AQA GCSE Doing work on gases

Doing work on gases

Doing work, means transferring energy. Energy is transferred from one energy store to another energy store by one of 4 ways :

1.Mechanically (using a force)

2.Electrically(Current)

3. Heating

4. Radiation

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When work is done to a gas energy is transferred by using a force, this means the energy is mechanically transferred.

When gases are compressed

In the gas syringe which is sealed on the right hand side, as the plunger is pushed inwards, work is done on the gas, so energy is transferred to the gas. This means that the internal energy store of the gas particles increases.

As the gas now has a higher internal energy, its temperature increases.

When gases expand

When a carbon dioxide fire extinguisher is used, as the gas leaves the extinguisher it expands.

As the gas expands, it does work to transfer energy to the thermal energy store of the surroundings, so the temperature of the gas will decrease.

Practice Questions

1. What does the term, doing work mean?

2. A bike tyre is inflated. During the inflation, the temperature of the tyre increases. Explain the increase in temperature.

3. A medical company invents a new freezing spray for warts. It uses compressed air which is sprayed onto the wart. As a result the wart is frozen and then falls off. Explain how this spray can freeze the wart.