Chemical Change: New Substance Forms

A chemical change is when a new substance forms. A chemical change has happened when there is a change in colour, when gas is smelt or when seeing bubbles, seeing a new solid, or when observing that energy is produced or absorbed in the form of heat and light. An example of a chemical change is when bread is turned into toast. This is a chemical change because the process cannot be reversed, so toast cannot be turned back into bread.
A physical change is when no new substances are formed. In a physical change, there may be a change in shape or, expansion and contraction occurring. An example of a physical change is when water freezes into ice. This is a physical change because the process can be reversed, so ice can be melted to form water