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NCERT Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts are part of NCERT Solutions for Class 7 Science. Here we have given NCERT Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts.

NCERT Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts

Question 1.
State differences between acids and bases.
Answer:

 Question 2.
Ammonia is found in many household products, such as window cleaners. It turns red litmus blue. What is its nature?
Answer:
Ammonia has basic nature.

Question 3.
Name the source from which litmus solution is obtained. What is the use of this solution?
Answer:
The extraction of litmus solution takes place from Lichens (a symbiotic association of algae and fungi). It is used to determine whether the given solution is acidic or basic.

Question 4.
Is the distilled water acidic, basic, or neutral? How would you verify it?
Answer:
Distilled water is neutral. We can verify it by showing that neither blue nor red litmus paper changes its colour when dipped in it.

Question 5.
Describe the process of neutralization with the help of an example.
Answer:
The process in which an acid reacts with a base to form salt and water is known as a neutralization reaction. For example,

Question 6.
Mark ‘T’ if the statement is true and ‘F’ if it is false :
(i) Nitric acid turns red litmus blue. (T/F)
(ii) Sodium hydroxide turns blue litmus red. (T/F)
(iii) Sodium hydroxide and hydrochloric acid neutralize each other and form salt and water. (T/F)
(iv) Indicator is a substance which shows different colours in acidic and basic solutions. (T/F)
(v) Tooth decay is caused by the presence of a base. (T/F)
Answer:
(i) F
(ii) F
(iii) T
(iv) T
(v) F

Question 7.
Dorji has a few bottles of soft drink in his restaurant. But, unfortunately, these are not labelled. He has to serve the drinks on the demand of customers. One customer wants acidic drink, another wants basic and third one wants a neutral drink. How will Dorji decide which drink is to be served to whom?
Answer:
He can decide by the use of an indicator. If the sample of drink turns red litmus blue, it is basic. If it turns blue litmus red, it is acidic. If it does not affect litmus, it is neutral.

Question 8.
Explain why :
(a) An antacid tablet is taken when you suffer from acidity.
(b) Calamine solution is applied on the skin when an ant bites.
(c) Factory waste is neutralised before disposing it into the water bodies.
Answer:
(a) To relieve indigestion, we take an antacid such as milk of magnesia. It neutralizes the effect of excessive acid.
(b) When an ant bites, it injects the acidic liquid into the skin. This acidic liquid is formic acid, which leads to inflammation to the skin. The effect of the sting can be neutralised by rubbing calamine solution which contains zinc carbonate. The zinc carbonate is a weak base and causes no harm to the skin.
(c) The wastes of many factories usually contain acids. If they are allowed to flow into the water bodies without neutralising it properly, then the acids will kill fish and other aquatic organisms. So factory wastes must be neutralised by adding some basic substances into the wastes before disposing these into water bodies.

Question 9.
Three liquids are given to you. One is hydrochloric acid, another is sodium hydroxide and third is a sugar solution. How will you identify them? You have only a turmeric indicators.
Answer:

Question 10.
Blue litmus paper is dipped in a solution. It remains blue. What is the nature of the solution? Explain.
Answer:
The solution may be neutral or basic. Both types of substances have no effect on blue litmus. Put a drop of this solution on a red litmus paper. If it turns blue, then the above solution is basic in nature and if no colour change occurs, then it is neutral.

Question 11.
Consider the following statements:
(a) Both acids and bases change colour of all indicators.
(b) If an indicator gives a colour change with an acid, it does not give a change with a base.
(c) If an indicator changes colour with a base, it does not change colour with an acid.
(d) Change of colour in acid, and a base depends on the type of the indicator.
Which of these statements are correct?
(i) All four
(ii) (a) and (d)
(iii) (b) and (c)
(iv) Only (d)
Answer:
(ii) (a) and (d)

We hope the NCERT Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts help you. If you have any query regarding NCERT Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts, drop a comment below and we will get back to you at the earliest.

NCERT Solutions for Class 7 Science Chapter 4 Heat are part of NCERT Solutions for Class 7 Science. Here we have given NCERT Solutions for Class 7 Science Chapter 4 Heat.

