Blow the Book Away - Experiment #76

"Move a book back and forth by blowing on it? Try it!

You will need:
Two long pieces of string or rope
Book
Wooden clothes hanger

What to do: Loop two pieces of string around the book and knot them. Then tie the loose ends of the strings to the rod of the wooden hanger so the book swings freely. Blow on the book. Continue blowing on it every time it swings back toward you.

What happens: Even gentle blowing seems to make the book swing vigorously.

Why: It is not only a question of force, but also one of timing. Although you may not be blowing very hard, regular blowing at the right moment sends the book flying." 

What happened when CKS tried it: It only works when you blow hard and fast. It was a little bit scary to use a big book because it might fall on the floor and make a big noise or land on your toes. When you try it, make sure to use a light, small book.

CKS rating: 3 stars - As good as an ice cream cone.

The Spreading Molecules - Experiment #314

"Do water molecules really move? If so, how fast and how slowly?

You will need:
2 clear glasses
cool and hot tap water
food coloring
medicine dropper

What to do: Fill one glass with cool tap water. Fill the other glass with hot tap water. Now, quickly place one drop of food coloring in each glass. (Make certain that all of the variables are the same. This means the glasses should have the same amount of water in them and that the same number of food coloring drops are added. Controlling variables is important to make the experiment scientifically correct.)

What happens: The food coloring spreads throughout the water in both glasses, but at different rates.

Why: The cold water eventually becomes completely colored because the water molecules are moving throughout the glass. But when the water is warmer (the hot tap water), the heat energy in it causes the water molecules to move much faster. This makes the food coloring spread out more rapidly. You might want to chart, or keep a record of, how much time it takes for the food coloring to spread evenly throughout each glass of water."

What happened when CKS tried it? We used boiling water and cold water from the fridge. The hot water spread first and the cold water spread last. It took the hot water 1 minute and 4 seconds, and the cold was 2 minutes and 33 seconds.

CKS rating: 3 stars - Good but not that good