Question

How will you demonstrate the thermal expansion in a liquid? Describe an experiment.

Answer 1

• Take a round bottomed flask and fill it with coloured water up to the brim.
• Close the flask with a single-holed rubber stopper.
• Insert a capillary tube into the flask such that some water from the flask gets into the capillary tube and reaches a certain level.
• Heat the flask over a burner.
• Observe the level of water in the capillary tube.
• As the flask is heated, the water expands, and the level of water in the capillary tube rises.
• This is due to the thermal expansion of water.

Now stop heating the flask and observe the level of water in the capillary tube. The level of water goes down as the temperature of the water in the flask decreases. Liquids expand on heating, and contract on cooling. Thus, liquids expand on heating and contract on cooling.