Describe an experiment to show that a gas expands on being heated and contracts on cooling.

• Take an empty flask and clamp the flask in an upside-down position over a beaker of water in such a way that the glass tube dips inside the beaker.
• Now heat the flask at the top.
• The air in the flask expands and moves out of the flask through the tube into the beaker containing water.
• Observe the bubbles of air inthe water.
• Now allow the beaker to cool.
• As the air inside the flask contracts, the water rises up the tube.
• This proves that gas like air expands on heating and contracts on cooling.