Question

describe an experiment to illustrate thermal expansion in gases ?

Answer 1

The following experiment shows that gases expand when they experience heat i.e. thermal expansion of gases :
REQUIREMENTS : A balloon , liquid nitrogen or dry ice , container

PROCEDURE : Fill the balloon with air partially . Place it over liquid nitrogen taken in a container .Note the change in the size of the balloon.Now take it out from liquid nitrogen.Again a change in the size of the balloon is noted.Dry ice can also be used instead of liquid nitrogen.

OBSERVATION : The size of the balloon reduces when it is subjected to liquid nitrogen. When it is taken out , it regains its original size i.e. it expands.

THEORY : The temperature of dry ice or liquid nitrogen is much lower than the room temperature. As the balloon is dipped in liquid nitrogen , the temperature of the gases inside the balloon decreases and their volume decrease.This decrease in volume of gases leads to reduction in the size of balloon.
When the balloon is taken out of the liquid nitrogen , the gases inside the balloon experience a much higher temperature i.e. the room temperature.This increase in temperature leads to expansion in the volume of gases inside the balloon. As a result, the size of the balloon increases and the balloon regains its original shape.