Oasis School Science and Technology - 10 451 restriction to use these food preservatives. Multiple second class food preservatives cannot be used together. It cannot be used in larger quantity otherwise it can cause health hazards. Reasonable Fact Canned food does not contain preservatives. Canned food does not contain preservatives because germs are killed by heating before they are packaged in an airtight container. Activity 1 Visit your grandparents. Try to find out how they store vegetables for winter when there were no refrigerators. 1. Natural food preservatives Certain spices, salts, sugar, and oil can be used to preserve food. Nepalese people have traditionally used a variety of substances to preserve food. Natural food preservatives are spices, oils, salts, sugar, chili, and other ingredients that have been used for centuries to preserve food. For example, Nepalese people often cut vegetables like radish and dry them in the sun. Then, these vegetables are combined with hot sauce, mustard oil, garlic, ginger, turmeric, Himalayan salt, and hot chillies. Food won't spoil for a very long time because these ingredients naturally kill bacteria. By using this technique, a vegetable can be properly preserved and kept for almost a year. Fig: pickled radish Fig: pickled carrot, turnip and cauliflower Fig: pickled mushroom To preserve meat, Nepalese people also use natural fats, oils, turmeric, etc. A paste made of turmeric, garlic, and other ingredients is used to polish the meat. Mustard oil or fat is applied to the meat. After that, it is smoked and given time to dry in the sun for a few days. The meat will be preserved for months. Fig: oiled, smoked and then dried meat
452 Oasis School Science and Technology - 10 Farmers also mix leaves from plants like titepate, neem, neem oil, timur, and aashuro into grains like paddy, wheat, and mustard before storing them. It helps to protect from dangerous insects like moths and wheat weevils (ghun). Food remains fresh for many months. Lemon, vinegar, honey, and sugar are all antimicrobial ingredients and can be used to preserve food. Sundrying, storing in wood ash, spraying juice of certain leaves, storing in colder place or under the dry soil etc. are some common practices to preserve food in Nepal. Food is also preserved by freezing, boiling, pasteurization and storing in cold store in cities. Reasonable Fact Plenty of mustard oil is used while making pickles from dried radishes. Plenty of mustard oil is used while making pickles from dried radish because oil blends with other spices, remove moisture, controls bacterial growth, and reduces fungal activities. As a result, food won’t spoil. Activity 2 Cut thin slices of radish and then let them air dry for a few days in the sun. Salt, mustard seeds, pepper, turmeric powder, and heated mustard oil should all be added. It should be kept for a week in the sun on a regular basis, packed in an airtight plastic container. Will the food last for one month? Observe. 2. Chemical food preservatives Different types of chemicals can be used to preserve food in addition to the traditional food preservatives. To preserve foods, a variety of artificial food preservatives are added. These food preservatives guard against contamination, discoloration, and spoilage. Thus, synthetic food preservatives are those chemicals which are added to food or sprayed on food to protect it from spoiling. Bacteria, yeast, and other microbes are eliminated by these food preservatives. Furthermore, it stops oxidation. Thus, the food can remains fresh for a longer period of time. There are both organic and inorganic synthetic food preservatives. Some examples of chemical food preservatives are sodium benzoate sorbate, sulphur dioxide, nitrates and nitrites, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), calcium propionate, sodium metasulphite, etc. Fact File Seeds are dried and stored in a pot. The mouth of the pot is covered with a thick layer of firewood ash to prevent the entry of bacteria, fungus, moths, spores and wheat weevil. Fact File For food manufacturers, chemical food preservatives bring in a lot of benefits for them because those preservatives make food more eye-catching, more attractive and long lasting.
