article is used as an anode in the anodizing process.

Ans i. A protective layer is formed naturally on the surface of aluminium metal by reaction with oxygen in the air.

In the anodizing process, this layer is made of the desired thickness by electrolysis.

ii. Dilute sulphuric acid is taken in the electrolytic cell and the aluminium article is dipped in it as anode.

iii. When an electric current is passed, hydrogen gas is released at cathode and oxygen gas at the anode.

iv. A reaction with oxygen occurs and a layer of hydrated aluminum oxide is formed on the anode.

v. Therefore aluminium article is used as an anode in the anodizing process.

7. Soap forms a precipitate in hard water.

Ans i. When oil or animal fat is boiled with an aqueous solution of sodium or potassium hydroxide, sodium or potassium salts of carboxylic acids are formed. These salts are called soap.

ii. When soap is mixed with hard water, calcium and magnesium salts of fatty acids are formed.

iii. These salts being insoluble in water, form a precipitate and hence lather formation does not take place.

8. Bleaching powder has the odour of chlorine gas.

Ans i. Bleaching powder is chemically called as Calcium oxychloride.

ii. Bleaching powder undergoes slow decomposition due to the carbon dioxide in air and continuously chlorine gas is released.

CaOCl₂     +    CO₂ → CaCO₃    + Cl₂

iii. Bleaching Carbon Calcium Chlorine Powder Dioxide Carbonate Gas

iv. Bleaching powder gets its property because of this release of chlorine gas.

9. The hard water of a well becomes soft on adding washing soda to it.

Ans i. The hardness of water is due to the presence of chlorides and sulphates of calcium and magnesium in it.

ii. Sodium carbonate (washing soda) is added to this hard water to make it soft with formation of lather and also suitable for use.

iii. When washing soda is added to hard water, it leads to the formation of insoluble carbonate salts of calcium and magnesium.

iv. MgCl₂      + Na₂CO₃ → MgCO₃    + 2NaCl

Q.13. Write Laws, theories and explain 3

1. Explain Anodizing.

Ans i. A protective layer is formed naturally on the surface of aluminium metal by the reaction of oxygen in the air.

ii. In the anodizing process, this layer can be made of the desired thickness by electrolysis.

iii. Dilute sulphuric acid is taken in the electrolytic cell and the aluminium article is dipped in it as the anode.

iv. When an electric current is passed, hydrogen gas is released at the cathode and oxygen gas at the anode.

v. A reaction with oxygen occurs and a layer of hydrated aluminium oxide is formed on the anode i.e. the aluminium article

vi. This layer can be made attractive by adding color in the cell during electrolysis.

Q.14. Give examples 8

1. Give 4 examples of Diseases caused by artificial food colours.

Ans 1. ADHD (Attention Deficit Hyperactivity Disorder)

1. Cancer        2.Allergies        3. Asthma

2. Give 4 examples of items in which colors and essences are added.

Ans ice cream, ice candies, sauce, fruit juices, cold drinks, pickles, jams, and jelly.

3. Give examples of salts with water of crystallization. (any 4)

Ans i. Alum ( Potash alum) – K₂SO₄.Al₂(SO₄)_3. 24H₂O

ii. Borax (Na₂B₄O₇. 10 H₂O )

iii. . Epsom salt ( Magnesium sulphate MgSO₄.7H₂O)

iv. Barium chloride ( BaCl₂.2H₂O)

v. Sodium sulphate ( Glauber’s salt Na₂SO₄. 10 H₂O)

vi. Blue Vitriol (Copper sulphate-CuSO_4. 5H₂O)

4. Give 4 example of important salts found in sea water

Ans 1.Sodium chloride 2.Magnesium chloride 3.Magnesium sulphate 4.Potassium chloride 5.Calcium carbonate 6.Magnesium bromide

Q.15. Give explanation using the given statement: 6

1. When radiation coming out from certain radioactive substance is passed through an electric field, marks are found at three places on the photographic plate placed in its path. Explain

