A chemical change cannot always be seen unless that chemical change causes a physical change in which we see the end product. Some physical and chemical changes would be the digesting of food where you ingest the food, and then it goes through physical changes of being chewed. In turn, while in the digestive tract, it mixes with the acids, which causes chemical changes and makes it small enough to be absorbed for energy so the body can function.
When you boil water, this is a physical change only, but if you put an egg in the water and cook it to a hard boil, then there is a physical and chemical change. Because the egg becomes hard and you cannot revert it to its original form, it has gone through a chemical change.
In Physical Change, the material is only altered physically, but the molecular structure does not change whatsoever. Chemical change, on the other hand, alters the basic molecular structure of the material undergoing the change. A chemical change can actually also result in a physical change, while a physical change on its own alone cannot result in a chemical change.
Physical change is actually superficial, and it also has the possibility of being reversed, that is, physical change is reversible. A chemical change, on the other hand, is permanent and complete, and it is not in any way reversible. No new product or products is or are formed in a physical change, while there is always a new product formed in a chemical change. For a physical change, it is not followed by any change in heat, nor is there any energy change, while there is a great change in heat and energy for chemical change.