Oasis School Science and Technology - 10 453 Fig: food that contains chemical food preservatives Importance of chemical food preservatives i. They help in preventing or reducing the rate of microbial (fungal, bacterial etc.) spoilage. ii. They decrease the risk of food-borne diseases because they kill microbes. iii. They maintain the texture of food, flavor, color, and freshness. iv. Food can be transported to different parts because it can be kept for a longer period of time. Adverse effect of chemical food preservatives i. Some synthetic food preservatives can cause deadly allergies in some people. ii. They can cause diarrhoea, abdominal pain and low blood pressure in some people. iii. Benzoates can increase the chance of blood cancer. iv. They can increase the chance of cancer. Reasonable Fact Processed and packaged food such as yoghurt, sauce and bread contain chemical food preservatives. Chemical food preservatives are used in processed and packaged foods like yogurt, sauce, and bread to kill bacteria, mold, and other microorganisms that can cause food to spoil. Activity 3 If you have any processed food, try to find out what preservatives they have used. Most of the time they do not mention it. 3. Food preservatives for induced fruits ripening Those chemical substances which are used to ripen fruits in short period of time are called induced ripening agents. For example, calcium carbide, ethylene gas, ethephon, etc. Artificial ripening helps to ripen fruits faster. Traditionally we ripen fruits covering them by thick jute bags, cotton bags, blanket, etc. But, nowadays different types of synthetic chemical substances are used to do it. The most popular chemical ripening agent is calcium carbide.
454 Oasis School Science and Technology - 10 Calcium Carbide Calcium carbide, also known as CaC2 , is a white chemical substance. It can be used to ripen fruits artificially. Acetylene gas is produced when calcium carbide reacts with the moisture in the fruits. Acetylene gas promotes fruit ripening. Artificial ripening helps the ripening of fruits. It develops attractive surface colour in the fruits. It is a cheap and easily available chemical. As a result, most farmers and fruit sellers use it to ripen their fruits. Adverse effects of calcium carbide By keeping the fruit in warm, dark places for several days, local farmers used to ripen the fruits. However, fruit is now ripened using calcium carbide. Health risks could be involved. The following health risks can occur if we consume fruits that have been ripened by calcium carbide. i. A person will experience weakness, vomiting and thirst. ii. It can cause diarrhoea, burning sensation in chest and eye irritation. iii. It can also cause ulcers, sore throat and shortness of breath. iv. It causes heart complications and neurological disorders. v. Fruits ripened through calcium carbide are sweet on surface but sour in core. It's not as tasty as naturally ripened fruit. Reasonable Fact Farmers should not use calcium carbide to artificially ripen fruits. Farmers should not use calcium carbide to artificially ripen fruits because it creates serious health hazards such as heart diseases, neurological disorders and diarrhoea. Activity 4 If you have some unripe bananas, keep them on the top back side of the fridge for 2 days where it is warm. Observe the changes. Antioxidant Oxidation can cause the food to spoil and become discolored. Oxidation is initiated by exposure to sunlight and oxygen. Foods high in fat are generally destroyed by oxidation. If oxidation can be stopped, such foods can be kept for many months. Smoking, salting, fermenting, or adding antioxidants are a few typical methods of preventing oxidation. Tocopherols Fig: fruits that are ripened from calcium carbide Fact File Ethylene and Ethephon are also used in a limited concentration instead of calcium carbide as they are less harmful than calcium carbide. Calcium carbide is already banned in Nepal. Fig: Vitamin C and Figure of vitamin E
Oasis School Science and Technology - 10 455 and ascorbic acid are examples of natural chemicals that can be used to stop food from oxidizing. Antioxidants can also be made from synthetic chemicals like tertiary butylhydroquinone and butylatedhydroxytoluene. The chemical substances that are mixed in the food to prevent oxidations are called antioxidants. Vitamin C, vitamin E, selenium, and beta-carotene are some common antioxidants used to stop food oxidation. The taste and color of the food are preserved by antioxidant. Adverse effects of antioxidants i. Smokers who consume too much beta-carotene have a risk of developing lung cancer. ii. Prostate cancer may develop when vitamin E intake is excessive. iii. Some antioxidants will be harmful as they can interact with some medicines we consume. iv. It may increase the aging process of a body. Reasonable Fact We should not consume food that contains high doses of antioxidants. Foods with high antioxidant concentrations should not be consumed because they can help aging and increase the risk of cancer in our bodies. Activity 5 What natural substances can be used as an antioxidant to preserve food? Find out its answer using Internet. Poisonous chemicals used in homes Acid, chlorine, pesticides, etc. are some poisonous chemicals used in our homes. Acids are corrosive chemicals. They are generally used to clean sinks, toilet bowls, bathroom and kitchen tiles. Chlorine is a chemical that is used to get rid of bacteria and mold from water. Generally, it is kept in water to kill bacteria. In addition, it is used to disinfect sewage. Fig: acid used to clean basin Fig: chlorine to purify water Fig: mosquito repellent Fact File The highest concentration of antioxidants can be found in colorful fruits and vegetables. There is a different antioxidant in each color. Fact File Acid can be mixed with water and poured down into the toilet bowl to kill germs. It should be kept there for a few hours.
