Page 58 - ICSE Chemistry 6

Solids

• Solids have a defi nite shape, mass and volume. The molecules are
ghtly packed in solids and cannot be moved. Solids like rock and
table do not change shape. However, some solids like rubber can
change their shape when an external force is applied to them.
Once the force is removed, rubber returns to its original shape.
• Solids are incompressible. In solids molecules are closely packed
together and the intermolecular forces are the strongest.
Therefore, solids are fi rm, compact and almost incompressible. Fig. 3.2: Arrangement of molecules
in a solid
The molecules in solids only vibrate about their respec ve fi xed
posi ons.

• Solids have high density. Density of a substance is the amount of ma er contained per unit volume.
Since the par cles in solids are closely packed, they possess high density.
• Solids do not diff use. Diff usion refers to the intermingling of par cles of diff erent substances on
their own. Solids have strong forces of a rac on and so the molecules do not move away from
each other. Therefore, solids do not diff use.
Let’s perform the following ac vi es to observe that solids have defi nite shape and volume.

Activity 3.7

Aim: To observe that solids have a defi nite shape

Materials required: A key ring, a notebook, some other solid objects
Procedure

• Collect objects like notebook, pen, pencil, stone, wooden scale and key ring.
• Keep these objects on a table.
• Observe these objects carefully for 15–20 minutes.

Observa on: You will observe that there is no change in the shape of these objects.

Conclusion: This shows that solids have a defi nite shape.

Activity 3.8

Aim: To observe that solids have a defi nite volume

Materials required: A small bowl, 2 large bowls, a tumbler, a thread, a paperweight
Procedure 1
• Take a glass bowl and a glass tumbler, and fi ll them with equal quan ty of water.

• Place both of them in bigger bowls.
• Take a paper weight and e it with a long thread.

• First suspend the paper weight into the glass bowl.

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