WHAT MAKES IT CHEMICAL?

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

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

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

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

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.

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.

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).

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

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.