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

Color Fun - Experiment #25

"Is green really green?

You will need:
strip of paper towel
green felt-tipped pen or 1 drop of green food coloring
jar or glass with 1 inch of water

What to do: Make a spot of color about 2 inches from one end of the strip of paper towel. Hang the strip in the jar so the spot is above the water and the end of the strip is in the water. Let it stand for 15 to 20 minutes.

What happens: The green spot is gone but above the original spot, the paper has turned blue, and above that the paper is yellow.

Why: Most dyes and inks are combinations of coloring substances which can be taken apart by adding water or alcohol. Water moves up the paper the same way as sap rises in trees. As the water moves up, it dissolves the green spot and gradually moves the color up the strip of paper. But since the colors that make up green - blue and yellow - do not move at the same rate, they separate."


What happened when CKS tried it? I tried ink and food coloring. The food coloring was opposite from the ink because the blue is at the top, the green is in the middle, and only a little yellow at the bottom. And on the ink, there is a lot of yellow on the top and there is a little green in the middle, and some blue on the bottom. Ink worked better. Advice from CKS for when you try this at home: don't forget to label your paper towel strips.

CKS rating: 5 stars - Wow, better than TV!