NCERT Solutions for Class 7 Science Chapter 4 Heat

Question 1.
State similarities and differences between the laboratory thermometer and the clinical thermometer.
Answer:
Similarities:

1. Both contain mercury in bulbs.
2. Both use the Celsius scale on a glass tube.

Differences:

1. The temperature on the laboratory thermometer falls by itself, but not so in the clinical thermometer.
2. The range of a laboratory thermometer is much higher than a clinical thermometer.

Question 2.
Give two examples each of conductors and insulators of heat.
Answer:

• Conductors of heat: Copper, iron.
• Insulators: Plastic, wood (dry).

Question 3.
Fill in the blanks:

1. The hotness of an object is determined by its …….
2. The temperature of boiling water cannot be measured by a ………. thermometer.
3. Temperature is measured in degree …………
4. No medium is required for transfer of heat by the process of ………..
5. A cold steel spoon is dipped in a cup of hot milk. It transfers heat to its other end by the process of ………
6. Clothes of ……….. colours absorb heat better than clothes of light colours.

Answer:

1. temperature
2. clinical
3. Celsius
4. radiation
5. conduction
6. dark

Question 4.
Match the following:

Answer:

Question 5.
Discuss why wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing.
Answer:
If there are more than one layer of clothes, air would be trapped in between them. Air is a poor conductor of heat. This increases the insulation and thus comfortability of the clothes as a whole.

Question 6.
Look at Fig., mark where the heat is being transferred by conduction, by convection, and by radiation.

Fig. Heat transferred by conduction, by convection and by radiation
Answer:
In this figure, the heat is transferred at three points in different ways:

• by radiation: from the flame to the bottom of the pan.
• by conduction: from lower surface to upper surface of the pan.
• by convection: from the base to the upper region of pan water.

Question 7.
In places of the hot climate, it is advised that the outer walls of houses be painted white. Explain.
Answer:
Objects with white surfaces reflect more heat and absorb less. So, less heat from outside would enter the house.

Question 8.
One liter of water at 30°C is mixed with one liter of water at 50°C. The temperature of the mixture will be
(a) 80°C
(b) more than 50°C but less than 80°C
(c) 20°C
(d) between 30°C and 50°C
Answer:
(d) between 30°C and 50°C.

Question 9.
An iron ball at 40°C is dropped in a mug containing water at 40°C. The heat will
(a) flow from the iron ball to water.
(b) not flow from iron ball to water or from water to iron ball.
(c) flow from water to iron ball.
(d) increase the temperature of both.
Answer:
(b) not flow from iron ball to water or from water to iron ball.

Question 10.
A wooden spoon is dipped in a cup of ice cream. Its other end
(a) becomes cold by the process of conduction.
(b) becomes cold by the process of convection.
(c) becomes cold by the process of radiation.
(d) does not become cold,
Answer:
(d) does not become cold.

Question 11.
Stainless steel pans are usually provided with copper bottoms. The reason for this could be that
(a) copper bottom makes the pan more durable.
(b) such pans appear colourful.
(c) copper is a better conductor of heat than stainless steel.
(d) copper is easier to clean than stainless steel.
Answer:
(c) copper is a better conductor of heat than stainless steel.

We hope the NCERT Solutions for Class 7 Science Chapter 4 Heat help you. If you have any query regarding NCERT Solutions for Class 7 Science Chapter 4 Heat, drop a comment below and we will get back to you at the earliest.

NCERT Solutions for Class 7 Science Chapter 3 Fibre to Fabric are part of NCERT Solutions for Class 7 Science. Here we have given NCERT Solutions for Class 7 Science Chapter 3 Fibre to Fabric.

NCERT Solutions for Class 7 Science Chapter 3 Fibre to Fabric

Question 1.
You must be familiar with the following nursery rhymes:
(i) ‘Baa baa black sheep, have you any wool.
(ii) ‘Mary had a little lamb, whose fleece was white as snow.
Answer the following:
(a) Which parts of the black sheep have wool?
(b) What is meant by the white fleece of the lamb?
Answer:
(a) The hairy skin – called fleece, has wool in black sheep.
(b) White fleece means hairy skin which is white in colour.

