Detailed explanations in West Bengal Board Class 7 Science Book Solutions Chapter 4 Role of Substances in Environment offer valuable context and analysis.
WBBSE Class 7 Science Chapter 4 Question Answer – Role of Substances in Environment
(Page no. 101)
Write the names of two metallic and four non-metallic elements in the blank space.
Answer:
Metallic elements Iron, Copper.
Non ntetallic elements Graphite, Hydrogen, Sulpher, Phosphorus.
Write the names of three non-metals that are more abundant in human body than in earth curst.
Answer:
(1) Oxygen, (2) Carbon, (3) Nitrogen
We can see from the table that about 97% of the total mass of human hody can be attributed to the combined mass of four elements. Can you identify them?
Answer:
- Oxygen
- Carbon
- Nirtrogen
- Hydrogen.
(Page no. 105)
mention the different parts of plants that we take as food.
Answer:
| Parts of a plant body | Name of the plant |
| Underground root | Beat root, carrot, radish |
| Underground or normal stem | Potato, sweet potato. |
| Flower | Cauliflower, Pumkin flower. |
| Fruit | Mango, Apple |
We take different fruits of different plants. Do they have the same taste? Share your previous experience with your friends and complete the following table :
Answer:
| Name of familiar fruits | Their taste |
| Lemon | Sour |
| Ripe Mango | Sweet |
| Pine Apple | Sweet |
| Orange | Sour and Sweet |
| Apple | Sweet |
With the help of your teacher prepare a sugar solution, salt solution and vinegar solution.Try to recognise them by taking their taste.
Answer:
| Taste of the sample solution | Sample seems to be |
| Sweet | Sugar solution |
| Salty | Salt solution |
| Sour | Vinegar solution |
(Page no. 107)
We use acids for various purposes. Do you know any such use of acid? Discuss among yourselves and write.
Answer:
| Which substance | Used in which field |
| Juice of lemon (citric acid) | To turn milk into posset. |
| Muriatic acid | To clean toilets. |
| Vinegar | To store fish and meat. |
Now notice whether any change occurs or not :
Answer:
Prepare a solution of baking soda with drinking water in a glass with the help of your teacher.
Now taste this solution along with previously prepared vinegar solution (or filtered lemon juice) and a little of lime water. Note down your observation.
Answer:
| Which solution | How does it taste |
| Vinegar solution | Sour |
| Baking soda solution | Bitter and soapy feel. |
| Lime water | Bitter and soapy feel. |
(Page no. 108)
If you know about any other uses of lime or any other base then write down after discussion with your friends.
Answer:
| Name of the substance | Its use |
| Sodium Hydroxide | Manufacture of soap |
| Magnesium Hydroxide | As an antacid. [neutralizes acidity] |
(Page no. 109)
Take hibiscus petal juice into seperate glasses. Add vinegar in one glass and lime water in another glass. Note down the observations.
Answer:
Vinegar is an acid. It changes the colour of hibiscus petal juice from pink to green. Again lime water is a basic substance. It changes the colour of hibiscus petal juice from pink to red. Here Hibiscus petal juice serves as an indicator.
(Page no. 111)
Take some indicators like litmus, phenolphthalein or methyl orange. Note the change in their colourwhen they are added to various solutions, Write down your observation in the following table :
Answer:
If you know about any example of such type of neutralization reaction in your daily life around your house, share it among yourselves and write it down.
Answer:
(Page no. 114)
Test the following solutions with a pH paper and see whether they have a pH equal to greater than or less than 7.
Answer:
(Page no. 117)
You need a few pieces red and blue litmus papers and some samples to identity. Then like the previous experiments, test the samples with red and blue litmus papers and fill up the following table :
Answer:
(Page no. 118)
For proper functioning of our body, the right balance of acidity and basicity must be maintained. Different fluids of our body have different extents of acidic and basic nature (pH). Can you tell anything about the nature of those fluids mentioned below?
Answer:
(Page no. 120)
Carefully observe the two pictures of the two principal sources of our food.
1. Plant source and 2. Animal source
Make a small chart about the food you generally take from these two origins.
Answer:
In how many ways we eat these foods?
Answer:
1. raw
2. roasted
3. boiled
4. eat after cooking.