456 Oasis School Science and Technology - 10 Reasonable Fact Chlorine is frequently added to the swimming pool. Chlorine is frequently added to swimming pools because it reacts with water to create an acid that can eradicate bacteria, protists, and other microorganisms. Activity 6 Four milligrams of chlorine per litre of water is not harmful to us. Inform your guardians to use the correct amount of chlorine in drinking water tank. Precautions during storage and transportation of poisonous chemicals To get rid of germs and mold, people frequently use insecticides, pesticides, fungicides, rodenticides, bleaching powder, acids, and chlorines in their homes. They should be handled with extreme precaution because they are poisonous and corrosive. They can cause eye and skin burns. Safety measures while storing i. These chemicals must be kept in a ventilated room. ii. They should be stored out of reach of children. iii. To prevent reactions, each type of poisonous chemical should be stored separately. iv. Fire should not be approached to these chemicals. v. Never keep these chemicals close to food, fruits, or vegetables. Safety measures while transporting i. When carrying poisonous chemicals, do not spill anything. ii. Avoid carrying poisonous chemicals in the same vehicle carrying food or clothing. Chemicals Used in Cleaning Our bodies and clothes become dirty as a result of the various jobs and duties. Similarly, the household items like bed sheets, sofa cushions, chairs, tables, curtains, cooking utensils, cups, plates, spoons, etc. also become dirty due to their use. They stick with various dirt, stains, dust, germs, and smell. These foreign substances might also be linked to various diseases. Therefore, it is necessary to remove these foreign materials using various substances known as cleaning agents. 1. Traditional (natural) cleansing agents For cleaning purposes, our ancestors used a variety of natural substances like Reetha, Amla, Shikakai, wooden ash, lemon juice, clay, etc. These are referred to as traditional/ conventional/ natural cleansing agents. a. Reetha, Amla and Shikakai Reetha, Amla, Shikakai, and other ingredients were used to clean hair. This is due to the fact that they are organic and free of poisonous chemicals. They help in dandruff removal, hair strengthening, and hair loss prevention, among other things. Utilizing these substances improves the appearance of hair's health and shining. Fig: reetha
Oasis School Science and Technology - 10 457 b. Wooden ash Traditionally, wooden ash was widely used as a cleansing agent. When wood ash is combined with a small amount of water, it forms a paste. This paste can be used as a mild abrasive to clean stained metals and dirty glasses. It also removes adhesives and sticky residue, stain,dirt, dirt, etc. from the clothes, cups, plates and cooking utensils. Like soap, ash is also a disinfecting alkaline agent. The World Health Organization recommends ash as an alternative when soap is not available. Hand cleaning with ash may be effective in removing viruses, bacteria, fungi, and protozoa. However, chemicals in the ash may cause skin irritation. c. Mustard Peena Mustard peena is obtained during mustard oil extraction. Peena contains various vitamins such as B6, niacin, thiamin, and others. It is used for washing strengthening and softening the hair. Peena can also be used as a compost fertilizer. d. Sajeevan Sajeevan is a multipurpose plant that is grown throughout Nepal. It grows with very little water. As a result, it can be grown in poor, infertile soil. Its anti-microbial, anti-cancer and anti- HIV activity has been well recognized. It can be used to brush teeth. Its leaves can also be used to make compost fertilizer. Oil content in the seed could be 30% to 48% but can vary. It's oil is also widely used to make soap and glycerine. It is also called biodiesel because it can be used to power vehicles. It is also used for lighting. e. Lemon juice Lemon juice is one of the best all-natural cleaners. It contains citric acid and has antibacterial properties. It removes adhesives and sticky residue, stain, dirt, dirt, etc. and makes utensils shiny. It is an effective, affordable and ecofriendly way to clean at the home. Importance of natural cleansing agents 1. They are available in natural substances. 2. They do not cause air, water and soil pollution. 3. They do not cause negative impact on the human health. 4. Most of the natural cleansing substances have pleasant smell. 2. Modern(synthetic) cleansing agents We are all familiar with things like soap, shampoo, detergents, sanitizer, and stain remover. They are synthetic cleaners made by humans. These artificial cleaners are used to get rid of things like stains, bad odors, dirt, and dust. The most popular synthetic cleaning agents are soap and detergents. While detergents are made from petroleum byproducts, soap is made from either plant or animal fat. Soaps decompose naturally, whereas detergents do not. When dissolved in water, soap and detergents have the power to clean surfaces like human skin, textiles, and other solids.
