1. Topic 2 – Changes in Matter

2. Types of Changes Matter can change in one of two ways.
Physical change – This is a change in which no new substance is produced. Eg. Melting, freezing, dissolving, breaking things, etc… These changes are “usually” easy to reverse.

3. Chemical Changes. This is a change when one or more new substances are produced. Eg cooking, rusting, burning, etc… The new substances have properties that are very different from the original materials. (Compare a pile of ashes with the pile of wood that it came from)

4. Indicators of a Chemical Change
Heat is produced or absorbed. (it gets hotter or colder)
A new substance is produced. (burning always produces water vapour and carbon dioxide.
There may be an unusual change in color.
A gas is produced. (May be bubbles)

5. 5. A precipitate may form. (a semi-solid substance in the bottom of a liquid)
The change is difficult to reverse
The starting materials are used up.
Not all of these indicators has to be present but usually, several are.