Ans: I . When radiation coming out from certain radioactive substance is passed through an electric field, marks are found at three places on the photographic plate placed in its path. This is because the radiation coming out of the radioactive substance is of three types Alpha rays, Beta rays and Gamma rays.

ii. The rays which get deviated slightly towards negatively charged plate are called alpha rays as they are made of positively charged.

iii. The rays which get deviated substantially toward the positively charged plate are called beta rays as they are negatively charged.

iv. The rays which do not deviate at all are called gamma rays. They are uncharged electromagnetic radiation,

v. Hence, marks are found at the three places on the photographic plate.

2. The particles of powder are given an electric charge while spraying them to form the powder coating. Explain

Ans i. Powder coating is a method of applying a layer harder than paint on the surface of an iron objects to prevent rusting.

ii. In this method, a polymer resin, a pigment and some other ingredients are melted, mixed, cooled and ground into a uniform powder.

iii. This powder is sprayed on the polished metal surface by electrostatic spray deposition(ESD).

vi. In this method, the particles of the powder are given electrostatic charges due to which a uniform layer of the powder sticks to the metal surface.

v. Then the object is heated in the oven along with the coating. A chemical reaction occurs in the layer, resulting in the formation of long cross-linked polymer chains.

vi. This powder coating is highly durable, hard and attractive.

Q.16. Attempt the following. 9

1. Answer the following question:

1.What is baking soda? Give its chemical name and molecular formula.

1. state two use of Blue Vitriol.

2. What is brine? What happens when 1/5 of this solution is evaporated?

Ans 1. Baking soda is a white non-crystalline powder.

Its chemical name is Sodium hydrogen carbonate or Sodium bicarbonate and its molecular formula is NaHCO₃.

3. Blue vitriol is used in the blood test for diagnosing anaemia.

Ans: In the Bordeaux mixture, slaked lime along with blue vitriol is used as a fungicide on fruits like grapes and water melon.

4. The 25% of aqueous solution of the salt is called saturated brine.

Ans: When 1/5 of this solution is evaporated the dissolved salt gets crystallized and salt gets separated from the solution.

5 i. What problems do you get after playing colours on Rang panchami? Why?

ii. Which colors will you use to prevent occurrence of these problems?

iii. What problem do you have in painting the house and furniture?

Ans i. Artificial colors are prepared from chemical s/dyes which are very dangerous.The red color in the dye contains high proportion of mercury in it. This poses risks like blindness, skin cancer, asthma, itching of the skin, permanent blocking of sweat pores etc.

ii. To prevent occurrence of these problems natural colors prepared from beet root, flowers of flame of forest, spinach, gulmohar should be used.

iii. On painting the house and furniture with artificial colors , we may get problems such as asthma, itching of skin, permanent blocking of sweat pores, This is because the colors contain a high proportion of mercury in it.

6. Complete the table:

(Very High, Low, Very Low)

	Alpha Rays	Beta Rays	Gamma Rays
Ionization Potential	…………..	…………..	…………..
Power to Produce Fluorescence	…………..	…………..	…………..

Ans:

	Alpha Rays	Beta Rays	Gamma Rays
Ionization Potential	Very High	Low	Very Low
Power to Produce Fluorescence	Very High	Very Low	Low

Q.17. Complete the sentences in paragraph 9

1. Complete the paragraph.

(iridium-192, hyperthyroidism, Strontium – 90, phosphor, polycythemia, samarium-153, tritium, cobalt – 60)

The radioactive substances radium, promethium, …………………… with some are used to make

certain objects visible in the dark. The radioactive isotope ………………… to prevent their sprouting.

………………….. is used as a tracer in the research on various crops. Phosphorus – 32 is used in the treatment of …………………. . Iodine – 123 is used in the treatment of …………………….

