LIWA

Water

ICSE Class 6 · Chemistry · Chapter 7

What this chapter covers

Key definitions

Irrigation is the supply of water to crops in the fields by canals, pipes, sprinklers or other means.

Fresh water is water that has very little salt dissolved in it, such as the water of rivers, lakes, ponds and wells.

Groundwater is the water that collects under the surface of the ground in the spaces between soil and rocks.

Water is called a universal solvent because it can dissolve a very large number of substances.

A soluble substance is a substance that dissolves in a liquid, like sugar in water.

An insoluble substance is a substance that does not dissolve in a liquid, like sand in water.

A solute is the substance that dissolves in a liquid.

A solvent is the liquid in which the solute dissolves.

A solution is the mixture that forms when a solute dissolves completely in a solvent.

A homogeneous mixture is a mixture that has the same composition all through, so its parts cannot be seen separately.

Water scarcity is a shortage of clean fresh water to meet the needs of the people in a place.

Water pollution is the making of water dirty and harmful by adding unwanted substances to it.

Key points

Questions answered

Name three ways in which water is used at home.
Drinking, cooking and bathing. (Washing clothes, cleaning and flushing toilets are also correct.)
Give one use of water in industry and one in agriculture.
Industry: cooling machines or making paper. Agriculture: irrigating crops such as rice.
Name four sources of fresh water.
Rivers, lakes, ponds and wells (hand pumps and tube wells also draw water from under the ground).
Some copper sulphate is dissolved in water. Name the solute, the solvent and the solution.
Copper sulphate is the solute, water is the solvent and the clear blue liquid is the solution.
Why is a solution called a homogeneous mixture?
Its composition is the same all through, so the solute cannot be seen separately and every part looks and tastes the same.
Why is water called a universal solvent?
Water can dissolve a very large number of substances.
State three reasons for water pollution.
Untreated sewage, harmful waste from factories, and fertilisers and pesticides washed from farms. (Garbage and plastic thrown into water is also correct.)
What is rainwater harvesting, and how does it help?
Rainwater harvesting is the collecting and storing of rainwater for later use or to send it into the ground. It saves water and raises the level of groundwater.