Question 2.
The silkworm is (a) a caterpillar, (b) a larva. Choose the correct option.
(i) (a)
(ii) (b)
(iii) both (a) and (b)
(iv) neither (a) nor (b)
Answer:
(iii) both (a) and (b)

Question 3.
Which of the following does not yield wool?
(i) Yak
(ii) Camel
(iii) Goat
(iv) Woolly dog
Answer:
(iv) Woolly dog

Question 4.
What is meant by the following terms?

1. Rearing
2. Shearing
3. Sericulture

Answer:

1. Rearing: Bringing up and looking after the sheep is called rearing.
2. Shearing: To obtain wool, the fleece of the sheep along with a thin layer of skin is removed from its body. This process is called shearing.
3. Sericulture: The rearing of silkworms for obtaining silk is called sericulture.

Question 5.
Given below is a sequence of steps in the processing of wool. Which are the missing steps? Add them.
Shearing, ……., sorting ………, ………., ……….
Answer:
Shearing, scouring, sorting, picking out burrs, colouring, rolling.

Question 6.
Make sketches of the two stages in the life history of the silk moth which are directly related to the production of silk.
Answer:

Question 7.
Out of the following, which are the two terms related to silk production?
Sericulture, floriculture, moriculture, apiculture and silviculture.
Hints:
(i) Silk production involves the cultivation of mulberry leaves and rearing silkworms.
(ii) Scientific name of mulberry is Morus alba.
Answer:
Sericulture, Moriculture.

Question 8.
Match the words of Column I with those given in Column II:

Answer:

Question 9.
Given below is a crossword puzzle based on this lesson. Use hints to fill in the blank spaces with letters that complete the words.

Down
(D) 1 : Thorough washing
2 : Animal fibre
3 : Long thread like structure
Across
(A) 1 : Keeps warm
2 : Its leaves are eaten by silkworms
3 : Hatches from egg of moth
Answer:

We hope the NCERT Solutions for Class 7 Science Chapter 3 Fibre to Fabric help you. If you have any query regarding NCERT Solutions for Class 7 Science Chapter 3 Fibre to Fabric, drop a comment below and we will get back to you at the earliest.

NCERT Solutions for Class 8 Science Chapter 18 Pollution of Air and Water are part of NCERT Solutions for Class 8 Science. Here we have given NCERT Solutions for Class 8 Science Chapter 18 Pollution of Air and Water.

NCERT Solutions for Class 8 Science Chapter 18 Pollution of Air and Water

NCERT TEXTBOOK EXERCISES

Question 1.
What are the different ways in which water gets contaminated?
Answer.
Water gets contaminated due to the addition of substances harmful to health. Sewage, agricultural chemicals, and industrial waste are some of the major contaminants of water.

Question 2.
At an individual level, how can you help to reduce air pollution?
Answer.
At the individual level we can do the following things to reduce air pollution:

1. Use CNG and unleaded petrol instead of ordinary petrol and diesel.
2. Use public transport as far as possible.
3. Generate awareness about air pollution among the members of our family and friends.
4. We can plant trees and nurture the ones already present in the neighborhood.

Question 3.
Clear, transparent water is always fit for drinking. Comment.
Answer.
No, water which looks clean may still have disease-carrying microorganisms and dissolved impurities. Hence, it is not always fit for drinking, so it is essential to purify water before drinking, say for example by boiling process.

Question 4.
You are a member of the municipal body of your town. Make a list of measures that would help your town to ensure the supply of clean water to all its residents.
Answer.
Following are some of the measures that would help our town to ensure the supply of clear water to all its residents:

1. Make the supply system leakproof as a lot of drinking water is being wasted through the leakages.
2. Proper cleaning of the water tank from time to time.
3. Chlorine tablets should be made available.
4. The water supply pipes should not come in contact with the sewage pipes.

