Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 447 sodium hydroxide or potassium hydroxide. The process by which soap is prepared is called saponification. During saponification, sodium chloride is added in the solution to bring the soap in precipitation because sodium chloride increases the ionic product and decreases the solubility product. Soap having less density floats on the surface of the solution. Now it is collected and kept into moulds to get the soap cakes. Sodium carbonate or starch is added to make the soap hard. Different types of perfumes, colors, antiseptics and bleaching materials are also added in the soap. Detergents Detergents are synthetic petrochemicals obtained from hydrocarbons which are more soluble than soap. For example: Sodium lauryl sulphate, alkyl benzene sulphonate, sodium pyrophosphate, etc. Detergents are sodium salts of long chain benzene sulphonic acid, which are mostly nonbiodegradable with more cleansing property. A detergent is one of the cheap and popular cleansing agents made from hydrocarbons of petroleum by-products. Detergent is also called soapless soap because it has cleansing property like a soap but does not contain the chemicals that are found in the soap. Owing to the following reasons detergents are better than soap. 1. Synthetic detergents have a stronger cleansing action than that of soap. 2. They can be used even with hard water but soap is insoluble in it. 3. Synthetic detergents are prepared from the hydrocarbons as petroleum by-products. So, they are cheaper than soap. 4. Hard water having large amounts of calcium and magnesium ions gives insoluble precipitate, i.e., scum with soap but not with detergent. Detergent powders or washing powders are synthetic powders which contain synthetic detergents (15 – 30%), sodium carbonate, sodium silicate, sodium sulphate and a little amount of bleaching agents like sodium perborate. To make more popular and attractive, perfumes are also added in those powders. Differences between Soaps and Detergents S.N. Soaps S.N. Detergents 1. Soaps are sodium salts of higher fatty acids, e.g., sodium palmitate. 1. Detergents are sodium salts of long chain benzene sulphonic acid, e.g., sodium pyrophosphate . 2. Soaps are insoluble in hard water. So, they have less cleansing action. 2. Detergents are soluble in hard water. So, they have more cleansing action. 3. They are mostly biodegradable. So, they do not cause water pollution. 3. They are mostly non-biodegradable. So, they cause water pollution. 4. They are prepared from the fat of animals or plants. 4. They are prepared from petroleum byproducts. Effects of excessive use of detergents Detergents don't completely biodegrade. Detergents from the laundry make their way from the washing machine to groundwater. This water eventually ends up in the ground and in
448 cHemicalS uSed in daily life Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur waterways. The detergents contaminate fresh water supplies, rivers, and oceans with toxic heavy metals like cadmium, arsenic, phosphate, etc. Phosphates in detergents can lead to freshwater algal blooms. These algae release toxins and deplete oxygen in water. When the algae decompose, they use up the oxygen available for aquatic life. Phosphate tends to inhibit the biodegradation of organic substances. Detergents change pH of the soil and water, reduces light transmission, and increasing salinity in water sources. Chemical Pollution The pollution created by unwanted and excessive use of chemical substances is called chemical pollution. The different types of useful and useless chemicals which are obtained from organic and inorganic substances like fertilizers, insecticides, soaps, detergents, plastics, fibers, etc. are polluting the environment everyday. So, contamination by unwanted chemicals in the environment is called chemical pollution. Causes of chemical pollution Various factors are directly and indirectly involved in chemical pollution. Among them, some major factors are: i. The use of insecticides and fertilizers : Chemical fertilizers and insecticides constitute major chemical pollutants. These chemicals cause water, air and soil pollution. Most of them are non-biodegradable, so their effect remains for a long time. Insecticides like DDT cause water, air and soil pollution. Our environment has also been polluted by toxic insecticides like aldrin, dieldrin and heavy metals like lead, cobalt, mercury, etc. Nitrogenous fertilizers, when washed by rainwater, reach the water body. Due to the presence of nitrogen element, aquatic plants develop more rapidly and reduce oxygen concentration of water. Thus, aquatic animals die due to more BOD (Biological Oxygen Demand) value. ii. Household wastes and plastics : Different types of solid wastes of food, vegetables, clothes, ceramics, detergents, soaps, plastics, etc. also cause chemical pollution. The non-biodegradable nature of some chemicals like plastics, detergents, etc. is creating a severe problem in the environment. So, it is necessary to recycle plastics in order to avoid pollution by plastic materials. FACTS WITH REASONS Why is plastic considered the major cause of chemical pollution? Plastics are considered the major cause of chemical pollution becuase plastics are non-biodegradable substances which remain on the earth's surface for a long time without decomposing. When plastic is thrown everywhere, it causes environmental pollution. When plastics are burnt, they emit poisonous gases, which affect the health of living organisms. Environmentalists call for avoiding the use of plastics. Why? Plastic is a non-biodegradable substance which remains on the earth's surface for a long time without decomposing. When plastic is thrown everywhere, it causes environmental pollution. When plastics are burnt, they emit poisonous gases which affect the health of living organisms. So, environmentalists have called for avoiding the use of plastics.
Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 449 iii. Smoke from vehicles and factories : The products of combustion like carbon dioxide, carbon monoxide, sulphur trioxide, etc. are the major air pollutants. These gaseous pollutants come from industries and vehicles. When these gases combine with water, they give different types of acids like sulphuric acid, nitric acid, carbonic acid, etc. They come down in the form of rain called acid rain. Acid rain damages plants, animals, soil, etc. Carbon dioxide, methane, ozone, etc. also result in the greenhouse effect, which ultimately causes global warming. iv. Coloring materials of foodstuff : To attract customers as well as users, different types of colors are used in foodstuffs. All the colors are made from chemical compounds. Most of these compounds harm our health directly or indirectly and cause short-term or long-term effects. v. Dyes and detergents : Dyes like peroxide, hypochloride, sodium hydroxide and other bleaching agents, which are released from different industries like leather, textile, carpet, etc. also cause chemical pollution. They destroy the natural quality and composition of water. Detergent is another non-biodegradable cleansing agent, which remains in water for a long time and makes water unsuitable for drinking. vi. Metallic particles : Automobiles and industries release different types of metallic particles like lead, chromium, cadmium, mercury, arsenic, etc. When human beings, animals, birds and fishes inhale these metals, directly or indirectly, they suffer from various diseases. Control of chemical pollution Chemical pollution can be minimized or controlled in the following ways: i. Population growth and over urbanization should be controlled. ii. The overuse of insecticides and chemical fertilizers should be avoided. iii. Production and use of non-biodegradable substances should be discouraged. iv. Solid wastes like plastics, clothes, glasses, carpets, ceramics, etc. should be managed in a proper way. v. Use of colors, dyes in foodstuffs should be stopped. vi. Toxic gases which are released by industries should not be allowed to mix in the air. vii. Industries should be located away from a human settlement. viii. People should be made aware of chemical pollution and its effects. ix. Municipality should ban plastics, harmful pesticides etc. It should arrange vehicles to collect waste from city. Waste should be separated based on nature. Degradable waste should be made into compost. Other waste should be reduced, reused and recycled or disposed properly in landfill or incinerated. Ways to Get Rid of Chemical Pollution Plastics are the main agents of chemical pollution. We should use chemical fertilizers only after testing soil. The waste materials produced from industries and automobiles should be disposed properly. The harmful gases released from industries and automobiles should be changed into harmless gases before releasing them into the atmosphere. Household biodegradable wastes should be used to produce compost manure. We should be careful Smoke from industries
450 cHemicalS uSed in daily life Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur while using insecticides and pesticides. We should use edible colors in food items. These activities help to reduce environmental pollution caused by different chemical substances. Environmental impact of dichloro diphenyl trichloroethane(DDT) i. DDT is a very fine powdered insecticide. So, it causes air, water and soil pollution. ii. It lasts longer in the environment. So, it decreases population of the birds. iii. DDT when deposited in the lung of animal causes lung diseases. iv. It is deposited on the surface of leaves, which reduces the rate of photosynthesis and transpiration. HOT SKILL HIGHER ORDER THINKING SKILL 1. Many people use the swimming pool every day. They can spread germs in the pool. How is the pool kept clean and germ-free? Many people use the swimming pool every day. It is likely to have lots of germs. The pool must be kept clean and germ-free. The following methods are used to kill germs: i. Water is pumped through a filter to remove solid wastes. ii. Chlorine is added to get rid of algae and bacteria. Chlorine is frequently added to swimming pools because it reacts with water to create an acid that can eradicate bacteria, protists, and other microorganisms. 2. In case, soap and detergent are not available, World Health Organization has suggested that people should use wood ash as a cleaning agent. Why? In case, soap and detergent are not available, people are suggested to use wood ash as a cleaning agent by WHO. The reason is it is antibacterial. It also produces lye (sodium hydroxide). It can be used to wash hands and dishes. 3. Ramesh has a vegetable farm. Due to the lockdown, he could not sell his vegetables such as spinach, radish etc. What can he do to prevent food spoilage? Ramesh has a vegetable farm but he could not sell it due to the lockdown. To prevent food spoilage, he can do the following things. i. Vegetables can be stored in a refrigerator or cold storage. ii. Vegetables can be sliced into tiny pieces, dried and stored. iii. Vegetables such as radishes, tomatoes, cauliflower and mushroom can be pickled. iv. Green vegetables can be dried and stored or pickled. 4. Antioxidants are effective to preserve food. However, countries such as Australia, Canada and Japan have banned BHA antioxidants. Antioxidants are very effective to preserve food but it is banned in many countries. For example, BHA antioxidant is banned in Australia and Japan. The reason is some antioxidants are harmful to human health: i. It can cause faster ageing. ii. It can cause cancer. iii. It can be allergic to some people.
Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 451 5. How does DDT destroy the ecosystem? DDT is a very deadly poison. It is non-biodegradable. It kills any life that comes into its contact. Hence it destroys the ecosystem. 6. Common salt is added during saponification. Common salt is added during saponification so that the solubility of soap decreases. As a result, it will be easy to collect soap from the mixture. 7. Pickled spinach last for many days. Why? Pickled spinach lasts for many days because its acidic environment reduces microbial activity. 8. Farmers used chemical insecticides too much. The soil is too acidic and infertile now. How can farmers prevent such harmful effects of chemical insecticides now? Give a few suggestions. If overuse of chemical fertilizer has increased the acidity of the soil, and many harmful effects are observed in soil, crops and the surrounding environment, farmers should do the following things: i. use compost fertilizer in the fields instead of chemical fertilizer to reduce acidity. ii. reduce the use of chemical insecticides and increase the use of bio-insecticides. iii. grow leguminous plants in the fields at regular intervals. iv. test the pH value of the soil and use a required chemical to balance the pH value of the soil. 9. How does solid waste pollute our surrounding? How can such pollution be well managed to reduce its impact on the environment? Plastic, glass, iron scraps, cardboard, ceramics, cement, fibres, vegetables etc. are some solid wastes. They are one of the major causes of environmental pollution. i. solid wastes mix in water and pollute it. ii. some of the solids decompose and spread germs and foul smell in the surrounding. iii. solid waste makes the surroundings ugly. Pollution from solid waste can be managed in the following way: i. First of all, we should reduce the production of waste. ii. We should reuse waste if possible. iii. We can separate degradable waste from non-biodegradable waste. iv. Biodegradable waste can be used to make compost. Or we can keep it until the municipality collects it. v. Non-biodegradable waste especially metals, batteries, plastic etc. can be sold to kawadi. They visit the community regularly. Otherwise, we can keep it until the municipality collects it. vi. We should give the waste to the municipality. They will collect it, separate it, dump it in a landfill or incinerate it. 10. What do food preservatives do to bacteria? Food preservatives usually control the moisture of food, prevent the reproduction of bacteria and sometimes kill bacteria. As a result, food won't spoil.
452 cHemicalS uSed in daily life Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur 3 STEPS 3 STEPS EXERCISE EXERCISE STEP1 1. Choose the best answer from the given alternatives. a. Which of the following is a traditional food preservative? i. turmeric ii. benzoates iii. antioxidant iv. BHA b. Why is vitamin C added to canned food? i. it kills bacteria ii. to supply vitamins to people iii. it makes food tasty iv. it prevents oxidation c. Why should we not spill agrichemical? i. it is expensive so we must not waste it. ii. it is poisonous, it can kill children, people and cattle. iii. it is rare material and hard to find. iv. it makes the floor dirty d. Why is lemon juice one of the best natural cleaning agents? i. it is a cheap cleaning agent. ii. it is sour and soluble. iii. it is easy to use. iv. it kills bacteria and removes stains. e. Which one is chemical insecticides? i. triple super phosphate ii. urea iii. dieldrin iv. sodium chloride f. What is sodium oleate? i. soap ii. detergent iii. insecticide iv. food preservative 2. Define the following terms with required examples. a. Food preservation b. Food preservatives c. Traditional food preservatives d. Synthetic food preservatives e. Antioxidants f. Calcium carbide g. Pesticides h. Non-biodegradable waste i. Rodenticides j. Traditional cleaning agents k. Synthetic cleaning agents l. Biodegradable waste 3. Answer the following questions in very short. a. Give two examples of traditional food preservatives and synthetic food preservatives. b. Write the names of any two antioxidants. c. Which food preservative can increase the chance of blood cancer? d. Write an example of a natural hair cleaning agent. e. What chemical is used to artificially ripen fruit?
Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 453 f. What is soap made from? g. What do DDT and BHC stand for? h. What is the raw material for detergent? i. What is a sodium salt of benzene sulphonic acid called? STEP2 4. Give reasons. a. Traditionally, Nepalese people are using spices, oils and hot chilli to preserve food. b. We should reduce the consumption of canned food and eat more fresh vegetables. c. Calcium carbide is banned by the government of Nepal. d. Honey is used as food preservative. e. Acid, detergent and other cleaning agents should be stored out of reach of children. f. Amla can be used to wash hair. g. Wooden ash can be used to wash clothes. h. Dry food last longer than moist food. i. Lemon juice is added to water for washing dishes and cleaning tiles. j. People prefer detergent over soap. k. People are more attracted to synthetic cleaner than natural cleaners. l. We should use soap instead of detergent. m. Detergent is called soapless soap. n. Artificial synthetic food colours should not be used. o. We should use degradable waste for composting. p. Chlorine is added to sewages. 5. Differentiate between the following. a. Synthetic food preservatives and traditional food preservatives b. Soap and detergent c. Bioinsecticides and chemical insecticides d. Biodegradable pesticide and non-biodegradable pesticide 6. Answer the following questions in short. a. Write down the importance of food preservatives. b. Yamba has grown lots of spinach. How can he preserve spinach for next season? c. How do synthetic preservatives help to prevent food spoilage? d. Write down the importance of synthetic food preservatives. e. How does fruit ripened using calcium carbide damage our health? f. Mukesh has bought urea fertilizer to use in fields. How should he store this agrichemical? g. What are the poisonous chemicals used in homes? What are they used for? h. Samira used wood ash to wash dishes. Does it work? Why? l. Rama spread salt, spread spices, smoked and sundried meat. What does it do to the meat? Why did she do it?
454 cHemicalS uSed in daily life Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur j. Nepal government used DDT widely in 1952 to fight malaria. However, DDT was banned later permanently. What could be the reasons? k. Write down the uses of detergent. How does it deteriorate environment? l. How does sun drying help to prevent food spoilage? m. How does vitamin C prevent food spoilage? n. Why are plastics considered a major cause of chemical pollution? Give two reasons. o. What are the effects of degradable solid waste on the environment? p. Write a short note on usefulness of sajeevan plant, reetha, wooden ash and pina. 7. Answer the following questions on the basis of the given figure. i. What is shown in the diagram? ii. How should it be stored? iii. Should we continue to use it or replace it with compost? Why? STEP3 8. Answer the following questions. a. How is food usually preserved in our homes nowadays? How was food traditionally preserved? b. What is the function of antioxidants? How does it work? c. How are fruits ripened artificially? Explain with an example. d. What are poisonous chemicals used in agriculture? How do they help us? Enlist their harmful effects. e. Bishal has bought some rodenticides to kill rats and some chlorine to add to sewage. What precautions should he take while transporting them from the market to home? f. Nikita is about to use rodenticides in her fields. What safety measures should she follow while using this poisonous chemical? g. Dishwashing soap is finished in the kitchen. Binita has heard that adding lemon juice to water helps to make utensils clean. Is it true? Why? How? h. Most people use detergent to wash clothes and floors. Excessive use of detergent is harmful to the environment. Discuss. i. How do the use of chemical insecticides and chemical fertilizer harm the environment? j. Enlist the pesticide based on target organism. Describe each of them. k. What are different types of insecticides based on nature of action? Enlist and describe each of them.