458 Oasis School Science and Technology - 10 a. Soap Soap is a sodium salt of fatty acid which is used as cleansing agent. It is made from plant or animal fat, alkali and salt. The process of making soap is called saponification. Sodium oleate and sodium stearate are some examples of soap. Plant or animal fat is boiled in the container. Alkali such as sodium hydroxide or potassium hydroxide (for soft soap) is added during the preparation of soap. The chemical reaction produces soap and glycerin. Sodium chloride is sprayed in the solution to precipitate soap. This precipitate is then collected. Various medicines, oil, perfume, etc. can be added in it. It cannot work properly with hard water. It produces more scum and less lather in hard water. So, clothes is not well washed. However they do not pollute environment because they are biodegradable. b. Detergent Detergent is a sodium salt of benzene sulphonic acid which is used as cleansing agent. Detergents are made from alkali, alkyl benzenes, etc. They have strong cleaning capacity than soap. It can be used in hard water too. They are called soap less soap because they are not chemically soap but they can clean like a soap. Sodium lauryl sulphate, sodium pyrophosphate and alkyl benzene sulphonate are some examples of detergents. They are non-biodegradable. They are persistent. They stay in water and soil for longer time and deteriorate the environment. Effects of Excessive Use of Detergents Detergents aren't completely biodegradable. Detergents from the laundry make their way from the washing machine to groundwater. This water eventually ends up in the ground and in 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. 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.
Oasis School Science and Technology - 10 459 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 by-products. Chemical Pesticides Nepal is an agricultural country. Growing food crops, cash crops, animal husbandry, poultry and fishery are in practice in Nepal. It is one of the main sources of income for farmers and the country. However, millions of net worth of agricultural production are lost due to pests each year. Farmers are using various locally available or industrially prepared toxic substances to control pests. The toxic substances that are used for destroying organisms that are harmful to our crops or animals are called chemical pesticides. To control the pest, we can use locally available chemicals like wood ash, sulfur, neem plant, tobacco plant, dhungri flower, gandhejhar, banmara plant, etc. However, chemical pesticides are widely available and act quickly against insects, rodents, and fungi, most farmers are attracted using them. Pesticides were first introduced in Nepal in 1952. DDT was used to kill the mosquito that spread malaria. Advantage of pesticides i. It controls population of pest by disturbing reproduction or killing them. ii. It increases agricultural production. iii. It prevents pest from damaging stored food. iv. It can prevent diseases in plants. Types of Pesticides There are various types of pesticides. Some of them are given below. 1. On the basis of degradation and non-degradation Pesticides can be classified into two groups based on how biodegradable they are as persistent and non-persistent. . a. Persistent pesticides The pesticides that are stable and can last in the environment for a very long time are called persistent pesticides. They are non-biodegradable. They are not decomposed by microbes. They pollute the air, water and land. They are mostly highly toxic. They are bad pesticides. They are insoluble in water. Persistent pesticides destroy the ecosystem. Dichlorodiphenyltrichloroethane(DDT) and Benzene hexachloride(BHC) are some examples of persistent pesticides. Fact File Farmers use around 396 gram of pesticide per hectare in Nepal nowadays.