Ans The radioactive substances radium, promethium, tritium with some phosphor are used to make certain objects visible in the dark. The radioactive isotope cobalt – 60 to prevent their sprouting. Strontium – 90 is used as a tracer in the research on various crops. Phosphorus – 32 is used in the treatment of polycythemia. Iodine – 123 is used in the treatment of hyperthyroidism.

2. Complete the paragraph.

(0.000458 u, alpha, 100, beta, -1, low, 0.000548 u, light. air)

Beta rays consist of a current of beta (e) particles. It has a charge of ……………….. and a mass of

…………………. Its velocity is 1/5 to 9/10 times the velocity of Beta rays are negatively charged

particles and hence they are attracted towards positively charged plate in an electric field. It has the ability to penetrate an aluminium sheet of thickness 2 mm which is ……………….. times the penetration of

………………… particles. It has ionization power and low power to produce fluoroscence.

Ans Beta rays consist of a current of beta (e) particles. It has a charge of -1 and a mass of 0.000548 u. Its velocity is 1/5 to 9/10 times the velocity of light. Beta rays are negatively charged particles and hence they are attracted towards positively charged plate in an electric field. It has the ability to penetrate an aluminium sheet of thickness 2 mm which is 100 times the penetration of alpha particles. It has low ionization power and low power to produce fluoroscence.

3. Complete the paragraph:

(natural, artificial, beta, gamma, cobalt-60, arsenic-74, iridium-192, strontium-90)

Certain elements such as uranium, thorium, radium, etc., spontaneously emit invisible, highly penetrating and high energy radiation. Such elements are called radioactive elements and this property is called radioactivity. The radioactive elements produced in the nuclear fission processes brought about in the laboratory by bombardment of particles are called radioactive elements. There are many practical applications to

the use of radiation and radioactive elements. These are used in scientific research, to diagnose and treat diseases and in various industries. …………… is used as a tracer in the research on various crops. is

used in food preservation. Iodine-123 is used in the treatment of hyperthyroidism. is used in the

detection of small tumours in the body. The …………… rays emitted by cobalt-60 and are used in

radiography camera, which is used for detecting flaws in metal work.

Ans Certain elements such as uranium, thorium, radium, etc., spontaneously emit invisible, highly penetrating and high energy radiation. Such elements are called radioactive elements and this property is called radioactivity. The radioactive elements produced in the nuclear fission processes brought about in the laboratory by bombardment of particles are called artificial radioactive elements. There are many practical applications to the use of radiation and radioactive elements. These are used in scientific research, to diagnose and treat diseases and in various industries. Strontium-90 is used as a tracer in the research on various crops. Cobalt-60 is used in food preservation. Iodine-123 is used in the treatment of hyperthyroidism. Arsenic-74 is used in the detection of small tumours in the body. The gamma rays emitted by cobalt-60 and iridium-192 are used in radiography camera, which is used for detecting flaws in metal work.

Q.18. Answer the following 27

1. When is the nucleus said to be unstable?

Ans i. In atom, of an element, the balance of protons and neutrons in the nucleus determines whether a nucleus

will be stable or unstable.

ii. Too many protons or neutrons upset this balance disrupting the binding energy from the strong nuclear forces making the nucleus unstable.

iii. Generally the elements with atomic numbers from 82-92 are found to be radioactive in nature.

2. What type of colors will you use to celebrate eco-friendly Rang Panchami? Why?

Ans i. Artificial colors are prepared from chemicals/dyes which are very dangerous.

1. The red color in the dye contains high proportion of mercury in it.
2. This poses risks like blindness, skin cancer, asthma, itching of the skin, permanent blocking of sweat pores etc.
3. Therefore it is necessary to use eco-friendly colors prepared from natural resources such as beet root, flowers of fame of forest, spinach, gulmohar.