(Page no. 122)
Almost 47 compounds have been reported to be present with the sea salt among which 7 compounds are important. These are –
Answer:
(Page no. 129)
How can salt be used in following cases ?
Answer:
| Problem | Use of common salt |
| In your toothache | You must rub gum with salt |
| One day when you suffered suddenly from vomiting and diarrhoea | You must take a small amount of solution made from a little salt and sugar at rugular intervals |
| In your throat pain | You must gargfe with mild hot water mixed with salt |
| A leech bites in your leg | You must use salt on the biting spot to stop bleeding |
| Preservation of ripe tamarind | You must add salt with tamarind |
| If a symptom like low blood prseeure is found in someone | He must take salty food to increase blood pressure |
(Page no. 129)
Discuss with your friends and prepare a list of the things you use from morning to night. Mention whether these materials some from natural, synthetic or manmade sources.
Answer:
(Page no. 131)
Sometimes sit-and-draw competitions are held in your locality or in your school. The equipments required for this purpose are shown below. Write their names and then write after discussion whether they are natural, processed or synthetics.
Answer:
(Page no. 132)
What other things can be made from these synthetic materials.
Answer:
| Name of the synthetic material | Its use cups, boxes, bottles, containers, helmets, electronic goods |
| Plastic | pipes, rain coat, shoes, automobile and health care goods |
| PVC | water pipe and tank, bottles, drums, iceboxes, toys, ropes |
| Polyethylene | fancy bags, seatcover, shoes, cushions etc. |
| Rexin | Its use cups, boxes, bottles, containers, helmets, electronic goods |
(Page no. 135)
Write the names of the synthetic materials used as a body soap, washing soap or for other activities mentioned below.
Answer:
| Use | Materials |
| Bathing and washing | bathing soap |
| Clesning hair | shampoo |
| Washing and cleaning utensils | bar soap or liquid soap |
(Page no. 137)
The picture of some of your familiar things below. Can you identify them. Write their uses.
Answer:
| Name of the substance | Uses |
| a. Vaseline | mosturises body, heal minor skin scratches and burns |
| b. Shampoo | used to clesnse hair |
| c. Lipstick | used by women to cslour lips |
| d. Toothpaste | used to clean and maintain nealth of the teeth |
| e. Body spray | They make you smell ‘extra nice’. |
| f. Powder | makes skin smooth, used to set makeup |
| g. Nail polish | to colour nails |
| h. Tips | used by women for beautification of face |
(Page no. 137)
Make a list of colourful objects, both organic and inorganic, around you and try to know about the source of their colours with the help of your teacher.
Answer:
| Objects | Source of colour |
| Carrot | Organic |
| Turmeric | Organic |
| Petals of rose or marigold | Organic |
| Coloured plastic tumbler | Inorganic |
Class 7 Science Chapter 4 Question Answer West Bengal Board – Role of Substances in Environment
Multiple Choice Questions & Answers : (1 mark for each question)
Question 1.
The most abundant element found in human body is–
i) Aluminium
ii) Silicon
iii) Oxygen
iv) Carbon
Answer:
iii) Oxygen
Question 2.
The water content in human body is near about–
i) 60 %
ii) 70 %
iii) 90 %
iv) 80 %
Answer:
i) 60 %
Question 3.
If there is increased quantity of fat in a body then water content is-
i) less
ii) exceeds
iii) remain the same
Answer:
i) less
Question 4.
Next to oxygen, the most important requirement for our survival is
i) air
ii) light
iii) water
Answer:
iii) water
Question 5.
Iron is an essential component of-
i) bones
ii) red blood cells
iii) nerve
iv) skin
Answer:
ii) red blood cells
Question 6.
The major constituent of bone is a phosphate of-
i) iron
ii) sodium
iii) magnesium
iv) calcium
Answer:
iv) calcium
Question 7.
Energy required for germination of the seed comes from-
i) protein
ii) water
iii) carbohydratrates
Answer:
iii) carbohydrates
Question 8.
Breakdown of lipids in a cell gives-
i) strength
ii) energy
iii) stimulation
Answer:
ii) energy
Question 9.
The fluid secreted from the body of an ant is-
i) acid
ii) base
iii) salt
Answer:
i) acid
Question 10.
