Color Changing Liquids part 2

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!

Homeschool, Science/Math

Experiment: Make Your Own Thermometer

This experiment comes from last week’s Nonfiction Friday book: “Temperature: Heating Up and Cooling Down” by Darlene Stille. At the end of the book, you’ll find instructions for making your own thermometer out of simple household items. Since Cooper’s on a weather kick, we decided to give it a try.

(Note: In the spirit of total honesty, I have to say that this experiment didn’t work for us. I’ll offer a few ideas on that later; but, in the meantime, I encourage you to give it a try and see if it works for you.)

What you need:

  • Plastic water bottle (16.9 fl oz) with cap
  • Funnel (optional but makes life easier)
  • Liquid measuring cup
  • Rubbing alcohol
  • Water
  • Food coloring
  • Straw
  • Clay (something sticky to attach the straw to the side of the bottle)

What you do:

Place a funnel in the top of the plastic water bottle. Pour 1/4 cup of water into the water bottle. Pour 1/4 cup rubbing alcohol into the water bottle. Add a few drops of food coloring to the water/alcohol mix. Replace the cap and shake vigorously to mix. Remove the cap and insert the straw. Use the clay to hold the straw into place, ensuring the straw doesn’t touch the bottom of the bottle.

Here’s what’s supposed to happen: When you hold the “thermometer” in your hands, the alcohol/water gets warm and creeps higher in the straw, just like the mercury in an old-fashioned glass thermometer. This didn’t happen for us. I tried warming some water in a glass measuring cup and putting the bottle in it, the same way you’d warm a baby bottle. No luck. My tap water is very hard with lots of minerals dissolved in it. I am wondering if it would work with bottled or distilled water?

When you are done playing with your thermometer, make sure to dispose of the water/alcohol mix by pouring it down the drain or into the toilet. And make sure to dispose of the straw and water bottle where no little ones will get ahold of them.

Somebody let me know if you can get this one to work.