Homeschool Science: The Physics of Temperature and a Homemade Working Thermometer

We weren't meant to spend more than maybe a month, tops, on this meteorology unit. What we really want to be studying is astronomy, and we'll have to get to it soon if I want to have us set up to watch the total solar eclipse as our culminating activity, but meteorology has never been something that's interested the kids enough to study before, and so we just need to zip through it just so the kids have some basic background information, and some context for relevant bits of knowledge.

There will be no weird gaps in our homeschool curriculum!

This unit is kind of taking forever, though. Like most of our studies, it's heavy with hands-on activities, but since they're hands-on weather activities, they keep either requiring specific conditions outside that we have to wait on (can't identify clouds if there aren't any!) or take days and days to complete (this week, the kids are working every day on a temperature-gathering experiment, and it's a huge pain in the butt).

Even this particular lesson was kind of a pain in the butt, because we had to put it off when we discovered that the little kid had used up all of our clear straws on a huge, messy (though delicious) milkshake project. We finally got it done this week, though, and happily, it was so awesome that it was worth the wait!

In order to understand how a thermometer works, you have to understand the physics of temperature. This Crash Course Physics video gets too hard for the little kid less than halfway through--



--but does contain plenty of reinforcement of the main takeaway, that heating expands solids, liquids, and gasses, and cooling contracts them. The rate and intensity depend on the substance, but if you know that rate and intensity of a particular substance, you can use its expansion and contraction to then measure the temperature around it.

And boom! You have a thermometer!

We studied how to physically use a thermometer as a measuring tool in a previous lesson (I probably should have told you about that lesson first, but bizarrely, I chose not to. I'll tell you about it later, I guess!), and the difference between the various scales of temperature measurement. So when we finally scored some clear straws (at the movie theater, in partial recompense for the ridiculously high ticket prices for Guardians of the Galaxy 2), the kids were all set to make a working thermometer for themselves, using sugru, a Starbucks Frappuccino bottle (I bought some different types of coffee drinks to test out for an upcoming camping trip, and this one was NOT a winner--it tasted weirdly chemically and...oily, kind of?) and this tutorial:

The kids were able to follow the tutorial independently, although I'd advise you to let the thermometer rest for a couple of hours before you use the eye dropper to add a couple of inches of water to the straw. Our rubbing alcohol was already at room temperature, but the water that the kids got from the sink must have been cold, because just by sitting on the counter the thermometer soon maxed out its temperature reading, with the colored liquid all the way at the top of the straw and dripping down.

But yes, after you fix that the thermometer works just as you'd like it to, and you can move it inside and out, around to different parts of the house, put it in the refrigerator and then take it out later and watch the water level rise while you're eating dinner, etc. 

P.S. If that Physics of Temperature video wasn't too hard for you, you should also check out this second video on the subject, and then this video on thermodynamics. If we were going in a different direction with our study of heat, the kids would have LOVED to spend some time burning and melting stuff to determine melting and boiling points, etc., but I'll save that fun activity for another time.

P.P.S. Want to follow along with my craft projects, books I'm reading, road trips to weird old cemeteries, looming mid-life crisis, and other various adventures on the daily? Find me on my Craft Knife Facebook page!