Physical & Chemical Changes
Purpose: To introduce physical & chemical changes.
Background info: A physical change forms no new substance. It merely changes the shape, form, or state of a material. Examples: evaporating water, melting of ice, freezing of water, moving an object or others mentioned in your text.
A chemical change forms one or more new substances. Some familiar chemical changes: burning of gas, oil, coal, or paper; digestion, the souring of milk, the rusting of iron (more mentioned in your text). Chemical changes usually involve heat, burning, or some interaction with energy. Chemical changes are either endothermic (absorb heat energy) or exothermic (give off heat energy). A chemical change makes new compounds.
There are 5 ways to tell if a chemical reaction has occurred:
1. A change in color appears.
2. Gases are given off.
3. A new substance forms.
4. Heat is given off (exothermic).
5. Heat is required (endothermic).
Sometimes you can see only one of these, sometimes several.
Equipment: Bunsen burner, matches, goggles, marshmallow, skewer.
1. Tear a marshmallow in half.
2. Eat the marshmallow.
3. Follow the instructions for properly lighting a Bunsen burner. Then put another marshmallow on a skewer and hold it over the Bunsen burner until it is golden brown.
1. What type of change occurred in #1 above?_____________________
2. What type of change occurred in #2 above? ____________________
3. What type of change occurred in #3 above? ____________________
Circle YES if it is a chemical change and NO if it is not.
1. Water Evaporating YES NO
2. Log Burning YES NO
3. Mixing Sugar into Tea YES NO
4. A Car Rusting YES NO
5. Ice Melting YES NO
6. Boiling Away a Liquid YES NO
7. Milk Going Sour YES NO
8. Digesting Food in your Stomach YES NO
9. Making Sugar into Caramel YES NO
10. Roasting a Marshmallow YES NO
Explain the difference between a physical and a chemical change. Include some examples. (At least one paragraph)