unit 19 Chemicals Used in Daily Life

1. Summary: Chemicals Used in Daily Life

2.1 Choose the correct options for the following questions:

2.2 Write differences between:

(a) Chemical pesticides and biological pesticides

S.N.	Chemical Pesticides	Biological Pesticides
1.	They are synthetically manufactured chemicals produced in laboratories or industries.	They are derived from natural materials like animals, plants, bacteria, and minerals.
2.	They are broad-spectrum, often killing beneficial insects along with pests.	They are usually target-specific and do not harm beneficial organisms (like bees or birds).
3.	They are generally non-biodegradable and leave harmful residues in the soil and food chain.	They are biodegradable and decompose quickly without leaving toxic residues.
4.	Their excessive use leads to the development of resistance in pests (pests become immune).	Resistance development in pests is very slow or negligible.
5.	They act very fast to show results.	They generally take a longer time to show effective results.
6.	Examples: DDT, BHC, Malathion, Aldrin.	Examples: Neem extracts, Bacillus thuringiensis (Bt), Trichoderma.

(b) Chemical food preservative and organic food preservative

S.N.	Chemical Food Preservative	Organic (Natural) Food Preservative
1.	These are artificial chemical substances added to food to prevent spoilage.	These are naturally occurring substances used to preserve food.
2.	They are produced industrially through chemical synthesis.	They are obtained from natural sources like plants and minerals.
3.	Long-term consumption may cause adverse health effects like allergies or toxicity.	They are generally safe for health and often add nutritional value to the food.
4.	They work by chemically inhibiting the growth of bacteria and fungi.	They often work by creating a physical barrier or changing the osmotic environment (e.g., removing moisture).
5.	Small quantities are usually sufficient for preservation.	Relatively larger quantities are often required for effective preservation.
6.	Examples: Sodium benzoate, Potassium metabisulphite, Sorbic acid.	Examples: Common salt, Sugar, Oil, Vinegar, Lemon juice.

(c) Soap and detergent

S.N.	Soap	Detergent
1.	Soaps are sodium or potassium salts of long-chain fatty acids (carboxylic acids).	Detergents are sodium salts of long-chain benzene sulphonic acids or alkyl hydrogen sulphates.
2.	They are prepared from natural fats and vegetable oils.	They are prepared from synthetic hydrocarbons obtained from petroleum or coal.
3.	Soaps do not lather well in hard water and form an insoluble white precipitate called scum.	Detergents lather well even in hard water and do not form insoluble scum.
4.	They are fully biodegradable and do not cause significant water pollution.	Some detergents (with branched chains) are non-biodegradable and cause water pollution.
5.	They have relatively weaker cleansing action compared to detergents.	They have a strong cleansing action.
6.	Example: Sodium stearate ($C_{17}H_{35}COONa$).	Example: Sodium lauryl sulphate.

2.3 Give reason:

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

Reason: DDT (Dichlorodiphenyltrichloroethane) is a non-biodegradable chemical pesticide. When used, it does not decompose and remains in the environment for a long time. It enters the food chain through water and crops and accumulates in the bodies of organisms (biomagnification). It kills not only harmful pests but also beneficial insects, birds, and aquatic life, disrupting the natural food web. This indiscriminate killing and long-term persistence cause a severe imbalance in the ecosystem.

(b) The use of chemical pesticides should be decreased.

Reason: The use of chemical pesticides should be decreased because they cause environmental pollution (soil, water, and air). They leave toxic residues on fruits and vegetables that can cause serious health issues in humans, such as cancer and respiratory problems. Furthermore, overuse kills beneficial organisms (like earthworms and bees) and reduces soil fertility. Reducing their use promotes sustainable agriculture and protects public health.

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

Reason: Common salt (Sodium Chloride) is added during the soap-making process to separate the soap from the mixture. This process is called “salting out.” The addition of salt decreases the solubility of soap in water. Due to the common ion effect, the soap precipitates out as a solid, floating on the top, while the glycerol and impurities remain in the solution.

(d) Pickles can be preserved for a long time.

Reason: Pickles are preserved for a long time because of the addition of salt, oil, and spices. Salt acts as a preservative by drawing water out of microbial cells through osmosis (plasmolysis), which kills bacteria or inhibits their growth. Oil forms a protective layer on top of the pickle, cutting off the supply of oxygen (air). Since most spoilage-causing microorganisms (aerobic bacteria and molds) need air and moisture to grow, these conditions prevent spoilage.

2.4 Answer the following questions:

(a) Write the full forms of DDT and BHC.