460 Oasis School Science and Technology - 10 b. Non-persistent pesticides The pesticides that are degradable and last for a short duration are called non-persistent pesticides. Air, water, sunlight, moisture and microbes can decompose them over time. They do not pollute the environment. They are biodegradable pesticides. These are less toxic to humans. Examples, malathion, dimethoate, jhol-mol, etc. 2. On the basis of target organisms Pests are harmful creatures that harm our crops, furniture, pets and domestic animals. Pesticides can also be classified based on the pest they kill. a. Insecticides Insects such as flea beetle, cabbage looper and corn ear-worm, etc. destroy crops. The chemical compounds that are used to control or kill insects are called insecticides. Nitenpyram, fenvalerate, malathion, etc. are commonly used insecticides in Nepal. b. Fungicides Fungi damage our crops each year. They mostly cause disease in our vegetables. The chemical compounds that are used to control or kill fungi are called fungicides. Dimethomorph, mancozeb, sectin and carbendazim are common fungicides. c. Herbicides Weeds growing in fields can steal minerals and fertilizer. It should be removed or killed. The chemical compounds that are used to control or kill the herbs are called herbicides. Butachlor, isoproturon, atrazine etc. are some common herbicides. d. Rodenticides Rats, mice, squirrels and porcupine destroys crops. They can be killed or chased. The chemical compounds that are used to control or kill rodents are called rodenticides. Rodenticides are very toxic. It can be poisonous to other animals too if they eat poisoned rats. Bromadiolone, coumatetralyl, zinc phosphide, etc. are some common rodenticides. e. Miticides Mites are harmful insects. They are harmful to humans. They are especially parasites to bees. The chemical compounds that are used to control or kill mites are called miticides. Fenazaquin, propargite, etc. are common miticides. 3. Based on the nature of the action On the basis of nature of action, there are following types of pesticides. a. Contact pesticides Some chemicals can kill pests or herbs when they come in physical contact. Such chemical compounds are called contact pesticides. Malathion, chlorpyrifos, etc. are some common contact pesticides. b. Stomach pesticides Some pesticides are usually mixed with crops or foods and left so that rodents or insects will eat them and die. Such chemical insecticides that can control or kill pests when they are eaten are called stomach pesticides. Malathion, cypermethrin etc are some stomach pesticides.
Oasis School Science and Technology - 10 461 c. Systemic pesticides Some pesticides are absorbed by leaf or roots of plants or the skin of animals and distributed all over the body internally. Such chemical compounds are called systemic pesticides. It makes a part or entire body of a plant toxic so that any herbivore pest such as aphids, nematodes and caterpillars that feed on them, dies later. Multineem, biomultineem, neonicotinoid,etc. are common systemic pesticides. d. Fumigants pesticides Fumigants are chemical compounds that convert into toxic fumes when it comes in contact with moist air. It can be liquid, pellet or powder. It is usually mixed with stored grains. Aluminium phosphide and methyl bromide are common fumigant pesticides. Effect of Chemical Pesticides Chemical pesticides harm our health both immediately and over time. It can lead to eye irritation, blisters, rashes, nausea, vomiting, cancer, blindness, and even death. Additionally, it harms the ecosystem, water, and soil. These agricultural chemicals are extremely toxic. Farmers must become familiar with safety precautions for handling, storing, and using these chemicals. Precaution while purchasing pesticides i. We should purchase only those pesticides that are allowed by Nepal government as described in Pesticide rules, 2050 B.S.. ii. We should consult with agriculture officer and get approval before buying highly toxic pesticides. Precautions while storing pesticides i. Observe the storage guidelines provided by the manufacturer. Never take the label off. ii. Maintain pesticides in their original packaging. Never pour into additional containers. iii. Keep pesticides far away from the sources of fire. iv. Keep it out of reach of children and animals. v. It should be kept in a dark, well-ventilated area that is locked. vi. We should never keep food close by in storage. Precaution while transporting pesticides i. Food products and pesticides should be transported separately. ii. No passengers should be allowed in a cabin with pesticides. iii. While transporting it, proper safety equipment should be worn. iv. While transporting it, we should avoid spilling and leaking. Reasonable Fact Pesticides should be handled with caution. Pesticides should be handled carefully because they are toxic and can lead to cancer, blindness, neurological disorders, diarrhoea, and poisoning. Fact File According to a report co-authored by the Food and Agriculture Organization, weeds, pests, and diseases rob the world's potential crop production of about one-third of its output each year.
