The first of four school-age science programs was a success! It started out a bit slow, but by the end, the kids were entranced. Dry ice crystal balls will do that.
I broke the program up into two main sections: education and experiments. The kids would rather have jumped straight into the experiments, but I wanted them to have some knowledge about what was happening.
I pulled a lot of the information from the matter section of Chem4Kids.
Notes to self: next time do more prepwork so as much of the individual experiments are ready to go, such as putting corn starch in the bowls, or pouring the raw ingredients for ice cream into the baggies.
I opened by asking what matter is (everything around you; anything that takes up space), and asked who knew what the three states of matter are (technically there are five, but I didn’t want to go into plasma and BCEs, in large part because they’re a mystery to me). We talked about the characteristics of solids, liquids, and gases, and how they change states. I used examples of sitting down (solid), walking (liquid), and running (gas) to show how much energy is used in different states. I gave the children a blank graph to fill in showing how molecules arrange themselves in the various states.
When they finished the pictures, I talked about what the changes in states of matter are called and put up a handy-dandy chart so the relationships could be seen:
- Solid –> Liquid = Melting
- Liquid –> Solid = Freezing
- Liquid –> Gas = Boiling/Vaporization
- Gas –> Liquid = Condensation
- Solid –> Gas = Sublimation (think the smoke rising off dry ice)
- Gas –> Solid = Deposition (frost forming on windows or snowflakes)
- States of water
- Freezer bag ice cream
- Dry ice crystal ball
States of Water
Purpose: To show vaporization and condensation.
This was a simple one. I had baggies filled with ice, water, and gas/empty. The water went into a pot on a hot plate (I should have used ice, but in the name of saving time, I didn’t). I put a lid on the pot and left it alone for a few minutes until there was enough steam to condense on the underside of the lid. At that point, I walked around with the lid to show the water droplets.
Purpose: Is it a solid or a liquid? (It’s a colloid!)
The basics for oobleck is one part water to one-to-two parts corn starch. Food coloring can be added if you’re so inclined. Each child had a bowl with the ingredients in it, and had to mix it with their fingers. Oobleck is fun in that it acts like a solid if you put pressure on it, but like a liquid if you move it slowly. You can feel it shifting when you hold it, and it’s a weird sensation.
While the children were playing with the oobleck, I explained what colloids are (a solid suspended in a liquid, but the particles are small enough to make it appear homogeneous). Examples of colloids would be Jell-O and milk.
Freezer Bag Ice Cream
Purpose: Liquid to Solid.
This experiment was a mixed bag (ha ha). It was split fairly evenly for who had actual ice cream and who ended up with a milk shake. There are many recipes out there, so a quick search will overwhelm you with results. I used one that called for a 1/2 cup of milk versus 1 cup (I figured it would harden faster).
Make sure to have something to wrap the baggies in – towels, newspapers, etc… – as the baggies get very cold. Also make sure to have extras of both quart and gallon baggies since there will be some breakage and you might have to double/triple bag it.
Dry Ice Crystal Ball
Purpose: Sublimation and because it looked cool.
This is an awesome, crowd-pleasing experiment, and if you have a source of dry ice nearby, I highly recommend it. The gist of the experiment is trapping the smoke in a film of bubble stuff that has been wiped across the top of a bowl. The children LOVED IT! I ended up using a bunch of plastic cups in addition to the bowl I brought so each table could have their own crystal ball to play with.
In a large-ish bowl (mine was 12″ across), or a much of smaller cups for individual tables/children, fill about halfway with water. Drop some dry ice pellets in.
In a small bowl, pour a little bit of water and a whole lot of dish soap. Take a strip of fabric and immerse it in the solution. Make sure the fabric is longer than the dry ice/water bowl is wide. Once it is soaked, take it out, hold it taut and wipe it across the rim of the bowl (make sure the rim is wet). You should be able to see the bubble film form as you pull the fabric across the rim.