Class 7 Science - Chapter Acids, Bases and Salts NCERT Solutions | Mark ‘T’ if the statement is
Mark ‘T’ if the statement is true and ‘F’ if it is false:
(i) Nitric acid turn red litmus blue. (T/F)
(ii) Sodium hydroxide turns blue litmus red. (T/F)
(iii) Sodium hydroxide and hydrochloric acid neutralise 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)
(i) Answer: False
Nitric acid is not right to turn the red litmus paper into blue. The explanation is that the colour of the paper does not change when an acid comes into contact with a red litmus paper. Only if an acid comes into contact with blue litmus paper will the colour of the litmus paper change into red. Nitric acid is an acid so it does not turns the litmus paper into blue.
(ii) Answer: False
This statement is false because sodium hydroxide is not an acid, it is base which turns red litmus to blue.
(iii) Answer: True
When acid and base reacts with each other, they form an neutral substance, this process is called neutralisation. When the solution of sodium hydroxide (a base) and hydrochloric acid (an acid) is mixed in test tube in proper ratio, both neutralize each other.
(iv) Answer: True
This statement is true because different solution show different colours in acidic or basic medium. Indicators are chemical compounds that change Colour according to pH of the solution they are put in. They are used to determine pH of the body (acidity/basicity).
(v) Answer: False
This statement is false because tooth decay is caused by acids which is formed in our mouth when the food particles left over all night. They constantly damage tooth enamel and thus cause tooth decay.
More Questions From Class 7 Science - Chapter Acids, Bases and Salts
- Q:-
Blue litmus paper is dipped in a solution. It remains blue. What is the nature of the solution? Explain.
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Is the distilled water acidic/basic/neutral? How would you verify it?
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Ammonia is found in many household products, such as window cleaners. It turns red litmus blue. What is its nature?
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Describe the process of neutralisation with the help of an example.
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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 an 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 - Q:-
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 neutral drink. How will Dorji decide which drink is to be served to whom?
- Q:-
Name the source from which litmus solution is obtained. What is the use of this solution?
- Q:-
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 turmeric indicator.
- Q:-
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. - Q:-
State differences between acids and bases.
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(a) Photosynthesis
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(c) Burning of coal
(d) Melting of wax
(e) Beating aluminium to make aluminium foil
(f ) Digestion of food - Q:-
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(a) Wind is——————air.
(b) Winds are generated due to —————— heating on the earth.
(c) Near the earth’s surface __________air rises up whereas ___________ air comes down.
(d) Air moves from a region of ——— pressure to a region of ———. - Q:-
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(i) air and water
(ii) water and plants
(iii) minerals, organic matter, air and water
(iv) water, air and plants - Q:-
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Column I Column II
(i) Stomata (a) Absorption of water
(ii) Xylem (b) Transpiration
(iii) Root hairs (c) Transport of food
(iv) Phloem (d) Transport of water
(e) Synthesis of carbohydrates - Q:-
Fill in the blanks:
(a) Production of new individuals from the vegetative part of parent is called_____________.
(b) A flower may have either male or female reproductive parts. Such a flower is called_____________.
(c) The transfer of pollen grains from the anther to the stigma of the same or of another flower of the same kind is known as _____________.
(d) The fusion of male and female gametes is termed as _____________.
(e) Seed dispersal takes place by means of _____________, _____________ and _____________. - Q:-
Classify the following as motion along a straight line, circular or oscillatory motion:
(i) Motion of your hands while running.
(ii) Motion of a horse pulling a cart on a straight road.
(iii) Motion of a child in a merry-go-round.
(iv) Motion of a child on a see-saw.
(v) Motion of the hammer of an electric bell.
(vi) Motion of a train on a straight bridge. - Q:-
Why do organisms need to take food?
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Hints:
(i) Silk production involves cultivation of mulberry leaves and rearing silkworms.
(ii) Scientific name of mulberry is Morus alba. - Q:-
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Column I Column II
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