A Science Experiment I Actually Liked

This is a science experiment I had to do yesterday in my marine biology class. We were learning about which types of water were thicker (or denser) than others. I thought it was just going to be a boring experiment, but I actually had fun doing it. I did this again today so I could take some pictures and show you how to do it.

What you need are simple things that can be found in most homes: two little jars about the same size, water, salt, index cards, and four colors of food coloring (red, blue, green, and yellow). You may need help.

Experiment 1:

For this first one, drops two or three drops of red dye in one jar, and two or three drops of blue dye in the other.

Fill the red jar (all the way to the top so no air can get in) with hot water and the blue jar with cold water, again all the way to the top.
Then place the index card over the red jar and flip it over on top the blue jar.
Slowly remove the index card from between the two jars. It's OK if a little water gets out.

Do you see a difference? Not really. This is because the cold water (blue jar) is on the bottom. Cold water is denser than hot water, making it hard for the red water to mix with the blue.

Experiment 2:

Rinse the jars out and do the same thing: hot red water and cold blue water. But this time, flip the blue cold water on top of the hot red.

Again, slowly remove the index card from between the two jars.
Everyone knows if you mix red and blue you get purple. But why did it happen this time and not last time? It's because the cold water was on top and it sank down to the hot, mixing the colors, and making purple!

Experiment 3:

Rinse the jars out again. Put a little bit of salt in one of them, along with two or three drops of green dye. In the other jar, add only yellow.

This time, fill both jars to the top with warm water.

Place an index card on the green jar and flip it over on the yellow.
Remove the index card and watch nothing happen to the green jar, while the yellow turns green. Why? Salt water is heavier than fresh and as a result, the salt water floats down to the fresh and changes the color.

Experiment 4:

Rinse the jars out again and do the same thing: salted green jar and yellow jar, both warm water. This time, the index card goes on the yellow jar and that one gets flipped over on the green.

Nothing happened. This is because salt water is thick and the fresh water cannot break through.

Science is one of my least favorite subjects in school, but I just thought this was such a cool and fun experiment. If you do this I hope you have as much fun as I did!