Look at the diagr

(a) when the glass plate is pulled away between the two jars, the brown gas from jar A mix up with colourless gas in jar B. Red-brown gas is seen to slowly diffuse through the colourless gas in jar B. After sometime, Jar B becomes completely red brown in colour.

(b) The mixing of two gases in the above experiment is called Diffusion.

(c) The brown gas present in jar A could be Bromine vapours.

(d) The colourless gas in jar B could be air.

(e) Potassium permanganate (coloured solid) and Water (colourless liquid).