3. What are the important substances that we use in day to day life? For what purpose do we use them?

Ans i. We use various substances in our day to day life like.

ii. Water : an universal solvent and an important constituent for our survival.

iii. Toothpaste: for cleaning teeth and maintaining hygiene.

iv. Soap : for bathing.

v. Clothes made from natural and artificial fibers.

vi. Vegetables, fruits and grains which provide the necessary nutrients to the body.

vii. Salts obtained from various sources for maintaining the balance in the body.

4. State and explain types of deodorants.

Ans Types of deodorants:

a. Ordinary deo: It contains a smaller proportion of aluminium. It decreases the odour of sweat.

b. Antiperspirant deo: This decreases the extent of sweating. It contains about 15% of aluminium chlorohydrate. It clogs the sweat pores on the skin.

c. Clinical deo: some people sweat heavily and it has harmful effects on the skin. Clinical deo is meant for such people. It contains about 20 to 25% aluminium. It is used during the night.

5. What is porcelain? How is it made?

Ans i. Porcelain is a hard, translucent and white colored ceramic.

ii. It is made by using the white clay called kaolin, found in China. Glass, granite and the mineral feldspar is mixed with kaolin and kneaded with water.

iii. The resulting mixture is shaped and fired in a kiln at a temperature of 1200 to 1450⁰C.

iv. On firing again after glazing, beautiful articles of porcelain are obtained.

6. How are ceramic articles made?

Ans i. When clay is kneaded in water, shaped and then fired in a kiln at a temperature of 1000 to 1150⁰C, a porous ceramic is formed.

ii. To overcome the porosity the fired objects are covered with finely ground glass powder suspended in water and is then fired again.

iii. As a result, the surface of the ceramic becomes shiny and its porosity disappears.

7. How is it determined whether a substance is acidic, basic or neutral?

Ans i.. pH of a solution varies from 0 to 14 in accordance with the strength of the solution. (acids or bases)

ii. The pH scale shows different colors at different values of pH.

iii. The given solution is acidic if the pH scale is from 0 to 6

iv. The given solution is neutral if the pH scale is 7

v. The given solution is basic if the pH scale is from 8 to 14.

8. Write briefly about the method of electrolysis of sodium chloride.

Ans

I. When an electrical current is passed through a saturated solution of sodium chloride(brine), it is electrolyzed and hydrogen gas is released at the cathode while chlorine gas is released at the anode along with formation of sodium hydroxide in the cell.

2NaCl + 2H₂O → 2NaOH + Cl₂ ↑ + H₂ ↑

ii. Sodium Water Sodium Chlorine Hydrogen Chloride Hydroxide Gas Gas

iii. When the salt is heated to a high temperature ( about 800⁰C), it melts. This is called the fused state of the salt.

iv. When fused salt is electrolyzed, chlorine gas is released at the anode and the liquid sodium metal, at the cathode.

9. Why has the use of methods like Teflon coating become more common?

Ans Teflon coating became more common because of following properties of Teflon.

i.The atmosphere and chemical substances have no effect on Teflon.

ii.Neither water nor oil will stick to Teflon coated articles.

iii.High temperatures do not affect Teflon as its melting point is 327⁰C.

iv. Teflon coated articles are easy to clean.

Q.19. Extra data (Not to be Use) 20

1. What are the constituents of baking powder? Where is the baking powder used?

Ans i. Baking powder consist of Sodium bicarbonate and tartaric acid.

ii. Baking powder is a leavening agent and is used for increasing the volume and lightening the texture of baked goods.

2. How are the various substances in day to day use classified from the scientific point of view?

Ans The various substances are classified as elements, compounds, mixtures, metals, non-metals, acids, bases and salts from the scientific point of view.

3. Sodium bicarbonate (Baking soda)

Ans i. Sodium bicarbonate is a white non crystalline powder.

ii. It is basic in nature as it turns moist red litmus paper blue.

4. Washing soda

Ans i. . Washing soda is a whitish and odourless powder at room temperature.

ii. Red litmus turns blue in color in its aqueous solution.

iii. It is hygroscopic, that is it absorbs moisture if left exposed to air.

