The kids and I had a week of science experiments. I love seeing the look on their faces when we do experiments. The experiments we did are inexpensive and provide hours of entertainment and investigation for the kids. And it was something the whole family got interested in.
The first one was a homemade lava lamp. Find a plastic bottle. Fill it a little under half full with water. Then add an equal amount of oil. (I used canola oil, but any oil will work.) Wait for the oil and water to separate.
Then add 6-10 drops of food coloring. Watch as the food coloring sits at the edge of the oil and water boundary. It will eventually break free from the oil and create a really cool design in the water.
After all the food coloring droplets have broken free from the oil, drop an effervescent tablet (cheap Alka-Seltzer) in the jar. We broke each tablet into four pieces before dropping it. When the bubbles stop, add more tablets. When the boys decided to drop about 4 tablets in at a time, the bubbling was so extreme you couldn't see the oil/water boundary anymore.
This was a great lesson in density for the kids!