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

NCERT solutions for class 7 science chapter 5 Acids Bases And Salts: Generally acids are sour in taste and bases have a bitter taste and are soapy in touch. To test whether the given substances are acid, base or salt, indicators are used. Concepts can be better understood with the help of the solutions of NCERT class 7 science chapter 5 acids bases and salts. Different types of indicators and their usage are discussed with the help of experiments. Questions based on testing of acids and bases using indicators are discussed in the CBSE NCERT solutions for class 7 science chapter 5 acids bases and salts. The concept of neutralisation and their applications in daily life is one of the important topics of the NCERT science chapter 5. There are a total of 11 questions explained in the NCERT solutions for class 7 science chapter 5 acids bases and salts. Practising the questions from solutions of NCERT helps in scoring good marks in the exams

## Here are the important topics of NCERT class 7 science chapter 5 acids bases and salts mentioned below:

5.1 Acids and Bases

5.2 Natural Indicators Around Us

Litmus: a Natural Dye

Turmeric is Another Natural Indicator

China Rose as an Indicator

5.3 Neutralisation

5.4 Neutralisation in Everyday Life

Indigestion

Ant Bite

Soil Treatment

Factory Wastes

## NCERT solutions for class 7 science chapter 5 acids bases and salts exercise:

1. State differences between acids and bases.

Differences between acids and bases are given below:

 Acids Bases 1 Turns blue litmus paper to red Turns red litmus paper to blue 2 They are sour in test They are bitter in test 3 Acids do not change the colour of turmeric indicator They change the colour of turmeric indicator 4 They are not soapy in touch They are soapy in touch 5 Eg:- HCL Eg:- NaOH

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

Bases turn the colour of red litmus to blue and as ammonia also turns the colour of red litmus to blue.
Therefore,  ammonia is basic in nature

Litmus solution is commonly obtained from lichens. A natural dye which is extracted from lichens is dissolved in distilled water to form a litmus solution. Litmus solution is used as an indicator to distinguish between acids and bases.

When we add an acidic solution to it, it turns red and when we add a basic solution to it, it turns blue.

4. Is the distilled water acidic/basic/neutral?

How would you verify it?

Nature of distilled water is neutral. Because when we will test it with a litmus paper it does not change the colour of it and turns neither into red nor in blue colour.
Therefore, we can say that distilled water is neutral in nature.

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

The reaction between an acid and a base is known as neutralization reaction. In such type of reactions, acid and base reacts with each other and cancel out each other's effect and formation of salt and water takes place and energy in the form of heat is evolved.

$Acid + Base \rightarrow Salt + Water + Heat$

For eg.
Sodium hydroxide $(NaOH)$ reacts with hydrochloric acid  $(HCI)$ to give sodium chloride $(NaCl)$  and water$(H_20)$with evo of some heat..

$NaOH + HCl \rightarrow NaCl +H_2O+Heat$

If Dorji has litmus paper or solution then with the help of that he can distinguish between them by putting one drop of each drink on litmus paper. If the colour of the litmus paper changes to blue, then it is a basic drink and if the colour of the litmus paper changes to red, then it is an acidic drink and if no change in colour then it is neutral.
Another method is he can distinguish between them by tasting the drinks. Drink with sour taste is acidic whereas drink with bitter taste is basic and neutral drinks will have no taste.

8 (a). Explain why:

An antacid tablet is taken when you suffer from acidity.

This is because antacids are the substance that neutralizes the excess of acids which is produced in the stomach during acidity as it contains base, such as milk of magnesia.

These bases react with the excess amount of acids and neutralize their effect and giving us relief.

8 (b). Explain why:

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

The sting of an ant contains formic acid. Therefore, when an ant bites, it injects formic acid into our skin and due to which we feel a  burning sensation. As calamine solution contains zinc carbonate which is basic in nature.

Therefore, when we applied it on the skin it neutralizes the effect of formic acid.

8 (c). Explain why:

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

Wastes materials in factories contain acids. Therefore, if we threw them directly into water bodies then the water becomes acidic and harm aquatic lives.

Therefore, these factory wastes are neutralized with basic chemicals before disposing to water bodies.

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.

When we place turmeric solution in contact with bases it turns into red colour and generally It is not affected by acids and neutral substances.

Now, we can distinguish between hydrochloric acid, sodium hydroxide and a sugar solution by applying turmeric solution to three test tubes, we will observe that

(1) test tube A (Hydrochloric acid): No change in colour will take place because turmeric is not affected by acids.

(2) test tube B (sodium hydroxide): Turmeric solution will change its colour to red because turmeric solution changes its colour to red when we place it in contact with bases.

(3) test tube c (sugar solution): No change in color will take place because sugar solution is neither basic nor acidic in nature
Therefore, we are only able to identify basic solution using turmeric as an indicator

We know that blue litmus paper turns into red colour when coming in contact with an acidic solution and basic and neutral solutions do not change the color of blue litmus paper. Since blue litmus paper remains blue after it is dipped in a solution.

Therefore, the solution is either basic or neutral in nature.

## Chapterwise NCERT solutions of class 7 science

 Chapter No. Chapter Name Chapter 1 NCERT solutions for class 7 science chapter 1 Nutrition in Plants Chapter 2 Solutions of NCERT class 7 science chapter 2 Nutrition in Animals Chapter 3 CBSE NCERT solutions for class 7 science chapter 3 Fibre to Fabric Chapter 4 NCERT solutions for class 7 science chapter 4 Heat Chapter 5 NCERT solutions for class 7 science chapter 5 Acids Bases and Salts Chapter 6 CBSE NCERT solutions for class 7 science chapter 6 Physical and Chemical Changes Chapter 7 NCERT solutions for class 7 science chapter 7 Weather Climate and Adaptations of Animals to Climate Chapter 8 Solutions of NCERT class 7 science chapter 8 Winds storms and cyclones Chapter 9 CBSE NCERT solutions for class 7 science chapter 9 Soil Chapter 10 NCERT solutions for class 7 science chapter 10 Respiration in Organisms Chapter 11 Solutions of NCERT class 7 science chapter 11 Transportation in Animals and Plants Chapter 12 CBSE NCERT solutions for class 7 science chapter 12 Reproduction in Plants Chapter 13 NCERT solutions for class 7 science chapter 13 Motion and Time Chapter 14 Solutions of NCERT class 7 science chapter 14 Electric Current and its Effects Chapter 15 CBSE NCERT solutions for class 7 science chapter 15 Light Chapter 16 NCERT solutions for class 7 science chapter 16 Water A Precious Resource Chapter 17 Solutions of NCERT class 7 science chapter 17 Forests Our Lifeline Chapter 18 CBSE NCERT solutions for class 7 science chapter 18 Wastewater Story

## Benefits of NCERT solutions for class 7 science chapter 5 acids bases and salts:

• Testing using indicators is an important topic of the chapter. To familiarise with this concept there are many questions discussed in the CBSE NCERT solutions for class 7 science chapter 5 acids bases and salts.
• The NCERT solutions for class 7 science chapter 5 acids bases and salts help students to solve homework problems of the chapter.

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