1. WHAT MAKES IT CHEMICAL?

2. Review: Chemical Changes Chemical Properties
Mixtures and solutions are formed through physical changes compounds are formed through chemical changes
A compound is a combination of two or more substances that are chemically combined
Related to internal makeup of substances
Describe how a substance reacts with other substances to form new substances

3. Signs of a Chemical Change
1. A Color Change
A chemical reaction in trees causes the leave to change colors

4. Signs of a Chemical Change
2. Something Smells
When substance undergo a chemical change, often a new substance that smells different than the original substances is produced.
Ex. Rotting meat or sour milk

5. 3. The Presence of Bubbles or Frizzing
Signs of a Chemical Change
3. The Presence of Bubbles or Frizzing
The appearance of bubbles or fuzzing means that a gas is being produced
Ex. Vinegar and Baking Soda produce Carbon Dioxide

6. Signs of a Chemical Change
4. Light is Given Off
When a glow stick is bent, a capsule inside breaks, causing the chemicals within the capsule and the stick to react and give off light.

7. 5. A Change in Temperature
Signs of a Chemical Change
5. A Change in Temperature
Burning is a chemical reaction that releases heat energy
Photosynthesis is a chemical reaction that absorbs heat energy from the sun.

8. Signs of a Chemical Change
6. A Precipitate Forms
In some chemical changes, two liquids react and form a new liquid and a solid (precipitate).

9. Signs of a Chemical Change
7. It’s Permanent
A chemical change is very difficult or impossible to reverse.
Ex. Once you bake a change, you can never change the cake to batter

10. CAUTION
Although most of these signs indicate a chemical change, there are exceptions to the rule.
Boiling water produces water bubbles but this is a PHYSICAL change
Adding food coloring to water results in a color change, but it’s just a PHYSICAL change.