Is crumpling a sheet of paper a physical or chemical change? Why?

It's a physical change. You're not changing the chemical make up of the piece of paper. Only the appearance.

I believe it is a physical change. Crumpling a sheet of paper does not change any properties of the paper and it does not form a new substance it must be a physical change. It is only the shape or form of the paper that is being changed. Hope this answers the question.