Mg₃N₂ + 6H₂O = 3Mg(OH)₂ + 2NH₃
Physical changes occur when objects or substances undergo a change that does not change their chemical composition. This contrasts with the concept of chemical change in which the composition of a substance changes or one or more substances combine or break up to form new substances.
Greater rainfall has an greater increase on the rate of chemical weathering. Rain is a form of precipitation.