462 Oasis School Science and Technology - 10 Activity 7 If there is a container of pesticide, read the label and directions to store, transport and use it. Wear gloves and a mask before holding it. Precaution While Using Pesticides i. Farmers need to be trained for using pesticides. ii. Safety equipment like gloves, apron, boots, gas masks, etc. should be used while using pesticides. iii. Eating and drinking should be avoided while using pesticides. iv. Farmers should use the minimum of pesticides. v. Chemical kits should be used by farmers to minimize spills and splashes when applying pesticides. vi. Farmers need to take precautions to prevent the exposure of children, non-target animals, insects, and birds. vii. Farmers should use good pesticides that are biodegradable and less toxic to humans. viii. Farmers should practice Integrated Pest Management where all available pest control techniques are used to control the population of pest. Environmental impact of dichloro diphenyl trichloroethane(DDT) i. DDT is a very fine powdered insecticide. So, it causes air, water and soil pollution. ii. Covering of bird's egg (the shell) becomes thin and weak. 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. Chemical Pollution When different types of natural and human generated chemical substances are mixed in air water and soil, they degrade their quality. Human activities are mainly responsible for this. The everyday human activities such as the use of chemical fertilizers, insecticides, pesticides, soaps, detergents, dyes, synthetic fibres, plastics, industrial waste products, etc. lose original quality of the environment. The pollution which is caused by mixing unwanted or excessive use of chemical substances in soil, air and water is called chemical pollution. Causes of chemical pollution There are various natural and human generated factors which are responsible for chemical pollution. Some of the factors that cause chemical pollution and their respective harmful impacts are explained below: 1. Chemical fertilizers, insecticides and pesticides used by farmers in the fields To meet the requirement of ever growing population, agricultural science is also advancing. Farmers use more and more chemical fertilizers to produce more quantity of crops. These chemical fertilizers increase acidity and decreases the quality of the land as well as air and
Oasis School Science and Technology - 10 463 water. Not only fertilizers, farmers use more quantity of insecticides and pesticides to kill or control harmful insects and pests. These poisonous chemicals also degrade the quality of air, water and soil. Insecticides kill useful microbes, insects, mammals and birds too. It disturbs ecosystem. Chemical fertilizers and pesticides are washed away by rain into the river. It kills aquatic life, causes infertility, kills eggs, etc. 2. Unmanaged household wastes and plastics Different types of solid wastes of food, vegetables, clothes, ceramics, soaps, detergents, plastics, glass, etc. are also great sources of chemical pollution. Among these wastes, some are bio-degradable and some are non-biodegradable. The non-biodegradable wastes cause permanent pollution in soil, air and water. So, these two categories of pollutants should be managed separately. Reasonable Fact Plastic pollution is considered as one of the major chemical pollution. Plastic is non-biodegradable and remains on the site of disposal for long period without decomposition. In land, it causes land pollution by reducing fertility by covering the surface of land, distorting the texture of soil, limiting infiltration of water to ground and disturbing run-off. In water bodies, it blocks light, water - oxygen interaction and threatens aquatic ecosystem. When burnt, it releases toxic gases like dioxins, furans, PCBs into the air and poses a threat to vegetation, and human and animal health. So, it is considered as one of the major chemical pollution. 3. Toxic gases, smoke, dust, and other particles emitted from the industries Different types of harmful gases like carbon dioxide, sulphur dioxide, carbon monoxide, oxides of nitrogen, etc. are the main air pollutants, which are emitted from the industries and factories. These gases are responsible for green house effect, ozone layer depletion and acid rain formation. Various types of dust particles emitted from vehicles, industries and factories directly enter into the respiratory organs causing different types of respiratory diseases. These particles also deposit over the surface of leaves blocking transpiration, evaporation and photosynthesis. 4. Different types of food colours To attract customers and users, food manufacturers and traders use different types of colours in the food stuff. Colours are man-made chemical substances, which directly or indirectly affect the health of people. 5. Mixing of different types of metallic particles From different types of automobiles, industries, factories and research centres, several types of metallic particles, such as lead, chromium, mercury, arsenic, etc. are released. These metallic particles when mixed with air, water and soil degrade their quality. 6. Mixing of different types of dyes and detergents Different types of industries like leather, textiles, carpet, etc. also release harmful colours, dyes and detergent. These chemical substances when mixed with air, water and soil lose their quality. 7. Warfare Different types of minor and major warfare use nuclear weapons, bombs and other chemicals. These substances cause air, water and soil pollution.
