Page 68 - Viva ICSE Science 5 : E-book

Gas

The molecules in gases are very loosely packed as compared to
solids and liquids. There is almost negligible force of attraction
between the molecules, so they move freely in all directions.

Because of this reason, gases have the following properties.
(i) Gases do not have any shape. We cannot even see them.

(ii) They do not have a fi xed volume.
Arrangement of
(iii) They have weight.
molecules in gases
(iv) They can move freely in any direction and occupy any space
available to them.
Negligible
Our atmosphere is also made up of diff erent gases like
nitrogen, oxygen and carbon dioxide. Oxygen and carbon It refers to the quantities,
so small that they can be
dioxide are two important gases necessary for the survival of
ignored or neglected.
life on the earth.

ACTIVITY TIME

To show that gas occupies space
You Need:
A glass, a bucket, water

What to Do:
• Take the bucket and fi ll it with water.

• Now hold the glass upside-down and push it straight into the
bucket, do not tilt the glass.
• Observe whether water enters into the glass.
• Now tilt the glass a little and observe again.

You will observe that water does not enter the glass when it is pushed
straight into the water. But when the glass is tilted, bubbles come out
from it and water fi lls into the space under it. This proves that gas
occupies space.

Solubility of Substances in Water

Solubility of a substance is its property to dissolve in some other substance to form a
mixture of uniform nature. The substance which gets dissolved is called solute, while
the other substance in which the solute gets dissolved is called solvent. The resulting

uniform mixture is called solution.

54