Water in nature is-
i) acidic
ii) basic
iii) neutral
Answer:
iii) neutral
Question 11.
When acids are dissolved in water, they release-
i) oxygen ions
ii) hydrogen ions
iii) nitrogen ions
Answer:
ii) hydrogen ions.
Question 12.
The ion which is present in common salt is-
i) Sodium
ii) Potassium
ii) Berium
Answer:
i) Sodium
Question 13.
Iodine deficiency cause-
i) high blood pressure
ii) low blood pressure
iii) goitre
iv) heart disease
Answer:
iii) goitre
Question 14.
A polymer called polythene is prepared by joining molecules of-
i) Methane
ii) Chlorine
iii) Ethylene (C2 H4)
Answer:
iii) Ethylene (C2 H4).
Question 15.
The acid present in tamarind-
i) malic acid
ii) lactic acid
iii) acetic acid
iv) tartaric acid
Answer:
iv) tartaric acid
Question 16.
In general taste of alkali is-
i) acidic
ii) bitter
iii) basic
iv) tasteless
Answer:
ii) bitter
Question 17.
A crystaline subject-
i) chalk
ii) lime
iii) sand
iv) sugar
Answer:
iv) sugar
Question 18.
If the pressure of blood increases what may happen in our body-
i) veins can rupture
ii) heart valves may be damaged
iii) blood clots may be formed in the brain
iv) all are true
Answer:
iv) all are true
Fill in the blanks : (1 mark for each question)
1. Most of the things of the earth are made from a reserve of about ________ elements.
Answer:
92.
2. Human body is mainiy formed of the combined mass of __________ elements.
Answer:
four.
3. We get _______ from inorganic compounds.
Answer:
minerals.
4. Using the energy of _____, plants produce glucose.
Answer:
Sunlight.
5. – is an important constituent of the body of organisms.
Answer:
Water.
6. Water constitutes about _____ of the total mass of human body.
Ans:
60 %.
7. An increased quantity of _____ correlates with a decreased _____ content.
Answer:
fat, water.
8. Next to oxygen, ______ is the most important requirement for our survival.
Answer:
water.
9. The major constituent of bone is a phosphate of ______.
Answer:
calcium.
10. Without ferrous ion (Fe2+) ________ of blood’s red blood cell cannot function.
Answer:
haemoglobin.
11. Energy required for germination of the seed comes from ______ stored in it.
Answer:
carbohydrates.
12. The protein called haemoglobin transports _______ to different parts of our body.
Answer:
oxygen
13. Bases soluble in water are known as _______
Answer:
alkalis
14. All _______ are bases but all bases are not alkalis.
Answer:
alkalis
15. Lemon juice causes stain on _______ floor.
Answer:
cement
16. The concentrated alkali solution is extremely harmful for skin and _______.
Answer:
eyes
17. _______ is mixed with pond water to decrease its ______ during culture of fish in pond.
Answer:
Lime, acidity.
18. Our body also contains acid in the ______.
Answer:
stomach.
19. ______ of Calcium in our body is in our bones.
Answer:
99 %.
20. _______ is necessary for deposition of Calcium in the bones.
Answer:
Vitamin D.
21. One important constituent of our blood is _______.
Answer:
White Blood Corpuscles (WBC).
22. To meet the demand of salt in reserve forests there are ______ for animals.
Answer:
salt licks.
23. ______ helps in maturation of brain, so it is essential for children.
Answer:
lodine.
24. Generally iodine deficiency problems are more in _______ regions than in plains.
Answer:
hilly.
25. The fibres in the plant body are made of different types of _______ polymers.
Answer:
carbohydrate.
26. The muscles, tendons, ligaments etc of animal bodies are made up of _______, which also are polymers.
Answer:
Proteins.
27. _______ is the sodium or potassium salt of some organic acids which are prepared from the reaction of coustic soda or caustic potash with _______ or oils.
Answer:
Soap, fat.
28. The ______ used for writing or printing is mixture of pigments.
Answer:
ink.
29. _______ is a mixture of oxides and Silicate compounds of many metals like Calcium, Aluminium, Iron etc.
Answer:
Cement.
