The changes that can be observed and specified like changes in color, hardness, rigidity, density, fluidity, melting point, boiling point, etc. are the physical changes.
Chemical Changes
A chemical change is a change that results in the formation of new chemical substances.
It involves the making or breaking bonds between atoms.
Burning of coal
The burning of coal is not a physical change.
When coal is burnt, the carbon is changed to Carbon dioxide(formation of the new products).