Physical changes are changes affecting the form of a chemical substance, but not it's the chemical composition. Physical changes are used to separate mixtures into their component compounds, but cannot usually be used to separate compounds into chemical elements or simpler compounds. Physical changes only change the appearance of a substance, not it's the chemical composition.
Chemical changes cause a substance to change into an entire substance with a new chemical formula. Chemical changes are also known as chemical reactions. A chemical change is a permanent change. A Physical change affects only physical properties, i.e. shape, size, etc. Some examples of physical change are freezing of water, melting of wax, boiling of water, etc. A few examples of chemical change are digestion of food, burning of coal, rusting, etc.