Question 5.
Explain the differences between pure air and polluted air.
Answer.
Pure air is free from any pollutant, has no smell, is soothing, and not irritating to the eyes. Whereas polluted air gives a filthy smell and people cannot breathe in ut. If people inhale such (impure or polluted) air, they may suffer from various breathing, heart, and lung problems. Even sometimes people die inhaling polluted air.

Question 6.
Explain circumstances leading to acid rain. How does acid rain affect us?
Answer.
Pollutants like sulphur dioxide and nitrogen dioxide react with the water vapour present in the atmosphere to form sulphuric acid and nitric acid. These come down with the rain, making the rain acidic. This is called acid rain.
Acid rain affects us in many ways, e.g.

1. Acid rain removes basic nutrients such as calcium from the soil.
2. Acid rain increases the corrosion of metals.
3. Acid rain damages buildings and sculptural materials.
4. The low pH of add rainwater changes the rate of metabolism of some organisms.
5. Add rain causes damage to freshwater life, e.g., decrease in fish population of lakes.
6. Add mists cause direct damage to the leaves of plants.

Question 7.
Which of the following is not a greenhouse gas?
(a) Carbon dioxide
(b) Sulphur dioxide
(c) Methane
(d) Nitrogen
Answer.
(d) Nitrogen

Question 8.
Describe the ‘Green House Effect’ in your own words.
Answer.
The sun’s rays when fall on the earth’s surface, warm it. Some of the sun’s rays are absorbed by the earth’s surface and left out rays are reflected back into space. Some of these rays are trapped by gases like C0₂, methane, etc. in the atmosphere, and these are not allowed to go out of the earth’s atmosphere.

These trapped rays begin to warm the earth’s surface. This causes heating of the earth’s atmosphere. This effect is named the Greenhouse effect because this is exactly like the greenhouse effect in a nursery.

Question 9.
Prepare a brief speech on global warming. You have to deliver the speech in your class.
Answer.
Today, global warming has appeared as one of the most severe threats to humankind. On one hand, carbon dioxide is added to the atmosphere due to human activities, by the other, as forest areas are also decreasing.

Question 10.
Describe the threat to the beauty of the Taj Mahal.
Answer.
Over the past 2 decades, India’s most famous tourist attraction, the Taj Mahal located at Agra, has become a matter of great concern. Experts have warned that air pollution is discolouring its white marble. So it is not only living organisms that get affected by polluted air but also the non-living things like buildings, monuments, and statues that are going to be affected.

The industries located in and around Agra like rubber processing, automobiles, chemicals and especially, the Mathura Oil Refinery have been responsible for producing pollutants like sulphur dioxide and nitrogen dioxide. These gases react with the water vapour present in the atmosphere to form sulphuric acid and nitric acid. These come down with the rain, making the rain acidic. This is called acid rain. Acid rain has resulted in corrosion of the marble of the monument. The phenomenon is also called “Marble cancer”. Suspended particulate matter, such as the soot particle emitted by the Mathura oil refinery, has contributed to the yellowing of the marble.

The Supreme Court has taken several steps to save the Taj Mahal. It has issued orders for the industries to either switch to cleaner fuels like CNG (Compressed Natural Gas) and LPG (Liquefied Petroleum Gas) or to move to faraway places. Moreover, the automobiles should switch over to unleaded petrol in the Taj Mahal Zone.

Question 11.
Why does the increased level of nutrients in the water affect the survival of aquatic organisms?
Answer.
Chemicals used as fertilizers in agriculture dissolve in water and are washed away into water bodies from the field. The excessive quantities of chemicals like nitrates and phosphates which are present in fertilisers act as nutrients for algae to flourish. Once these algae die, they serve as food for decomposers like bacteria. They use up a lot of oxygen. This results in a decrease in the oxygen level which is harmful to the survival of other organisms.

We hope the NCERT Solutions for Class 8 Science Chapter 18 Pollution of Air and Water help you. If you have any query regarding NCERT Solutions for Class 8 Science Chapter 18 Pollution of Air and Water, drop a comment below and we will get back to you at the earliest.