Answer:

DDT: Dichlorodiphenyltrichloroethane

BHC: Benzene Hexachloride (also known as HCH or Hexachlorocyclohexane)

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

Answer: Food preservatives are chemical or natural substances added to food items to prevent or delay their spoilage caused by microorganisms (bacteria, fungi, yeast) or chemical changes (oxidation).

They are used to:

• Increase the shelf life of food products.

• Retain the nutritional value, flavor, and texture of food for a longer period.

• Prevent food poisoning by inhibiting the growth of harmful pathogens.

• Make seasonal food available throughout the year.

(c) What chemicals are used as food preservatives?

Answer: Common chemicals used as food preservatives include:

• Sodium benzoate: Used in jams, jellies, and soft drinks.

• Sodium meta-bisulphite: Used in preserved fruits and dried foods.

• Potassium sorbate: Used in dairy products and baked goods.

• Acetic acid (Vinegar): Used in pickles and sauces.

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

Answer: The natural methods used to preserve food nutrients include:

• Drying (Dehydration): Removing moisture from food (e.g., drying grains, methi) to stop microbial growth.

• Salting: Coating meat or fish with salt to draw out moisture.

• Sugaring: Using high sugar concentration (e.g., in jams) to inhibit bacteria.

• Refrigeration/Freezing: Storing food at low temperatures to slow down enzymatic activity and bacterial growth.

• Smoking: Exposing meat or fish to smoke, which dehydrates and adds antimicrobial compounds.

• Canning/Vacuum Packing: Sealing food in airtight containers to prevent re-contamination.

(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 ingredients derived from nature, such as salt, sugar, oil, spices, vinegar, and lemon juice, which prevent food spoilage without the use of synthetic chemicals.

Analysis: They are considered better than chemical preservatives because:

• Safety: They are generally non-toxic and have no harmful side effects on human health, whereas chemical preservatives (like nitrates) can be carcinogenic or cause allergies in the long run.

• Nutrition: Many natural preservatives (like lemon juice or oil) add nutritional value or essential fats/vitamins to the diet, unlike synthetic additives.

• Flavor: They enhance the natural taste of the food, whereas chemicals might alter the taste or require masking agents.

• Eco-friendly: They are biodegradable and sustainable.

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

Answer: Fruits can be ripened artificially using specific chemical agents that accelerate the ripening process.

Methods and Process:

1. Using Calcium Carbide: This is a common (though often banned/restricted) method. Calcium carbide is wrapped in paper and placed inside crates of unripe fruits (like mangoes or bananas). It reacts with the moisture in the fruit to release Acetylene gas.

Reaction: $CaC_2 + 2H_2O \rightarrow C_2H_2 (Acetylene) + Ca(OH)_2$

Acetylene generates heat and mimics the natural ripening hormone, causing the fruits to ripen and turn yellow quickly.

2. Using Ethylene Gas: This is the safer, modern method. Fruits are exposed to ethylene gas in controlled chambers, or ethephon solution is used, which releases ethylene. Ethylene is a natural plant hormone that triggers ripening safely.

(g) What precautions should be taken while using chemical pesticides?

Answer: Precautions to be taken include:

• Protective Gear: Always wear masks, hand gloves, goggles, and full-sleeved clothing to prevent inhalation or skin contact.

• Label Reading: Read the instructions, expiry date, and toxicity level on the label carefully before use.

• Wind Direction: Do not spray against the direction of the wind to avoid the chemical blowing back onto the sprayer.

• Hygiene: Wash hands and face thoroughly with soap and water after spraying. Wash the clothes used during spraying separately.

• Storage: Keep pesticides in a locked cabinet, away from food items and out of reach of children.

• Harvesting Gap: Wait for the recommended period (safety interval) after spraying before harvesting and consuming the crops.

(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: List of cleaning chemicals:

• Soaps (Bathing and laundry soap).

• Detergents (Washing powder, liquid detergent).

• Phenol/Phenyl (Floor cleaners).

• Acid (Toilet cleaners like Hydrochloric acid).

• Glass cleaners (containing Ammonia).

• Bleaching powder.

Environmental Effects:

• Water Pollution: Detergents containing phosphates cause eutrophication (excessive algae growth) in water bodies, which depletes oxygen and kills aquatic life.

• Soil Pollution: Non-biodegradable components accumulate in the soil, affecting soil microorganisms and fertility.

• Toxicity: Strong acids and alkalis alter the pH of water sources, harming fish and other aquatic organisms.

(i) Explain the soap making process.

Answer: The process of making soap is called Saponification.

Process:

1. Raw Materials: Vegetable oil (like coconut, mustard, or olive oil) or animal fat, Sodium Hydroxide (NaOH – Caustic Soda), Water, and Common Salt (NaCl).

