Question

Observe the colour of vapour.
What change occurs in the colour of iodine vapours
in the lower gas jar?​

Answer 1

Explanation:

A gas jar containing air is placed upside down on a gas jar containing bromine vapours. It is observed after sometime, the gas jar containing air also becomes completely reddish brown.

Reason:

1. We observe that after some time, the red brown vapours of bromine spread  out into upper gas jar containing air. 

2. This mixing is due to Diffusion of Bromine vapour into air. Air from upper jar also diffuses into lower jar though we cannot see it. So, diffusion is the process in which mixing of substances with another substance takes place due to motion of particles.