Lab #1 Experimenting with States of Matter
When you mixed the cornstarch and water a thixotropic mixture was formed. It is a mixture that cannot consistently retain the properties of any one state of matter. Thus, the mixture that was formed was neither a liquid or a solid.
Lab #2 Experimenting with Physical Changes
Your cup should contain only salt. The water evaporated and since a new substance was not formed--a physical change has taken place.
Lab #3 Experimenting with Chemical Changes
You should have observed the popcorn kernels rising and sinking during the five minutes. The vinegar and baking soda combined to form a gas. This was shown by the bubbles that appeared on the kernels. When the kernels reached the surface of the liquid the bubbles popped, causing the kernel to fall to the bottom again. Thus, a chemical change has occurred because gas was given off.
Lab #4 Experimenting with Chemical Changes 2
After approximately 20 minutes, you should see rust forming at the sides of the cup where the steel wool was touching. Since you know rusting is a process that cannot be reversed, you know a chemical change has taken place.
For more fun, at home experiments check the links on the next page.