Ncert Science Class 7 Solutions Chapter 4

Ncert Science Class 7 Solutions Chapter 4 Acids Bases and Salts

Welcome to NCTB Solutions. Here with this post we are going to help 7th class students for the Solutions of NCERT Class 7 Science Book Chapter 4, Acids Bases and Salts. Here students can easily find step by step solutions of all the questions in Acids Bases and Salts. Also our Expert Science Teacher’s solved all the problems with easily understandable language with proper guidance so that all the students can understand easily. Here in this post students will get chapter 4 solutions. Here all Question Answer are based on NCERT latest syllabus.

Acids Bases and Salts Exercise question Solutions :

(1) State differences between acids and bases.

Answer :

Difference between acids and bases are

  • Acids : 

(i) The acids are sour in taste.

(ii) The word acid has come from Latin word acere which means sour.

(iii) In the indicator test the acids changes the blue litmus into red color.

(iv) While the acids do not change color of the red litmus paper. Because it is meant only for alkaline test.

(v) Example : lemon , curd, etc.

  • Bases : 

(i) While the bases are bitter in taste.

(ii) And they feel soapy in touch.

(iii) In the indicator test the litmus does not changes the color.

(iv) When the bases are tested with red litmus paper they turn it blue.

(v) Example : lime water, baking soda, etc.

(2) Ammonia is found in many household products, such as window cleaners. It turns red litmus blue. What is its nature?

Answer :

Ammonia is found in many household products, such as window cleaners. It turns red litmus blue because it is basic in nature and not harsh, it is used for cleaning is used as refrigerant gas cleaning of water etc.

(3) Name the source from which litmus solution is obtained. What is the use of this solution?

Answer :

Litmus is an indicator which is observed from the litchens.

It is an indicator which is used to indicate nature of substance acid or base it is often absorbed on filter paper to produce oldest form of p h indicator.

(4) Is the distilled water acidic/basic/neutral? How would you verify it?

Answer :

The distilled water is neutral for these we can check by the litmus paper either red or blue and in both the condition the color remain unchanged the p h level of water is always neutral.

(5) Describe the process of neutralisation with the help of an example.

Answer :

The reaction between an acid and a base is known as neutralization. Salt and water are produced in this process with the evolution of heat. In our day to day life we overcome many neutralization and very easily for example we a person eats an food which is indigestible which contains acids that are not digesting so we neutralize them by taking a base contain substance when we get acidity we have baking soda pr milk or soda which contain bases.

(6) Mark ‘T’ if the statement is true and ‘F’ if it is false:

(i) Nitric acid turn red litmus blue.

Answer : 


Because the acid does not turns the red litmus blue because it is meant for an alkaline ph level.

(ii) Sodium hydroxide turns blue litmus red.

Answer :  


Because it is a base and it turns red litmus to blue.

(iii) Sodium hydroxide and hydrochloric acid neutralise each other and form salt and water.

Answer : 


(iv) Indicator is a substance which shows different colours in acidic and basic solutions.

Answer : 


(v) Tooth decay is caused by the presence of a base.

Answer :  


Because the tooth decay is caused by acidic substances and bases are used to clean it.

(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 neutral drink. How will Dorji decide which drink is to be served to whom?

Answer : 

As we know that the soft drinks are three types here acidic basic and neutral the neutral soft drink don’t have any taste and acidic drink have sour taste and basic drink has bitter taste . So the dorji can taste the few drops of the drinks and serve the drinks else he can also use the litmus paper test to recognize the nature of drinks. And serve them to his customer in his restaurant.

(8) Explain why :

(a) An antacid tablet is taken when you suffer from acidity

Answer : 

The antacid tablet contains bases like milk of magnesia which neutralize the acid produced in the stomach.

For example zyntac tablet.

(b) Calamine solution is applied on the skin when an ant bites.

Answer : 

Calamine contains zinc carbonate in itself which is basic in nature which neutralize the formic acid which injected by the ants to the body when they bite. Hence applied on skin.

(c) Factory waste is neutralised before disposing it into the water bodies.

Answer : 

Factory waste is neutralized before disposing it into water bodies because it may be acidic and harmful to aquatic animals so it is neutralized by the help of bases and then disposed.

(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 turmeric indicator.

Answer : 

(1) if the liquid is added with turmeric indicator and turns red then it is sodium hydroxide.

(2) if the liquid is added with turmeric indicator and is unchanged then it is sugar solution because it is neutral and at this stage no color change takes place.

(3) if the liquid added with turmeric indicator changes to blue color the liquid is hydrochloric acid.

(10) Blue litmus paper is dipped in a solution. It remains blue. What is the nature of the solution? Explain.

Answer :

The solution is either base or neutral if it was acidic it may change to red after dipping the blue litmus in solution. And bases don’t change the blue litmus paper color.


More Solutions : 

👉 Nutrition in Plants

👉 Nutrition in Animals

👉 Heat

Updated: June 30, 2023 — 5:28 am

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