It is important to understand the differences between physical and chemical changes. Some changes are obvious, but others can seem tricky. It helps to think of physical changes as those involving changes that don’t change the make up of the substance, while chemical changes are those that create a new substance.

Physical Changes involve energy. The energy changes the substance, but the composition or make up of the substance does not change. For example, if you step on a soda can, you use energy to change the shape of the can, but the can is still made up of the same aluminum that it was to start with.

Physical changes include changes in state of matter. These are sometimes confusing, but remember – melted ice is the same water that started as frozen water in the ice cube. Steam given off when water is boiled is just water in its gas form.

Signs of a physical change:

If it ONLY changes –1. Size2. Shape3. State of matter

Chemical changes also involve energy, but in a chemical change, the result is a new substance that is chemically different from the original substance. The molecules in a chemical change experience a change in structure. Chemical bonds are broken and new arrangements in the molecules occur.

The substances produced in a chemical change has properties that are different from the original substance. Once a chemical change has occurred, it cannot easily be changed back to the original substance.

The most important thing to remember about chemical changes is that they result in the formation of a new substance.

Signs of a possible chemical change:

IF the substance -

1. Produces a gas (bubbles)2. Changes temperature3. Changes color4. Produces a precipitate (a

solid in a liquid)5. Gives off light 6. Gives off a new odor

Liquid