Science & Technology · Chapter 19

34 solved questions

Chapter 19: Chemicals used in Daily Life

Every question in this chapter, answered and explained — step-by-step solutions drawn live from the chapter library across 8 question sections.

Very Short Answer Questions10 Short Answer Questions8 Give Reason Questions4 Differentiate Between3 Long Answer Questions2 Diagram-Based Questions2 Application / Conceptual Questions2 Additional SEE Practice3

Very Short Answer Questions

1SEE Boardqb-q0

What are food preservatives?

Ans.Substances used to protect food from decaying caused by bacteria, yeast, and mold are called food preservatives, e.g. salt, sugar, sodium benzoate.

2SEE Boardqb-q1

What is saponification?

Ans.The process of making soap by the hydrolysis of vegetable oil or animal fat with alkali is called saponification.

3SEE Boardqb-q2

What is a pesticide?

Ans.A pesticide is a poisonous substance used to remove, destroy, kill, and control harmful pests from seeds, plants, animals, and human health.

4SEE Boardqb-q3

Write the full forms of DDT and BHC.

Ans.DDT = Dichlorodiphenyltrichloroethane. BHC = Benzene Hexachloride.

5SEE Boardqb-q4

Why is detergent called soapless soap?

Ans.Because it cleans clothes like soap but has a different chemical composition — it is not made from fatty acid salts like soap.

6SEE Boardqb-q5

Name two ripening agents used to ripen fruits.

Ans.Calcium carbide and ethylene gas are used as ripening agents.

7SEE Boardqb-q6

Name two first class food preservatives.

Ans.Sugar and salt are first class food preservatives.

8SEE Boardqb-q7

In which year was DDT first imported to Nepal, and for what purpose?

Ans.DDT was first imported to Nepal in 1952 AD to control malaria.

9SEE Boardqb-q8

Name one natural material used for cleansing hair.

Ans.Peena (mustard seed cake) is a natural material used for cleansing/strengthening hair.

10SEE Boardqb-q9

What is chemical pollution?

Ans.Chemical pollution is the degradation of the quality of environmental components (air, water, soil) due to chemicals, causing imbalance in the ecosystem.

Short Answer Questions

1SEE Boardqb-q10

What do you mean by food preservatives? Why are they used?

Ans.Food preservatives are substances used to protect food from decaying due to the growth of bacteria, yeast, and mold. They are used so that cereals, vegetables, fruits, meat, milk, and other food products can be stored for a long time without spoiling.

2SEE Boardqb-q11

What chemicals are used as food preservatives?

Ans.Sodium benzoate, sorbate, sulphur dioxide, nitrates and nitrites, BHA, BHT, calcium propionate, and sodium metabisulfite are used as chemical food preservatives.

3SEE Boardqb-q12

What are the natural methods used to preserve the nutrients of food?

Ans.Drying in sunlight, keeping food in cold places or above water, using wood ash, and mixing turmeric with oil are traditional natural methods; pasteurization, freezing, and keeping food in cold stores are modern natural preservation methods.

4SEE Boardqb-q13

What do you mean by natural food preservatives? Why are they good compared to chemical food preservatives?

Ans.Natural food preservatives come from organic matter such as plants, animals, fungi, and algae (e.g. mugwort, neem oil, lemon concentrate). They are considered better than chemical preservatives because they do not cause the health problems (skin irritation, respiratory issues) that overused chemical preservatives can cause, and they are more environmentally friendly.

5SEE Boardqb-q14

How can fruits be ripened artificially? Write methods and processes for it.

Ans.Fruits like mango and banana can be ripened artificially using ripening agents such as calcium carbide, ethylene gas, and ethephon, which are placed with the fruits (e.g. in a sachet) to speed up the natural ripening process. Traditional methods include wrapping fruits in jute sacs, using Asuro leaves, or burying them in soil-covered pits.

6SEE Boardqb-q15

What precautions should be taken while using chemical pesticides?

Ans.Buy only permitted pesticides on expert advice, read and follow label instructions, store them in airtight containers away from children and food, wear protective clothing (mask, gloves, goggles) while spraying, and wash hands and bathe immediately after use.

7SEE Boardqb-q16

Explain the soap-making process.

Ans.Vegetable oil is mixed with sodium hydroxide solution and heated; this forms a thick paste. A little salt (sodium chloride) is added to help separate the soap from the mixture. The mixture is then filtered — the residue on the filter paper is soap, which is poured into a mould and left to set. The remaining filtrate contains glycerin.

8SEE Boardqb-q17

What is detergent? Write its two examples. What effects are seen on human health and the environment due to the use of detergent?

Ans.Detergent is a soapless synthetic cleaning agent made from hydrocarbons, more soluble in water than soap. Examples: sodium lauryl sulphate, alkyl benzene sulphonate. Because detergent is non-biodegradable, its long-term use can cause skin irritation or burns, soil and water pollution, and fading of cloth colour.

Give Reason Questions

1SEE Boardqb-q18

Use of DDT powder causes imbalance in the ecosystem. Why?

Ans.DDT is a non-biodegradable, persistent pesticide that kills both harmful and useful insects. It pollutes water and soil, harms the reproductive systems of birds and fish (thin eggshells, fewer eggs), and remains in the food chain for a long time, thereby disturbing the balance of the ecosystem.

2SEE Boardqb-q19

The use of chemical pesticides should be decreased. Why?

Ans.Chemical pesticides pollute air, water, and soil, destroy useful microorganisms and insects, cause health problems like skin burns and respiratory disease in humans, and many of them (like DDT, aldrin) remain in the environment and food chain for a long time. Hence, their use should be reduced and safer alternatives like integrated pest management should be preferred.