464 Oasis School Science and Technology - 10 Control of Chemical Pollution We can control chemical pollution in the following ways : i. Farmers must be given training to use chemical fertilizers, insecticides, pesticides in proper ways. ii. Industries, factories, research centres, etc. must be established far from city areas. iii. Farmers are suggested to use organic fertilizers and bio-insecticides. iv. Waste water and liquid coming from industries and factories must be purified before throwing them into water sources and fields. v. Toxic gases should not be allowed to mix in the air. vi. Chimneys must be used in industries and factories. vii. Solid wastes such as plastic, clothes, glasses, carpets, ceramics, etc. should be managed properly. viii. The use of nuclear weapons, bombs and chemicals must be stopped. ix. Population growth must be controlled. x. Unorganized urbanization should be changed into organized urbanization. xi. Sustainable development must be made. xii. The most important measure is to create awareness among the people about the effects of chemical pollution. xiii. 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. Reasonable Thinking Skill Reasonable Thinking Skill R T S 1. Hydrochloric acid is widely used as a cleaning agent. Hydrochloric acid is widely used as a cleaning agent because it is corrosive. Since it is corrosive, it can be used to remove stains and rust. It can also kill germs. 2. Pesticides are poisonous chemicals. They are lethal. How should we store it in the house if there are little kids in the house? Pesticides are lethal. They can kill people. If we have little kids in the house, we should be extra careful about storing them. i. We should not keep it in other containers but in the original one. ii. The containers must be closed properly. iii. It should be stored far away from the reach of children, animals or teens. iv. Children should never be allowed to touch it. v. It should be stored where flood water cannot reach it. 3. Lemon is cut and dipped in dishwashing water. It makes the dish cleaner than normal water. The lemon is cut and dipped in dishwashing water so that the dish can be cleaner. The reason for this is the presence of a higher concentration of citric acid. The lemon naturally contains a higher concentration of citric acid. So, it can remove stains, oil, rust and kill germs.
Oasis School Science and Technology - 10 465 4. Detergent, colin, nail polish remover etc. are synthetic cleaning agents. They are harmful to the environment. As a good citizens, what should we use instead of synthetic cleaners? Detergents, colin etc. are synthetic cleaners that are very harmful to the environment. As good citizens, we can use traditional, biodegradable cleaning agents. i. We can use amla, reetha etc. to clean our hair. ii. Wooden ash can be used instead of detergent. iii. Lemon juice can be used to clean dishes, basins and clothes. 5. Farmers use calcium carbide to ripen fruits. Should they use it? What should they do instead of ripening the fruits? Some farmers use calcium carbide to ripen fruits. They should not use it because it can cause cancer. Instead, they should let the fruit ripen naturally. Or they can collect fruits, cover them and store them in a warm place for a few weeks. 6. DDT destroys the ecosystem. DDT is a very deadly poison. It is non-biodegradable. It kills any life that comes into its contact. Hence it causes an imbalance in the ecosystem. Ecosystem will be destroyed. 7. 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. 8. Pickled spinach last for many days. Pickled spinach lasts for many days because its acidic environment reduces microbial activity. 9. 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? 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 pH value of the soil and use a required chemical to balance pH value of soil. 10. The 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. Degradable waste should be used for composting. ii. Metals, plastic and glasses should be recycled. iii. Non-degradable waste that cannot be recycled should be burnt in the incineration.
