MEDIUM
8th Kerala Board
IMPORTANT
Earn 100

Soap decreases the surface tension of water.

How does the decrease in surface tension benefit washing of clothes?

Important Questions on Water

HARD
8th Kerala Board
IMPORTANT
Science for Class 8 - Part 2>Chapter 5 - Water>Let us assess>Q 5
Surface tension tends to minimise the surface area of a liquid. Suggest an experiment to prove this. (Follow the pattern: Required materials, procedure, expected observation).
MEDIUM
8th Kerala Board
IMPORTANT
Science for Class 8 - Part 2>Chapter 5 - Water>Let us assess>Q 6
Providing excess food for fish in an aquarium is a threat to its survival. Justify.
HARD
8th Kerala Board
IMPORTANT
Science for Class 8 - Part 2>Chapter 5 - Water>Let us assess>Q 7

Some substances when, dissolved in water cause, the hardness of the water.

Which of the following substances, cause hardness of water? 

Sodium chloride, calcium bicarbonate, calcium carbonate, calcium sulphate, magnesium sulphate, calcium chloride, magnesium carbonate.

HARD
8th Kerala Board
IMPORTANT
Science for Class 8 - Part 2>Chapter 5 - Water>Let us assess>Q 7

Some substances when, dissolved in water cause, the hardness of the water.

Sodium chloride, calcium bicarbonate, calcium carbonate, calcium sulphate, magnesium sulphate, calcium chloride, magnesium carbonate.

Is the hardness due to which of the above salts cannot be removed by boiling?

HARD
8th Kerala Board
IMPORTANT
Science for Class 8 - Part 2>Chapter 5 - Water>Extended activities>Q 1
What are the methods to be adopted for purifying polluted water for drinking purposes? Explain those you know.