Page 93 - Innovator's Science-8

What do you observe?

As you do this, you will notice that the volume of air inside the syringe
decreases. What can we say about the behaviour of gas in the syringe?
When you compress the air by pushing the plunger, the particles are forced
to come closer. This shows that the gas particles have a lot of space

between them in their natural state, and this space can be reduced by
applying external pressure. If you stop pushing the plunger, the gas
particles spread, and the plunger moves back to its original position.

Repeat this activity using water and observe. You would observe that water
is practically incompressible. Let us perform another activity to learn about
the interparticle spaces in liquids.

Activity-2 • Fill a glass vessel halfway with water and label the water level as Point A.
Experiential Learning • Add two teaspoons of sugar into it.
• Mark the new water level on the glass vessel B.
• S r the water with a glass rod to dissolve the sugar.

• Evaluate whether the water level will increase or decrease with respect to the
mark B.
• Mark this water level again as C.

Sugar
particle

Water
particle

Magnified schematic
picture of distribution of sugar Variation in water levels
particles in water

When sugar is added to water, you may notice that the water level first rises
because the sugar takes up space. But after the sugar dissolves, sometimes
the water level decreases slightly. This happens because the sugar particles
fit into the tiny empty spaces between the water particles. Since sugar

particles occupy these spaces, the total volume of the solution becomes less
than the sum of the separate volumes of sugar and water. This shows that
there is some space between water particles that the sugar particles can fill.
Other substances like salt or glucose dissolve similarly, while insoluble solids

like sand or small stones do not dissolve and remain separate.

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Science-8