30. Some of the widely consumed soft drinks in our country are found to contain ______ in alarming quantities.
Answer:
pesticides
State whether True or False : (1 mark for each question)
1. Carbonic acid is present in vinigar.
Answer:
false
2. Apple contains malic acid.
Answer:
true
3. Lactic acid is present in curd.
Answer:
true
4. Our body contais acid in the stomach.
Answer:
true
5. Alkali turns moict red litmus white.
Answer:
false
6. The taste of blood is sour.
Answer:
false
7. Water does not change the colour of litmus paper.
Answer:
true
8. If our kidneys get affected due to some reason, then urea, uric acid and creatinine levels in the blood decrease.
Answer:
false
9. Common salt is a white, crystalline mixture.
Answer:
true
10. Some salt enters our body through the water we drink.
Answer:
true
11. Pure sodium chloride absorbs water from air.
Answer:
false
12. The main constituent of human blood is water.
Answer:
true
13. Milk, curd, bones of small fishes sre the main sources of iron.
Answer:
false
14. Cactas, Acacia, Palm grow in hot and dry areas.
Answer:
true
15. Iodine helps in maturation of brain.
Answer:
true
16. Many small molecules join together to form a molecule of a polymer.
Answer:
true
Match the column A with column B.
| Column A | Column B |
| a) PET is used for | i) are present in tomato |
| b) Many countries has banned | ii) grow in mangrove forest |
| c) The substances decomposed through | iii) preparing bottle and food boxes |
| d) Malic, oxalic and sitric acids | iv) high temperature |
| c) Carbonic acid is present | v) haemoglobin cannot be formed |
| f) Animals that hunt at night | vi) DDT as pesticide |
| g) Cactus can tolerate | vii) natural process are known biodegradables |
| h) Without ferrous ion | viii) red litmus blue |
| i) Sundari trees | ix) can see in the dark |
| j) Alkali turns | x) in sodawater |
Answer:
a) PET is used for preparing bottle and food boxes.
b) Many countries has banned DDT as pesticide.
c) The substances decomposed through natural process are known biodegradables.
d) Malic, oxalic and citric acids are present in tomato.
e) Carbonic acid is present in sodawater.
f) Animals that hunt at night can see in the dark.
g) Cactus can tolerate high temperature.
h) Without ferrous ion haemoglobin cannot be formed.
i) Sundari trees grow in mangrove forest.
j) Alkali turns red litmus blue.
Very Short Questions & Answers : (1 mark for each question)
Question 1.
What are the main constituents of common salt?
Answer:
Sodium Chloride, Magnesium Chloride, Calcium Sulphate and Potassium Bromide.
Question 2.
What is the symbol of Sodium Chloride?
Answer:
NaCl arrow Sodium ion (Na+) + Chloride ion (Cl-).
Question 3.
What are the two functions of Calcium?
Answer:
a) Helps in formation of bones and teeth. b) Controls the function of heart muscle.
Question 4.
What are four elements prevalent in human, bacterial, fungal, plant and animal bodies?
Answer:
Carbon (C). Hydrogen (H), Oxygen (O) and Nitrogen (N).
Question 5.
How plant produce glucose?
Answer:
Utilising carbon dioxide from air, taking up water and some minerals from soil and using the energy of sunlight, plants produce glucose.
Question 6.
How the harmful compounds of our body are excreted?
Answer:
It occurs through sweat and urine most of which is water.
Question 7.
What are the two different components of paints?
Answer:
i) Solvent part (generally colourless or light-coloured liquids)
ii) pigment part (particles of coloured compounds)
Question 8.
What is the reason for wide use of cement?
Answer:
This is because cement is easily available, can adapt itself with weather and structures made of cement have a high longevity.
Question 9.
What will happen of you prepare ball of cement, sand and water and keep it overnight?
Answer:
The entire ball will get hardened.
Question 10.
Write the name of theree non-metallic element.
Answer:
i) Oxygen ii) Carbon iii) Hydrogen
Question 11.
What link a fuel to our body?
Answer:
Regarding production of energy in the body of an organism, carbohydrates may be likened to a fuel.
Question 12.
What is protein?
Answer:
Protein is a class of compound without which life cannot be imagined.