NCERT Solutions for Class 7 Science Chapter 2 Nutrition in Animals are part of NCERT Solutions for Class 7 Science. Here we have given NCERT Solutions for Class 7 Science Chapter 2 Nutrition in Animals.

NCERT Solutions for Class 7 Science Chapter 2 Nutrition in Animals

Question 1.
Fill in the blanks:

1. The main steps of nutrition in humans are ……., ………., ………., ………, and ………….
2. The largest gland in the human body is ………..
3. The stomach releases hydrochloric acid and ……… juices which act on the food.
4. The inner wall of the small intestine has many finger-like outgrowths called ……….
5. Amoeba digests its food in the ………..

Answer:

1. ingestion, digestion, absorption, assimilation, and egestion.
2. liver
3. digestive
4. villi
5. food vacuole.

Question 2.
Mark ‘T’ if the statement is true and ‘F’ if it is false:

1. Digestion of starch starts in the stomach. (T/F)
2. The tongue helps in mixing food with saliva. (T/F)
3. The gall bladder temporarily stores bile. (T/F)
4. The ruminants bring back swallowed grass into their mouth and chew it for some time. (T/F)

Answer:

1. F
2. T
3. T
4. T

Question 3.
Tick (√) mark the correct answer in each of the following:
(a) Fat is completely digested in the
(i) stomach
(ii) mouth
(iii) small intestine
(iv) large intestine

(b) Water from the undigested food is absorbed mainly in the
(i) stomach
(ii) food pipe
(iii) small intestine
(iv) large intestine
Answer:
(a) (iii) Small intestine
(b) (iv) Large intestine.

Question 4.
Match the items of Column I with those given in Column II:

Answer:

Question 5.
What are villi? What are their location and function?
Answer:
The inner walls of the small intestine have thousands of finger-like outgrowths. These are called villi. Villi are located in the small intestine. The villi increase the surface area for absorption of the digested food. Each villus has a network of thin and small blood vessels close to its surface. The surface of the villi absorbs the digested food materials.

Question 6.
Where is the bile produced? Which component of the food does it help to digest?
Answer:
Bile is produced in the liver. The bile juice is stored in a sac called the gall bladder. Bile plays an important role in the digestion of fats.

Question 7.
Name the type of carbohydrate that can be digested by ruminants but not by humans. Give the reason also.
Answer:
Cellulose is a type of carbohydrate that can be digested by ruminants but not by humans. Ruminants have a large sac-like structure called rumen which is present in between the small intestine and large intestine. The cellulose is digested here by the action of certain bacteria which are not present in humans.

Question 8.
Why do we get instant energy from glucose?
Answer:
Because glucose can easily breakdown in the cell with the help of oxygen and gives carbon dioxide, water, and energy.

Question 9.
Which part of the digestive canal is involved in:

1. absorption of food ……..
2. chewing of food …….
3. the killing of bacteria …….
4. complete digestion of food ………
5. formation of faeces ……..

Answer:

1. Small intestine
2. Mouth
3. Stomach
4. Small intestine
5. Large intestine.

Question 10.
Write one similarity and one difference between the nutrition in amoeba and human beings.
Answer:

1. Similarity: Both amoeba and humans use digestive juices to digest food.
2. Difference: Human needs to chew food, whereas, an amoeba, there is no chewing.

Question 11.
Match the items of Column I with suitable items in Column II

Answer:

 Question 12.
Label figure of the digestive system.
Answer:

Fig. Human digestive system

Question 13.
Can we survive only on raw, leafy vegetables/grass? Discuss.
Answer:
No. Because to live a healthy life, we need a complete balance of all nutrients. Raw leafy vegetables/grass may have cellulose which can not be digested by us. So, we cannot survive only on raw, leafy vegetables/grass.

We hope the NCERT Solutions for Class 7 Science Chapter 2 Nutrition in Animals help you. If you have any query regarding NCERT Solutions for Class 7 Science Chapter 2 Nutrition in Animals, drop a comment below and we will get back to you at the earliest.