We recently tried an experiment from Steve Spangler Science, one of my favorite sites. You can find full instructions for the experiment….here, though we made a few modifications. Here’s our set up and what was supposed to happen:
The blue and green liquids (test tubes on the right in each stand) were mixed using cold water. The red and yellow liquids (test tubes on the left) were mixed using hot water. We put the blue (cold) water on top of the red (hot) water. We put the yellow (hot) water on top of the green (cold) water. We expected the heat to rise and cold to sink in each situation. So, we expected the cold blue to sink into the hot red and create purple. We expected the hot yellow to be perfectly content on top of the cold green, therefore not mixing at all. This is indeed what the beautiful video on Spangler’s site showed.
However, we learned a thing or two about how precise one has to be with science experiments. Here was our result:
Whoops! This wasn’t what was supposed to happen. The yellow-green at left wasn’t supposed to mix together. However, I had used an old recipe card to separate the two test tubes, before I placed them one on top of each other. Pulling out the recipe card wasn’t easy, and I think I ended up lifting up the top test tube, introducing some air and force that caused the two liquids to mix. Spangler had opted for a waxy playing card, which I’m sure slipped more easily. So, we talked about how careful scientists need to be with their experiments to produce accurate results.
Seriously, if you try this at home, follow Steve Spangler’s lead and use something slippery (a playing card) to separate the two liquids. It will pull out from between the test tubes much more easily. Oh, and this is very messy, so we recommend putting a cookie sheet underneath your workspace. We always have fun with these experiments even when we aren’t successful!