Question 13.
Where protein is found in our body?
Answer:
Proteins are found in skin, muscle, nail, hair and blood.
Question 14.
What speed up numerous chemical reactions that occur in our body?
Answer:
Various enzymes.
Question 15.
On what the external appearance of the progeny of an organism depends. is
Answer:
The external appearence of the progeny of an organism depends on their nuclic acid.
Question 16.
What partly determines the behavioural pattern of an animal?
Answer:
The behavioural pattern of an animal is determined partly by its genetic make up.
Question 17.
Name the four metals that are essential for our survival.
Answer:
These metals are Sodium, Potassium, Catcium and Iron.
Question 18.
When you eat fried fish, you ingest very small pieces of bone along with the fish, what it contains?
Answer:
It contains a phosphate compound of Calcium.
Question 19.
What is there in the Calcium tablets prescribed by doctor?
Answer:
It contain Calcium Carbonate (CaCO3), along with some organic substances.
Question 20.
What is there in anima! liver?
Answer:
It contains specific organic compounds of iron.
Question 21.
What is required for the proper functioning of nervous system?
Answer:
It requires the right balance of Sodium and Potassium ions (Na+.and .K+)in our body.
Question 22.
Name four organic compounds which play a vital role when life first came into being?
Answer:
i) (‘arbohydratc. ii) Protein, iii) lipid, iv) nucleic acid.
Question 23.
With what tie iatu exiernal shell of snails, conches and the like is made of?
Answer:
Calcium Carbonate.
Question 24.
How many elements are present in living organisms in form of various compounds?
Answer:
16 elements.
Question 25.
How is lipid important?
Answer:
Breakdown of lipids in a cell given energy. Moreover the layer of lipid below the skin of an animal protects it from cold.
Question 26.
Name some substances other than fruit which tastes sour?
Answer:
Sour milk, vinegar, curd.
Question 27.
What is acid?
Answer:
An acid is a substance which produces hydrogen ions (H–)when dissolved in water.
Question 28.
From where the word acid come from?
Answer:
The word acid came from the Latin word Acidus, which means ‘sour’.
Question 29.
Name an acid which produced in our stomach, how is it useful?
Answer:
Hydrochlcric acid, it helps in the digestion process.
Question 30.
What we take to reduce acidity in stomach?
Answer:
An antacid, which is a base, is taken.
Question 31.
What is neutralisation reaction?
Answer:
The reaction of an acid with a base to form salt and water is called neutralisation reaction.
Question 32.
Which acid is present in ant bite?
Answer:
Formic acid ( HCOOH).
Question 33.
What is base?
Answer:
A base is a ompound that produces hydroxyl ions when dissolved in water.
Question 34.
What is alkali?
Answer:
A base that is soluble in water is called an alkali.
Question 35.
Write the dissociation reaction of HCl in aqueous solution?
Answer:
HCl + H2O → H3 – + Cl
Question 36.
How can you write the dissociation of slaked lime in lime water?
Answer:
Ca(OH)2 arrow Ca+2 + 2 OH–
Question 37.
What is p H scale?
Answer:
The strength of acidity or basicity of a solution is measured by pH scale.
Question 38.
How much of our daily food should be acidic and basic?
Answer:
Our daily food should be 20% acidic and 80% basic.
Question 39.
Name the foods which are basic in nature.
Answer:
Foods coming from plant origin are mainly basic in nature e.g. fruits, nuts, legumes and vegetables.
Question 40.
Name the foods which are acidic in nature.
Answer:
Foods coming from animal origin like fish, meat,egg are acidic.
Question 41.
How many types of salt do we use now a days as food?
Answer:
They are mainly of three types –
(i) Sea salt
(ii) Rock salt
(iii) Table satt.
Question 42.
What is the medium of communication in our body?
Answer:
It is our nervous system, which is continuous from our nails of feet to head.
Question 43.
What assists the nerve in the activity of communication?
Answer:
To exchange impulse between brain, spine and different parts of the body the main helper of nerve is the sodium ion (Na+)present in the colımon salt.
Question 44.
What will happen if the level of salt in our body suddenly decreases due to some reason?
Answer:
For this sparm will occur in different parts of the body, talking will become inconsistent.
