Is formation of acid rain an physical change?

Mainly it's chemical.

In an acid rain it's sulfuric acid that pours on earth. The formation of it has this procedure.

• Mainly due to the industrial activities ##SO_2## gas is released to the air.
• ##SO_2## reacts with ##H_2O## (water) molecules in the clouds. ##color(blue)(SO_2)+color(blue)(H_2O)->color(blue)(H_2SO_4)## (This is no balanced reaction.)

There are many other gases that cause acid rains. Here is a link to read more.