Q. 20. Answer the following in detail 20

1. What is meant by water of crystallization? Give examples of salts with water of crystallization and their uses.

Ans i. The exact number of water molecules which are chemically bonded to a molecule of a salt within a hydrated crystalline compound is called as water of crystallization.

ii. Some substances in our daily use which contain water of crystallization are

iii. Alum ( Potash alum) – K₂SO₄.Al₂(SO₄)_3. 24H₂O

It is used in the process of water purification because of the property of coagulation, the solid impurities in water come together, become heavy and settle to the bottom. As a result, water above become clear

iv. Epsom salt ( Magnesium sulphate MgSO₄.7H₂O)

To grow better vegetables, a tablespoon of Epson salt is added to the soil below to boost growth.

v. Barium chloride ( BaCl₂.2H₂O)

1. It is used in hardening of steel 2. it is used in the manufacture of pigments.

vii. Sodium sulphate ( Glauber’s salt Na₂SO₄. 10 H₂O)

1. It is used as a laxative

viii. Blue Vitriol (Copper sulphate-CuSO_4. 5H₂O)

A.. It is used in blood test for diagnosing anaemia.

b. In the Bordeaux mixture, slaked lime along with blue vitriol is used as a fungicide on fruits like grapes and water melon

2. Write about artificial food colors, the substance used in them and their harmful effects.

Ans i. Food colors are substances that are added to make the food more attractive.

ii. Food colors are mixed in most soft drinks and foodstuffs available in the market. These food colors are in the form of gels, powder and pastes.

iii. Food colors are used in domestic as well as commercial products.

iv. Food colors are found added to packaged meat, chilli powder, turmeric, sweets and other similar substances so as to give them a good color.

3.

Ans

	Original color (of the solution)	Color on addition of universal indicator	pH value
Salt				Nature
Table salt	Colorless	Green	7	Neutral
				Alkaline (Basic)
Soap	White	Blue	9
Washing soda				Alkaline (Basic)
	White	Dark Blue	11
Baking soda				Alkaline (Basic)
	White	Dark green	8
Baking powder				Alkaline (Basic)
	White	Dark green	8
POP	White	Green	7	Neutral

V. Food colors are added to pickles, jam and sauce contain small quantities of lead and mercury.

vi. Over- consumption of artificial food colors can be harmful to health.

Vii. Diseases like ADHD( Attention Deficit Hyperactive Disorder) can affect children due to excessive consumption of foods with added food colors.

	Original color (of the solution)	Color on the addition of universal indicator
Salt			pH value	Nature
Table salt	Colorless	Green	7	Neutral
				Alkaline (Basic)
Soap	……………	Blue	……………
Washing soda
	White	……………	11	……………
Baking soda
	……………	Dark green	……………	……………
Baking powder				Alkaline (Basic)
	White	……………	8
POP	White	Green	……………	……………

4. Where in the industrial field is the radioactivity used?

Ans i. Radiography:

Internal cracks and voids in cast iron articles and iron solder can be detected with the help of gamma rays. For this purpose, isotopes like cobalt-60, iridium-192 are used in the radiography cameras. This technique is used for detecting flaws in the metal.

ii. Measurement of thickness, density and level:

It is necessary to maintain the required thickness in the manufacture of aluminium, plastic, iron sheets of differing thickness. In the manufacturing process, a radioactive substance is placed on one side and an instrument to measure radiation on the other. The radiation read by the measuring instrument varies with the thickness of the sheet. Material inside a packing can also be examined by the same technique.

iii. Luminescent paint and Radio luminescence:

Radioactive substances like radium, promethium, tritium with some phosphor are used to make certain objects visible in the dark (for example – hands of the clock). Krypton-85 is used in HID (high intensity discharge) lamps.

iv. Use in Ceramic tiles:

Luminous colors are used to decorate ceramic tiles, utensils, plates, etc.