466 Oasis School Science and Technology - 10 Exercises 1. Choose the best answer from the given alternatives. a. What is mostly responsible for food spoilage? i. bacteria ii. salt iii. sugar iv. air b. Why preservative should not be added to canned food? i. germs do not spoil food in metallic cans ii. canned food does not contain germs because food is boiled iii. food automatically produces preservatives when canned iv. the air in the can is toxic and kills bacteria c. How does salt preserve food? i. it is toxic to bacteria. ii. it absorbs water from bacteria and food and decreases microbial activity iii. it stops oxidation iv. it produces antioxidants d. Why is dilute acid used to clean toilet bowls? i. acid can kill germs and remove stains ii. acid can remove bad smells iii. acid is detergent iv. acid is a liquid soap 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 preservatives b. Traditional food preservatives c. Canned food d. Synthetic food preservatives e. Antioxidant f. Pesticides g. Chemical pollution 3. Answer the following questions in very short. a. Write the name of locally available substances used to preserve food? b. What do synthetic food preservatives do? c. Which industrial chemical compound is used by farmers to ripen bananas? d. How is wood ash used as a cleaning agent?
Oasis School Science and Technology - 10 467 e. What are soap and detergent usually made of? f. What property makes lemon juice suitable as a cleaning agent? g. What is a sodium salt of fatty acid called? h. What is the full form of DDT and BHC? 4. Give reasons. a. Food preservatives can prevent spoilage. b. Canned food lasts very long. c. Traditionally meat is smoked and salted. d. Synthetic food preservatives are effective to preserve food. e. Antioxidant is used to preserve food. f. We should not consume excessive food which contains antioxidants. g. Calcium carbide is used to ripen fruits but we should avoid such fruits. h. Insecticides should be kept out of reach of children. i. If possible, farmers should not use chemical pesticides and use bioinsecticides. j. Farmers should use gloves and masks while using agrichemicals. k. Acid is a good cleaning agent for toilet bowls and tiles. l. Detergent is called soapless soap. m. DDT is banned in Nepal. n. Sajeevan is called biodiesel. 5. Differentiate between the following. a. Traditional food preservatives and synthetic food preservatives b. Food preservatives and antioxidants c. Soap and detergent d. Chemical insecticides and bioinsecticides e. Biodegradable pesticide and non-biodegradable pesticide f. Fumigant pesticide and stomach pesticide 6. Answer the following questions in short. a. What is the objective of adding food preservatives to food? Write its importance. b. How is meat usually preserved traditionally? c. What are the advantages of poisonous agrichemicals? d. How should agrichemicals be handled? e. What are the precautions while transporting and storing poisonous chemicals? f. Write a short note on modern cleansing agents. g. What are the harmful effects of excessive use of detergents? h. What are the uses of detergent? i. How do detergents harm the environment and human health?
468 Oasis School Science and Technology - 10 7. Answer the following questions on the basis of the given figure. i. What is it in the diagram? ii. What is its primary objective? iii. What is the reason that food won’t go bad in it? 8. Answer the following questions. a. How is radish pickled? Explain. b. What are the positive and negative effects of using synthetic food preservatives? c. What are the advantages of antioxidants? Mention its adverse effects. d. What is the use of calcium carbide? How do farmers ripen fruits artificially? Describe procedure. Why it should not be used? e. What are traditional cleaning agents? Enlist them. How are they used? f. Discuss the importance of natural cleaning agents. g. What are the materials used in your house and surrounding as a cleaning agent? Make list. Mention its impacts on the environment. h. What is chemical pollution? What are its causes? Describe. i. What are the precautions while using chemical pesticides? j. What are the raw materials required to make soap? How is soap produced? Describe in brief. k. Write a short note on usefulness of sajeevan plant, reetha, wooden ash and pina. l. Enlist the pesticide based on target organism. Describe each of them. m. What are different types of insecticides based on nature of action? Enlist and describe each of them.