3SEE Boardqb-q20

Salt is used in the process of making soap. Why?

Ans.Salt (sodium chloride) is added during soap-making to help separate the soap from the reaction mixture — it makes the soap coagulate and float as a solid crust, separating it from the glycerol and remaining liquid, which makes soap easier to filter and collect.

4SEE Boardqb-q21

Pickles can be preserved for a long time. Why?

Ans.Pickles are preserved by mixing them with salt and oil. Salt and oil act as food preservatives that control the growth of bacteria, yeast, and mold, which are responsible for food decay, so the pickle does not spoil for a long time.

Differentiate Between

1SEE Boardqb-q22

Differentiate between chemical pesticides and biological pesticides.

Chemical Pesticides	Biological Pesticides
Made using synthetic chemical compounds.	Made using living organisms or natural substances (e.g. neem oil, biological predators).
Often non-biodegradable; can persist in the environment and food chain.	Generally biodegradable and break down quickly without lasting harm.
Example: DDT, Malathion, Cypermethrin.	Example: Neem-based pesticide, biological pest predators.

2SEE Boardqb-q23

Differentiate between chemical food preservative and organic (natural) food preservative.

Chemical Food Preservative	Organic/Natural Food Preservative
Obtained by chemical derivation of compounds.	Obtained from natural organic sources like plants and animals.
Used only in limited amounts (second class preservative).	Can generally be used in necessary amounts (first class preservative).
Example: sodium benzoate, sulphur dioxide.	Example: salt, sugar, vinegar, honey, mugwort, neem oil.

3SEE Boardqb-q24

Differentiate between soap and detergent.

Soap	Detergent
Sodium or potassium salt of long chain fatty acids.	Chemical obtained from hydrocarbons.
Made by saponification of oil/fat with alkali.	Manufactured synthetically from petroleum-based chemicals.
Forms insoluble scum with hard water; less effective in hard water.	Works well even in hard water.
Biodegradable — does not cause chemical pollution.	Non-biodegradable — can cause chemical pollution.

Long Answer Questions

1SEE Boardqb-q25

Write about the pollution caused by industrial products like cement, glass, ceramics, plastic, fiber, chemical fertilizers, soap, and detergent. Write its causes and suggest proper ways for management.

Ans.Haphazard use and disposal of industrial chemicals such as cement, ceramics, glass, plastic, fiber, chemical fertilizers, soap, and detergent degrades the quality of air, water, and soil and causes imbalance in the ecosystem. This happens mainly because such waste is dumped directly into water sources, farmland, and open dumping sites without treatment.

2SEE Boardqb-q26

There has been excessive use of chemical pesticides in Hari's village, due to which complex problems have been observed in the health of people and the environment. What may be the alternatives to solve these problems? Give some suggestions.

Ans.The village should reduce dependence on chemical pesticides and follow integrated pest management, which combines biological, cultural, and minimal chemical methods.

Diagram-Based Questions

1SEE Boardqb-q27

Draw and label the soap-making process using a beaker, oil, NaOH, glass rod, and heat source.

Ans.Draw three beakers in sequence: (1) a beaker containing NaOH solution, (2) a beaker with oil and NaOH mixture being heated with a glass rod stirring it over a flame, (3) a beaker showing a separated soap crust layer floating above a glycerol layer. Label each part clearly (NaOH, oil-NaOH mixture, glass rod, heat source, soap crust, glycerol).

2SEE Boardqb-q28

Study a picture of a pesticide storage cabinet with warning labels ('Flammable', 'Pesticides') and answer: why must pesticides be stored this way?

Ans.Pesticides must be stored in a locked, clearly labelled, well-ventilated cabinet away from children and food because they are poisonous and often flammable; clear labelling and safe storage reduce the risk of accidental poisoning, fire, and leakage into the environment.

Application / Conceptual Questions

1SEE Boardqb-q29

A shopkeeper is ripening mangoes quickly using a white chemical sachet before selling them. What is this chemical likely to be, and what health risks does its overuse carry?

Ans.The chemical is most likely calcium carbide, a ripening agent. Its overuse can cause health problems such as skin irritation, skin burning, red blisters on the skin, lung effusion, and eye irritation, so consumers and sellers should be cautious about its use.

2SEE Boardqb-q30

A student washes clothes in hard water using ordinary soap and finds it does not lather well. What should the student use instead, and why?

Ans.The student should use a detergent instead of soap, because detergent works well even in hard water — unlike soap, which forms insoluble scum with hard water and becomes an inefficient cleaner.

Additional SEE Practice

1SEE Boardqb-q31

Why should aluminium phosphide (a fumigant pesticide) be used only in stored grain, not near people?

Ans.Aluminium phosphide produces poisonous gas/fumes on contact with air, which is highly toxic to humans if inhaled directly; it is meant to kill pests hidden inside stored agricultural products in a sealed space, so it should never be used in occupied or poorly ventilated areas.

2SEE Boardqb-q32

Which of the following is an example of a systemic pesticide: Malathion, Thiamethoxam, or Aluminium phosphide?

Ans.Thiamethoxam is an example of a systemic pesticide, as it is absorbed by plant roots/leaves and makes the whole plant poisonous to insects that feed on it.

3SEE Boardqb-q33

Why is it important to follow the waiting period mentioned on a pesticide label before harvesting or consuming sprayed crops?

Ans.Pesticide residues remain on and inside crops for some time after spraying. Following the recommended waiting period allows these residues to break down or reduce to a safer level before the crop is consumed, protecting human health.

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