Page 60 - ScienceStd4

Figure 4. For example, the vapour coming from the spout of a
kettle with boiling water is warm and in a gaseous state. When
this gas comes into contact with a cooler object like glass or
mirror, it condenses and appears as mist. This mist continues
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to cool and turns into a liquid state. This demonstrates that
when gas is cooled, it changes into a liquid. The process is
called condensation. Therefore, condensation is the process of
changing gas to liquid state.

Exercise 1

1. What is matter?

2. Give two examples of each state of matter and explain
their uses in our daily lives.

3. Based on shape and volume, how does a solid state differ
from a liquid state and a gas state?

4. How does water exist in three states of matter?

Freezing point of water

Water freezes when it reaches a specific temperature. The
freezing point of water is the exact temperature at which a liquid

(water) freezes and changes into a solid (ice). Ice has many
uses, such as preserving food and beverages. The coldness
helps slow bacterial growth and prevent spoilage of foods.

Experiment 5: Investigating the freezing point of water

Aim: To demonstrate the freezing point of water

Materials: Refrigerator, table, thermometer, water, and
a plastic cup

Note: Do not remove the thermometer from the

water while reading the temperature.

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