Question 45.
Where from the word ‘polymer’ is derived?
Answer:
The word ‘polymer’ is derived from two Greek words ‘poly’ and ‘meros’. ‘Poly’ means many and ‘meros’ means parts.
Question 46.
Name some fertilisers.
Answer:
Urea, Ammonium Sulphate, Ammonium Phosphate.
Question 47.
Name some pesticides.
Answer:
Methyl parathion, Aldrin, Carboryl.
Question 48.
What are the adverse effects of Lead and Mercury?
Answer:
Lead causes – loss of appetite. nausea, headache.
Mercury causes – Loss of sense in facial and tongue muscles, kidney damage.
Question 49.
What has been found in some of the widely consumed soft drinks in our country?
Answer:
Some of the widely consumed soft drinks in our country contains pesticides in alarming quantities.
Question 50.
What herbal medicine was used earlier for small cuts or bruises?
Answer:
Extract of marigold plant or grass .
Question 51.
In early days what was used for dying of clothes?
Answer:
Indigo.
Question 52.
Whose body contains more water male or female?
Answer:
male
Question 53.
Whose body contains more water child or adult?
Answer:
child.
Question 54.
Whose body contains more water a thin person or a fat man?
Answer:
thin person.
Question 55.
Whirh acid is present in vinigar?
Answer:
Acetic acid.
Question 56.
Which acid is present in orange?
Answer:
Citric acid and ascorbic acid.
Question 57.
Which acid is present in lemon?
Answer:
Citric acid and ascorbic acid.
Question 58.
Where the maximum amount of Calcium lies in our body?
Answer:
99% of Calcium in our body is in our bones.
Question 59.
What is organic Sea-salt?
Answer:
A special type of salt is produced from pollution-free ocean source, known as organic Sea-salt.
Question 60.
What is the effect of reduced activity of thyroid glands on females?
Answer:
The reduced activity of thyroid gland: may lead to infertility in females.
Question 61.
Which acid is present in apple?
Answer:
Malic acid.
Question 62.
Which acid is present in tomato?
Answer:
Malic acid, oxalic acid and citric acid.
Question 63.
Which acid is present in sodawater?
Answer:
Carbonic acid.
Question 64.
Which acid is present in tamarind?
Answer:
Tartaric acid.
Question 65.
Which acid is present in curd?
Answer:
Lactic acid.
Question 66.
What is the role of vitamin D in our body?
Answer:
Regulates the absorption of calcium and phosphorous in the intestine, mineral deposition in bones and teeth.
Question 67.
What are the function of different enzymes present in our body?
Answer:
To initiate and speed up the bio-chemical reaction.
Question 68.
How does glucose produce energy in our body?
Answer:
Glucose is broken down by enzymes during digestion to produce energy in our body.
Short Questions & Answers : (2 marks for each question)
Question 1.
Why is iodized salt necessary for our body?
Answer:
lodine helps in maturation of brain, so it is essential for children. Moreover, deficieicy of iodine may lead to physical and mental depression and Goitre.
Question 2.
What is pH scale? How is it important?
Answer:
The strength of acidity or basicity of a solution is measured by pH scale.
At 25° C the pH of a neutral solution (e.g. water) is 7 . The solution having a pH less than 7 (upto zero) is acidic in nature. The solution having a pH greater than 7 (upto 14) is basic or alkaline.
Question 3.
What is thyroid gland?
Answer:
If you touch the sides of your vocal chord with fingers, you will find the presence of two small glands. These are thyroid glands.
Question 4.
What is Goitre?
Answer:
In case of iodine deficiency the thyroid glands get enlarged in trying to function normally. The throat get abnormallly swollen and this is known as Goitre.
Question 5.
What is soap?
Answer:
Soap is the Sodium or Potassium salt of some organic acids which are prepared from the reactions of Caustic Soda or Caustic Potash with fat or oils.
Fats or Oils + Caustic alkali → Soap + glycerine.
Question 6.
What is polymer?
Answer:
A polymer is a chemical compound with large molecules made of many smaller molecules of the same kind. Some polymers exist naturaly and other are produced in laboratories and factories.
Question 7.
What harm nylon net are causing in the environment?
