---
title: "NCERT Solutions for Class 8 Science Chapter 7 Exercise 7.7"
url: https://www.swavid.com/science/class/8/chapter/particulate-nature-of-matter/ncert-solutions/exercise-7-7
dateModified: 2026-10-07T16:14:45+00:00
---

# NCERT Solutions for Class 8 Science Chapter 7 Exercise 7.7

Chapter 7: Particulate Nature of Matter. Every question from Exercise 7.7, with full working and the final answer.

Free PDF (13 pages): https://www.swavid.com/api/seo/pdf/ncert/science/class-8/swavid-ncert-solutions-class-8-science-chapter-7-particulate-nature-of-matter-7cb91bb328.pdf

## Activity 7.7: Let us observe

### Question 1

*Activity*

What difference do you observe in the water levels?

**Solution**

1. Initially, when sugar is added to water, the water level rises.
2. After stirring and complete dissolution of sugar, the water level decreases to some extent.
3. This indicates that there is space between water particles, and the dissolved sugar particles occupy these interparticle spaces without significantly increasing the total volume.

**Answer:** The water level rises initially on adding sugar, but after dissolution, it decreases slightly as sugar particles occupy the interparticle spaces between water particles.

> Common mistake: Thinking that the total volume of a solution is always equal to the sum of the volumes of the solute and solvent.

### Question 2

*Activity*

What do you observe in each case? Do the sand particles dissolve? Does the volume of water in the vessel change after mixing, and why?

**Solution**

1. Soluble solids like common salt or glucose dissolve in water by occupying the spaces between water particles, keeping the volume change minimal.
2. Insoluble solids like sand do not dissolve in water; their particles simply settle down at the bottom.
3. When sand is added, the sand particles occupy space in the container alongside water, causing the total volume to increase.

**Answer:** Soluble solids dissolve and occupy interparticle spaces with little volume change, whereas insoluble solids like sand do not dissolve, settle down, and cause the total volume to increase.

> Common mistake: Assuming all solids dissolve in water and behave the same way.

## Related pages

- [All Chapter 7 NCERT solutions](https://www.swavid.com/science/class/8/chapter/particulate-nature-of-matter/ncert-solutions)
- [Exercise 7.1](https://www.swavid.com/science/class/8/chapter/particulate-nature-of-matter/ncert-solutions/exercise-7-1)
- [Exercise 7.2](https://www.swavid.com/science/class/8/chapter/particulate-nature-of-matter/ncert-solutions/exercise-7-2)
- [Exercise 7.3](https://www.swavid.com/science/class/8/chapter/particulate-nature-of-matter/ncert-solutions/exercise-7-3)
- [Exercise 7.4](https://www.swavid.com/science/class/8/chapter/particulate-nature-of-matter/ncert-solutions/exercise-7-4)
- [Exercise 7.6](https://www.swavid.com/science/class/8/chapter/particulate-nature-of-matter/ncert-solutions/exercise-7-6)
- [Exercise 7.8](https://www.swavid.com/science/class/8/chapter/particulate-nature-of-matter/ncert-solutions/exercise-7-8)
- [Exercise 7.9](https://www.swavid.com/science/class/8/chapter/particulate-nature-of-matter/ncert-solutions/exercise-7-9)

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