Explain the difference between a physical change in property and a chemical change in property

Difference between a Physical change and a Chemical change in property:

Physical change of a property is basically the change that is visible from outside like colour texture etc. But in chemical changes the chemical identity gets changed.  

For example if we melt an iron bar then the state of the bar will be changed from solid to liquid but in both the state the metal is iron. So this is a physical change.  But if we burn a piece of wood it will turn into ashes where the internal chemicals of the paper will be changed and turned into carbon.

what was the answer?

at positions a, g kinetic energy is maximum.

at position d, potential energy is maximum.