September 5, 2003

On Sublimation: Science Lesson With Simon Delivers    So the Simon Delivers (online grocery store that delivers to your home) guy comes and in the containers with the frozen foods I find a package of dry ice. Little did I know that these packages are always there. What a treasure trove for homeschooling fun!

So I did a quick google search for fun science experiments with dry ice, donned some oven mits, and took the kids outside for an impromptu lesson on sublimation.

It was great. First I explained to our 4 and 2 year old the different states of matter (solid, liquid, gas, and plasma). I did this ever so briefly so that they might later remember "hearing something along these lines before" when we cover the subject in earnest in 2 or 3 more years. Then I showed them a solid piece of dry ice recovered from the Simon frozen foods container.

I tapped it on the picnic table to show them that it was solid and hard. I had them put their hands near it (though NOT TOUCHING it) to feel how cold it made the air around it. Then I took a spoon I had heated over the stove burner and laid it on the dry ice. As the intense cold of the dry ice interacted with the heat of the spoon, it caused the bowl of the spoon to vibrate very rapidly and produce a squeal. This is not unlike what happens with a tuning fork when you hit it against something to produce a tone. The harder I pressed the spoon against the dry ice, the louder the tone became and the pitch changed as well. It was great fun to lay the spoon against other objects (that couldn't melt) and not hear anything and then lay it against the solid carbon dioxide and hear it sing.

Next we put a small chunk of dry ice into a plastic film cannister for 35mm film and put the lid on. As the sublimation process progressed inside the cannister, the gasses built up and soon...BLAMMO, the top of the cannister popped off with a pleasing POP sound. I explained how the gas inside the cannister got so pressed together that it pushed the top off with a pop.

Then it was time for the dry ice in warm water trick. Each child had a mug of warm tap water and there was a pot of warm water on the middle of the table. I dropped a piece of the dry ice into each childs mug (again, with instructions to not touch) and they squealed with delight as the dry ice interacted with the water to produce "smoke" (really water vapor and carbon dioxide). It was fun to watch the water "boil" and smoke.

For the grand finale we dropped the remaining sizable chunks of dry ice into the center pot and WOZER, it was a witches cauldron of bubbling, smoking, roiling, fun. We even got the neighbors to raise their eyebrows at the spectacle. For a last minute fun, we added soap bubbles to the pot and watched as "smoke" filled suds bubbled way up high and spilled over the sides. Each child got to hold the suds (they're cold!). They especially enjoyed smashing the suds in their hands and watching the "smoke" come out of their hands (the trapped gasses inside the suds bubbles).

When the fun was over I explained again the states of matter and the word "SUBLIMATION" which means when a solid goes directly to a gas (instead of passing through the liquid state first). We didn't go into why sublimation works, or for what kinds of things it is for. But the kids now know a new science word and can repeat the definition and give an example of the process.

What great fun it was to do this impromptu science lesson in such a visually striking and memorable way. I think that one of the keys to successful schooling at home is to take the opportunities that present themselves and learning to spot them.

Don't let it sublimate away from you.


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