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My son and I are testing the hydrogen gas. Nice to end with a bang! |
Today I did a demonstration show for my son’s third grade
class. The kids are studying the states
of matter in school. I asked him if he
would like me to come in and do some demos for his class about this interesting
topic. He was very excited about the
idea, so I set it up with his teacher and here we go.
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Water and Ice Balloons |
The first thing I did was pass around three balloons; one
was filled with air, another was filled with water, and the third was filled
with ice. If you ever want a fun party
favor for kids, just throw some water balloons in the freezer. They were absolutely thrilled by the frozen
balloon. I described to the kids how I
made it so they could repeat the experiment at home. The three balloons provided a nice platform
for comparing and contrasting the properties of the three states of matter.
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Siphoning the blue water. |
Next I turned my attention a common property of liquids and
gases: they both flow. It’s easy to see how liquids flow and take on
the shape of their container, but not as easy to see gases do this. First I set up a siphon with some blue water
to show the kids that water will flow through a tube to the lowest point. Then I generated some carbon dioxide gas in the
same container and tried to siphon it. I
did this demo successfully with my classes about a month ago, so I was
confident that I could repeat it here today.
Although we confirmed the presence of carbon dioxide in the source
container with a candle, I did not wait long enough for the gas to flow through
the tube into the lower container. I
guess the high-energy third graders got the best of me on this one.
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Making carbon dioxide |
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Pour the gas. |
The next thing I did was another demo with carbon dioxide
gas. I filled a small fish tank with the
gas by dumping a large amount of baking soda in the bottom and then pouring
vinegar on top of it. The kids loved
watching the bubbling reaction. Many
kids asked what would happen if I added food coloring to the mixture, so I
dropped in some green food coloring. I
think they were disappointed that the bubbles weren’t green. I tested the carbon dioxide with the candle
again to show the kids how much gas we had made. Then I blew soap bubbles into the tank. This demo is always a big hit because the
soap bubbles hover on the top of the carbon dioxide. I’m used to doing this for teenagers, who are
mildly amused by the whole thing. But I
didn’t think about how excited kids get when they see soap bubbles. The front row jumped up and started chasing
the bubbles and popping them before they went into the tank. Once I convinced them to let the balloons go
into the tank, we got to see the effect.
But, honestly, I think they were more interested in the ones that missed
the tank!
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Making more carbon dioxide. |
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The floating bubble trick. |
The finale was the electrolysis of water demo. I wanted to show the kids a chemical reaction
that would demonstrate the chemical formula of water. Once I got the Hoffman appartus set up and
going, I let them come up in small groups to look at the reaction going. I’m not sure that the kids could make the
connection between the two to one ration of hydrogen and oxygen gas to the
water molecule. However, I think they
all enjoyed seeing the reaction and observing the color changes. They also got to see the water displacement
technique as we trapped the gases at the top of the tubes. I finished off the day with the pop of the
hydrogen gas. Overall, it was a lot of
fun to work with the kids. I hope that they
learned something from my show, but I’m sure that they walked away thinking
that science experiments are fun to do.
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Here I'm trying to get the third graders to understand that water is 2 parts hydrogen and one part water. They were mostly interested in the colors, the bubbles, and the water displacement. I'm okay with that. |
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