Physical change

In science it is important to be able to identify the difference between a physical change and a chemical change.

A physical change is when:

1. There is a change in state or shape but there is no chemical change. The chemical formula remains the same. 
2. You can also reverse the change.

When water changes to either ice or steam it has undergone a physical change. It is still H2O in all three states. We could also change the ice or steam back into water. Here is a video of what happens when H20 changes into the different states.

Other examples of physical change include heating gas, bending metal, or melting plastic. They change their state or shape but nothing changes at the atom or molecule level.

We did the mentos and coke experiment and discussed how it undergoes a physical change (it is often mistaken for a chemical change). The mentos actually just speeds up the release of the carbon dioxide because its bumpy surface makes it easy for the dissolved CO2 to form as bubbles. We could, in theory, gather the released CO2 and the spilt coke, put it back together again and get our fizzy coke back.