2. Heating: The oil is taken in a beaker and heated gently.

3. Mixing Alkali: A solution of Sodium Hydroxide (NaOH) is added to the hot oil.

4. Reaction: The mixture is heated and stirred continuously. The oil reacts with the alkali to form soap (sodium salt of fatty acid) and glycerol.

Reaction: $Fat/Oil + Sodium Hydroxide \xrightarrow{Heat} Soap + Glycerol$

5. Salting Out: Common salt is added to the mixture. This precipitates the soap, making it separate from the solution as a solid.

6. Filtration/Moulding: The solid soap is separated, cooled, and poured into moulds to set into bars.

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

Answer: Detergent: Detergents are synthetic cleansing agents, chemically defined as sodium salts of long-chain benzene sulphonic acids or alkyl hydrogen sulphates. They have strong cleaning properties and work well in hard water.

Examples:

• Sodium lauryl sulphate.

• Sodium alkyl benzene sulphonate.

Effects (Argument):

On Environment: Many detergents contain phosphates and branched hydrocarbon chains. The phosphates act as fertilizers for algae, leading to eutrophication in ponds and rivers. This forms an algal bloom that blocks sunlight and depletes dissolved oxygen, causing the death of fish. Non-biodegradable detergents persist in water for years, foaming and polluting sources.

On Human Health: Detergent residues on clothes or dishes can enter the body. They may cause skin irritation, dermatitis, or allergic reactions. If ingested in small amounts over time (via water or plates), they can disrupt the digestive system or accumulate in the body.

(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: To solve the problems caused by excessive chemical pesticides, the following alternatives and suggestions should be adopted:

• Use Biological Pesticides: Encourage the use of bio-pesticides like neem oil, tobacco decoction, or Bacillus thuringiensis (Bt), which are safe for humans and the environment.

• Integrated Pest Management (IPM): Adopt IPM techniques which combine biological, physical, and limited chemical methods to control pests in an eco-friendly way.

• Organic Farming: Promote organic farming using compost and manure instead of chemicals.

• Natural Enemies: Introduce or protect natural predators of pests, such as ladybird beetles (which eat aphids) or birds.

• Crop Rotation: Practice crop rotation and mixed cropping to break the life cycle of pests naturally.

• Physical Methods: Use light traps or pheromone traps to catch insects instead of spraying chemicals.

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

Answer: Chemical Pollution: The contamination of the environment (air, water, and soil) by the release of harmful synthetic chemical substances from industries, agriculture, and households is called chemical pollution.

Effects:

• Health Issues: Causes respiratory diseases, cancer, skin disorders, and hormonal imbalances in humans.

• Ecosystem Damage: Destroys biodiversity, kills aquatic life, and makes soil infertile.

• Global Impact: Contributes to ozone layer depletion and global warming (greenhouse gases).

Practical Ways to Minimize:

• Reduce/Substitute: Use biodegradable and eco-friendly alternatives (e.g., paper bags instead of plastic, natural cleaners instead of strong acids).

• Waste Treatment: Industries must treat chemical waste (neutralization) before discharging it into water bodies.

• Recycling: Recycle plastics and other chemical products to prevent them from entering landfills.

• Proper Disposal: Do not throw batteries, electronics, or medicines in regular trash; use designated disposal centers.

• Strict Regulations: Enforce strict government laws on industrial emissions and pesticide use.

(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 from Industrial Products:

• Cement/Glass/Ceramics: Factories produce immense dust (particulate matter) and smoke, causing air pollution. This dust settles on leaves, blocking photosynthesis, and causes respiratory issues (like silicosis) in humans.

• Plastics/Fiber: These are non-biodegradable. They clog drains, cause soil pollution, and release toxic fumes (dioxins) when burned.

• Fertilizers/Soaps/Detergents: Runoff from fields and homes enters water bodies, causing chemical contamination and eutrophication (algal blooms).

Causes:

• Unfiltered smoke and dust emissions from factory chimneys.

• Direct discharge of untreated liquid waste (effluents) into rivers.

• Lack of public awareness regarding waste segregation and disposal.

• Overuse of chemical products in agriculture and daily life.

Ways for Management:

• Filtration: Industries must install electrostatic precipitators and filters to trap dust and harmful gases.

• Effluent Treatment Plants (ETP): All liquid chemical waste must be treated to remove toxicity before discharge.

• 3R Principle: Adopt Reduce, Reuse, and Recycle for plastics and glass.

• Green Belts: Plant trees around industrial areas to absorb dust and noise.

• Public Awareness: Educate locals about the harmful effects of burning plastic and overuse of detergents.