EXPANSION AND CONTRACTION IN LIQUIDS
The experimental set up below can be used to demonstrate expansion of a liquid.

A glass flask is filled with coloured water and heated as shown above
OBSERVATION
Immediately the level of coloured water on the tube drops slightly at first and then starts rising.
EXPLANATION
The initial fall of the level of the water is due to the expansion of the glass flask which gets heated first. The water starts expanding when heat finally reaches it and it rises up the tube.
NOTE: The water expands faster than the glass.
QUESTION
Explain why there is a drop in the level of the water initially followed by a steady rise in the level of water.