Class 10 Science Lesson 19

Exercise

1. Choose the correct option for the following questions.

a) Why is detergent called a soapless soap?

i. It does not give lather with hard water as a soap.
ii. It has the same chemical composition as of soap.
iii. It has cleaning properties like soap and it can be used with hard water.
iv. It has cleaning properties like soap but its chemical nature is different.

Answer: iv. It has cleaning properties like soap but its chemical nature is different.

b) Identify the group of insecticides:

i. Potassium chloride, aldrin, benzene hexachloride
ii. DDT, sodium chloride, aldrin
iii. Dieldrin, DDT, methoxychloride
iv. Potassium chloride, aldrin, malathion

Answer: iii. Dieldrin, DDT, methoxychloride

c) In which group does sodium stearate lie?

i. Soap
ii. Detergent
iii. Insecticide
iv. Food preservative

Answer: i. Soap

d) What is the main use of detergents?

i. To clean hands and foot
ii. To take bath
iii. To wash clothes
iv. To clean toilet

Answer: iii. To wash clothes

e) Which of the following compounds is used to ripen fruits?

i. Calcium carbide
ii. Calcium carbonate
iii. Sodium sulphate
iv. Sodium carbonate

Answer: i. Calcium carbide

2. Write Differences Between:

a. Chemical Pesticides and Biological Pesticides

b. Chemical Food Preservative and Organic Food Preservative

c. Soap and Detergent

3. Give Reason

a. Use of DDT powder causes imbalance in the ecosystem.

Reason: DDT is non-biodegradable and accumulates in the food chain, harming birds, aquatic life, and other organisms, leading to ecological imbalance.

b. The use of chemical pesticides should be decreased.

Reason: Overuse of chemical pesticides causes soil and water pollution, harms beneficial organisms, and can lead to health problems in humans.

c. Salt is used in the process of making soap.

Reason: Salt helps in the precipitation of soap during the manufacturing process, allowing it to separate from the mixture.

d. Pickles can be preserved for a long time.

Reason: Pickles contain salt, oil, and vinegar, which inhibit the growth of microbes and act as natural preservatives.

4. Answer the following questions:

a. Write the full forms of DDT and BHC.

Answer:

• DDT – Dichloro Diphenyl Trichloroethane
• BHC – Benzene Hexachloride

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

Answer:
Food preservatives are substances used to prevent spoilage and microbial growth in food, thereby increasing its shelf life and maintaining its quality.

c. What chemicals are used as food preservatives?

Answer:

Examples of chemical food preservatives:

• Sodium benzoate
• Potassium metabisulfite
• Sorbic acid
• Sulphur dioxide

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

Answer:

Natural food preservation methods:

1. Drying (removes moisture)
2. Cooling/Refrigeration
3. Salting
4. Use of vinegar or lemon juice
5. Fermentation

e. What do you mean by natural food preservatives? Why are they good in comparison to the chemical food preservatives? Analyze it.

Answer:
Natural food preservatives are substances like salt, sugar, lemon juice, and vinegar that prevent spoilage without artificial chemicals.

Why they are better:

• Safer for health (non-toxic)
• Biodegradable and eco-friendly
• No harmful side effects like some chemical preservatives

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

Answer:

Artificial Ripening Methods:

1. Using Calcium Carbide – reacts with moisture to release acetylene gas, which acts like ethylene (a natural ripening hormone).
2. Using Ethylene gas or Ethephon sprays – controlled methods used commercially.

⚠ Note: Calcium carbide is harmful and banned in many countries.

g. What precautions should be taken while using chemical pesticides?

Answer:

Precautions:

1. Use recommended quantities only.
2. Wear gloves and masks during spraying.
3. Avoid spraying during windy days.
4. Wash fruits and vegetables before eating.
5. Store chemicals safely away from children and animals.

h. Make a list of chemicals used for cleaning purposes in your house and locality. Write the effects of these substances in the environment.

Answer: 

i. Explain the soap making process.

Answer:

Soap is made by the chemical reaction between a fat/oil and an alkali (usually sodium hydroxide or potassium hydroxide). This reaction is called saponification.

Steps:

1. Raw Materials:
   • Fats or oils (e.g., vegetable oil, animal fat)
   • Sodium hydroxide (NaOH) – caustic soda
   • Water
2. Procedure:
   • The fats/oils are heated with sodium hydroxide solution.
   • A chemical reaction occurs, producing glycerol and sodium salt of fatty acid (soap).
   • Common salt (NaCl) is added to separate soap from the mixture.
   • The soap is filtered, shaped, and dried.

Chemical Reaction: Fat/Oil+NaOH→Glycerol+Soap

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

Answer:

Detergents are synthetic cleaning agents made from petroleum products. They work effectively even in hard water.

Examples:

1. Sodium lauryl sulfate
2. Sodium dodecylbenzene sulfonate

Effects on Human Health and Environment:

Health Effects:

• May cause skin irritation or allergies
• Harmful if ingested
• Long-term exposure can affect respiratory system

Environmental Effects:

• Non-biodegradable detergents cause water pollution
• Harm aquatic organisms
• Lead to foam formation in rivers/lakes, blocking oxygen supply

Argument:
Though detergents are efficient cleaners, excessive and careless use harms both human health and ecosystems. Use of eco-friendly detergents is a better alternative.

k. There has been an 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.

Answer:

Problems:

• Soil and water contamination
• Health problems like skin diseases, respiratory issues
• Death of beneficial organisms

 Alternatives and Suggestions:

1. Use of biological pesticides (e.g., neem extract, Bacillus thuringiensis)
2. Integrated Pest Management (IPM) techniques
3. Crop rotation and organic farming
4. Raise awareness and training for farmers on safe pesticide use
5. Government regulation and monitoring

l. What do you mean by chemical pollution? What are its effects? Write practical ways to minimize it.

Answer:

Chemical pollution refers to the presence of harmful synthetic chemicals (like pesticides, industrial waste, fertilizers) in the air, water, and soil.

Effects:

• Water pollution: killing aquatic life
• Air pollution: respiratory issues in humans
• Soil degradation: loss of fertility
• Health issues: cancer, neurological damage

Ways to Minimize:

1. Use eco-friendly alternatives (organic fertilizers, natural pesticides)
2. Promote recycling and proper waste disposal
3. Install treatment plants in industries
4. Reduce the use of plastic and synthetic chemicals

Educate the public on chemical hazards

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

Answer:

Pollution by Industrial Products in Locality:

Causes:

• Cement: Dust and CO₂ emissions from factories
• Glass and Ceramics: High energy usage and chemical release
• Plastic and Fiber: Non-biodegradable waste in water and land
• Chemical fertilizers: Soil and water pollution
• Soap and Detergents: Water pollution and skin irritation

Effects:

• Air and water pollution
• Health hazards to people and animals
• Environmental degradation

Management Suggestions:

1. Strict regulation of industrial waste disposal
2. Encourage use of biodegradable alternatives
3. Set up waste treatment and recycling plants
4. Promote sustainable industrial practices
5. Raise awareness in the community