Question

what is a physical and a chemical change

Answer 1

Chemical change:_
a usually irreversible chemical reaction involving the rearrangement of the atoms of one or more substances and a change in their chemical properties or composition, resulting in the formation of at least one new substance: The formation of rust on iron is a chemical change.
Physical change:_
Physical changes are changes affecting the form of a chemical substance, but not its chemical composition. Physical changes are used to separate mixtures into their component compounds, but can not usually be used to separate compounds into chemical elements or simpler compounds.

Answer 2

A physical change in a substance doesn't change what the substance is in a chemical change where there is a chemical reaction a new substance is formed and energy is either given off or absorbed.