Page 17 - Understanding NCERT Science 09

Q uestions = mass/volume). 1.4.1 EFFECT OF CHANGE OF TEMPERATURE

1. The mass per unit volume of a
Activity _____________1.12
substance is called density.
(density
Take about 150 g of ice in a beaker and
•
suspend a laboratory thermometer so
Arrange the following in order of
increasing density – air, exhaust
as in Fig. 1.6.
from chimneys, honey, water, that its bulb is in contact with the ice,
chalk, cotton and iron.
2. (a) Tabulate the differences in
the characterisitcs of states
of matter.
(b) Comment upon the following:
rigidity, compressibility,
fluidity, filling a gas
container, shape, kinetic
energy and density.
3. Give reasons
(a) A gas fills completely the
vessel in which it is kept.
(b) A gas exerts pressure on the
walls of the container.
(c) A wooden table should be
called a solid.
(d) We can easily move our hand
(a)
in air but to do the same
through a solid block of wood
we need a karate expert.
4. Liquids generally have lower
density as compared to solids.
But you must have observed that
ice floats on water. Find out why.

1.4 Can Matter Change its State?

We all know from our observation that water
can exist in three states of matter–
• solid, as ice,
• liquid, as the familiar water, and
• gas, as water vapour.
What happens inside the matter during
this change of state? What happens to the
(b)
particles of matter during the change of
states? How does this change of state take
place? We need answers to these questions, Fig. 1.6: (a) Conversion of ice to water, (b) conversion
isn’t it? of water to water vapour

6 SCIENCE

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