---
title: "NCERT Solutions for Class 7 Science Chapter 2 Exercise 2.4"
url: https://www.swavid.com/science/class/7/chapter/exploring-substances-acidic-basic-and-neutral/ncert-solutions/exercise-2-4
dateModified: 2026-10-07T16:06:22+00:00
---

# NCERT Solutions for Class 7 Science Chapter 2 Exercise 2.4

Chapter 2: Exploring Substances: Acidic, Basic, and Neutral. Every question from Exercise 2.4, with full working and the final answer.

Free PDF (16 pages): https://www.swavid.com/api/seo/pdf/ncert/science/class-7/swavid-ncert-solutions-class-7-science-chapter-2-exploring-substances-acidic-basic-and-neutral-13aedb74b7.pdf

## Activity 2.4: Let us find out

### Question 1

*Activity*

Observe and record any colour changes to the extract in Table 2.3.

**Solution**

1. Add lemon juice to red rose extract in test tube A and observe the colour change to red.
2. Add soap solution to red rose extract in test tube B and observe the colour change to green.

**Answer:** Red rose extract turns red in lemon juice and green in soap solution.

### Question 2

*Activity*

Repeat the same with the other samples used in Activity 2.1 and record your observations in Table 2.3.

**Solution**

1. Take drops of other samples from Activity 2.1 such as amla juice, vinegar, baking soda solution, and lime water.
2. Add them separately to red rose extract and record the resulting colour changes in Table 2.3.

**Answer:** Acidic samples turn red rose extract red, and basic samples turn it green.

### Question 3

*3 marks · Short answer*

Are the samples that change the colour of the flower extract to a shade of red the same as those that changed the colour of blue litmus paper to red? (Group A, Table 2.2)

**Solution**

1. Samples in Group A (such as lemon juice, amla juice, tamarind water, and vinegar) turn blue litmus paper to red, showing they are acidic.
2. These same acidic substances change the colour of the red rose extract to a shade of red.
3. Therefore, the samples that turn the flower extract red are the same as those that turn blue litmus paper to red.

**Answer:** Yes, the samples that change the flower extract to red are the same as those that turn blue litmus paper to red.

> Common mistake: Confusing the colour changes of acidic and basic substances with indicators.

### Question 4

*3 marks · Short answer*

Are the samples that change the colour of the flower extract to a shade of green the same as those that changed the colour of red litmus paper to blue? (Group B, Table 2.2)

**Solution**

1. Samples in Group B (such as soap solution, baking soda solution, lime water, and washing powder solution) turn red litmus paper to blue, showing they are basic.
2. These same basic substances change the colour of the red rose extract to a shade of green.
3. Therefore, the samples that turn the flower extract green are the same as those that turn red litmus paper to blue.

**Answer:** Yes, the samples that change the flower extract to green are the same as those that turn red litmus paper to blue.

> Common mistake: Stating that bases turn red rose extract blue instead of green.

### Question 5

*3 marks · Short answer*

Are the samples that do not change the colour of the flower extract the same as those that did not change the colour of red and blue litmus papers? (Group C, Table 2.2)

**Solution**

1. Samples in Group C (such as tap water, sugar solution, and salt solution) do not change the colour of either red or blue litmus paper because they are neutral.
2. These same neutral substances do not change the colour of the red rose extract.
3. Therefore, the samples that do not change the colour of the flower extract are the same as those that do not affect red and blue litmus papers.

**Answer:** Yes, the samples that do not change the colour of the flower extract are the same as those that do not affect red and blue litmus papers.

> Common mistake: Assuming neutral substances cause a colour change in natural indicators.

### Question 6

*3 marks · Short answer*

Can you now fill in the nature of the substances in Table 2.3?

**Solution**

1. Identify the colour produced by each sample when added to the red rose extract.
2. Classify samples that give a red shade as acidic in nature.
3. Classify samples that give a green shade as basic in nature, thereby completing Table 2.3.

**Answer:** Acidic samples are marked as acidic, and basic samples are marked as basic based on the red rose extract test.

> Common mistake: Incorrectly assigning acidic or basic nature without checking the observed indicator colour.

## Related pages

- [All Chapter 2 NCERT solutions](https://www.swavid.com/science/class/7/chapter/exploring-substances-acidic-basic-and-neutral/ncert-solutions)
- [Exercise 2.1](https://www.swavid.com/science/class/7/chapter/exploring-substances-acidic-basic-and-neutral/ncert-solutions/exercise-2-1)
- [Exercise 2.2](https://www.swavid.com/science/class/7/chapter/exploring-substances-acidic-basic-and-neutral/ncert-solutions/exercise-2-2)
- [Exercise 2.5](https://www.swavid.com/science/class/7/chapter/exploring-substances-acidic-basic-and-neutral/ncert-solutions/exercise-2-5)
- [Exercise 2.6](https://www.swavid.com/science/class/7/chapter/exploring-substances-acidic-basic-and-neutral/ncert-solutions/exercise-2-6)
- [Exercise 2.7](https://www.swavid.com/science/class/7/chapter/exploring-substances-acidic-basic-and-neutral/ncert-solutions/exercise-2-7)

Solutions written by SwaVid, a personal AI tutor for Class 6 to 10 Maths and Science. Practise this chapter free: https://www.swavid.com/start/student