Which of the following is not a physical change?
Digestion of food
The digestion of food involves a long series of chemical changes. The complex substances we eat are changed into new simpler substances.
When candle wax melts, only physical state will change from solid to liquid.When the wax cools, it returns to its solid state.Breaking chalk into pieces and clay molded into a new shape both does not involve any chemical reaction,hence these changes are also physical changes.