Germination of seed is a chemical change because the original seed can never be re-gained back from the plant it grows into.The germination of a seed is a complicated process that involves many chemical reactions as well as changes in the physical appearance of the growing plant. Clearly, the process is too complicated to say that it is merely one or the other.
It begins with water. Water soaks through the outer layers of the seed and combines with an enzyme inside the seed to start the reactions that result in the growth of the embryo.
Again there are both physical and chemical changes that occur, but primarily the changes are chemical.