Answer:
Offsprings of Hilsa fishes and baby turtles are dying in the nylon net with smaller gaps. Thus the biodiversities are being destroyed.
Question 8.
Why centent and sand-based construction need watering?
Answer:
In prisence of water the Calcium hyroxide water also adds to different silicate compounds of cement. As heat is liberated in these reactions, cement may be cracked. So concrete casting needs watering.
Long Questions & Answers : (3 marks for each question)
Question 1.
How is water helpful in human body?
Answer:
Water is the most important requirement for our survival. After several days without water lruman beings may die. Water helps us to transport the simple compounds generated by digestion of carbohydrates. lipids and proteins to different parts of our body. Harmful compounds formed in our body are excreted through urine, that is basically a watery fluid.
Question 2.
What are the two factors on which the acid-base balance of human body depends? Why it is necessary to maintain a fixed acid-base balance in human body?
Answer:
The acid-base balance of human body depends mainly on two factors –
a) Amount of carbon dioxide released by respirartion.
b) Different changes by chemical reactions occuring in our body.
It is necessary to maintain a fixed acid-base balance in human body because different parts of the body enamel of teeth. bone joint are affected and aging process may become faster.
Question 3.
What is the sources of Calcium that is essential for body?
Answer:
Food from animal origin e.g. – milk, curd, bones of small fishes etc.
Question 4.
Which organization established factories of iodized salt in different parts of the country? In which year the production of iodized salt became sufficient?
Answer:
Factories for the production of iodized salt in different parts of the country were established under the collaboration of WHO and UNICEF. In 1983 the production of iodized salt became sufficient for Indian population.
Question 5.
In most cases, mango or other fruit or vegetable slices are coated with common salt and dried in the sun, why?
Answer:
This is done due to two reasons.
(i) So that mango slices lose most of the water.
(ii) So that those pickles are protected from aerial germs for a long time.
Question 6.
Why salt is used to preserve food since antiquity?
Answer:
The germs when come in contact with sait, they lose cell fluid by osmosis. As a result the germs are killed, this helps topreserve food.
Question 7.
Give example of some natural polymer.
Answer:
The fibres in the plant body are madc up of different types of carbohydrate polymers. On the other hand, the muscles, tendons, ligaments etc of animal bodies are made up of proteins. which also are polymers.
Question 8.
How many types of plastics are there?
Answer:
Plastics can be classified into two types –
i) Thermo plastics : This type of plastic is soft and can be melted and remoulded repeatedly. Examples include polyethylene, polystarene and PVC.
ii) Thermosetting plastic: This type of plastic is hard and they can be melted and moulded only once. They cannot be melted and remoulded again. Examples include bakelite, melamine, teflon.
Question 9.
What are detergents?
Answer:
Detergents are water soluble compund of organic acids prepared by the reaction of hydrocarbon compounds from petroleum or other sources, and concentrated Sulphuric acid.The commercially available detergents are mixture of different compounds.
Question 10.
What are the harmful effects of DDT and other pesticides?
Answer:
It has been found that a breakdown product of DDT makes the eggshell of birds and tortoises thin and brittle. The egg breaks into pieces as the birds sit on them during into incubation. The pesticides have adverse effects on honeybees. silkworm and different types of birds. When consume with food, the pesticide also create different types of discases in human body.
Question 11.
What does glass consists of? What mixed compound is used to prepare yellow, blue and greeen coloured glass?
Answer:
Glass is a mixture that is prepared mainly from limestone, soda ash and sand.
Metallic oxides used to prepare coloured glasses are – Iron oxide is used for yellow glass, Cobalt oxide used for blue glass and Chromium oxide is used for green glass.
Question 12.
Define biodegradable and non-biodegradable wastes.
Answer:
The subtances that degrade or decompose through natural processes are known as biodegradable. Those that are not degraded like that are known as non-biodegradable.
The two types of wastes are – Entirely different in their structures and properties like water retaining ability etc. Animal bodies are completely biodegradable but manmade synthetic products are mostly non-biodegradable.
Question 13.
What are the general properties of common salt?
Answer:
- The colour of edible (common) salt is generally white.
- In-normal condition it is a hard substanee.
- Common salt is soluble in water.
- It is a crystalline solid.