We began the presentations in the “Work of Air” section of the Elementary Geography Album. This section begins with three experiments that were really fun and truly communicate the properties of air that it is essential to understand to be able to continue with the study of the work of air.
First, we wanted to establish that air takes up space. To do that, we used a glass bottle, a bit of clay, a funnel, and water. We attached the funnel to the bottle with clay. You have to make sure it is completely airtight. We didn’t manage this at first, but we kept trying until we achieved what we were attempting to show…
…that the water didn’t flow through the funnel, because the bottle was already full! You can see that there is already water in the bottle, from our previous failures. 🙂 But, the rest of the space is taken up with air!
We decided to try this experiment again with our chemistry equipment. We used an Erlenmeyer flask, a funnel, and a rubber stopper with a hole drilled in it. I later discovered that we have a tiny glass tube that is for attaching the funnel to the stopper, which would have made it easier. It still worked, through! You can see that the water, when poured all at once into the funnel, did not flow into the flask. It stayed in the funnel, because the flask was already full of air! (Sidenote: we bought all of our chemistry equipment at HomeScienceTools.com.)
We didn’t have any more time for experiments that day, so this next one was done a few days later. You could do it the same day if you have time and already have everything prepared.
This second experiment shows what happens when air is heated up. We used a knitting needle, a bit of playdough, the stub of a taper candle (about 6cm tall now), and a paper spiral. The spiral is balanced on the point of the knitting needle, and should reach halfway down the needle. Ours was a bit long, as you can see in the photo, and we had to cut it off a bit. The spiral should not touch the needle except on its point.
We lighted the candle and placed it below the spiral, and the spiral began to spin. We tried this first with a tealight candle, but it didn’t work because it didn’t heat up the air enough. It worked very, every well with our taper candle stub, however! It spun very fast! It clearly showed that the hot air rises, and the movement of that hot air rising is what makes the spiral spin. We moved the candle a few times to see what would happen, and noted that the spiral stopped spinning when it was taken away, and began again as soon as the candle was returned.
On to the next experiment! We did this one right after the second experiment. The purpose of this third experiment is to show a consequence of the rise of hot air: the formation of a vacuum. This seems like it would be difficult to demonstrate, but it turned out to be incredibly easy!
We used an oatmeal container and another taper candle stub for this experiment. You could also use a cardboard tube, but it has to be bigger than a paper towel roll. We turned the container upside down and cut out a little door. We also cut out a square in the bottom of the container (which is now at the top) to serve as a chimney. We put the candle stub under the container and lighted it. You need to let the candle heat up the air inside the container for two or three minutes before you can continue.
Meanwhile, we lit the other candle stub again. Now, you should note that the experiment calls for an incense stick here, not a candle stub. With an incense stick, you get smoke, which helps in the demonstration. But if you don’t have incense, and couldn’t find it at your local store (like us!), you can use a candle stub. It still shows the concept.
Now observe the candle flame (or incense smoke). You’ll note that no matter how you move the candle, the flame is always vertical. It’s very important that the children notice this.
Now move the candle slowly, horizontally, toward the door of the container. You’ll see that the flame is drawn inside the container. Move the candle away, and move it near again. Repeat several times so that children can see that it seems the other candle is sucking the flame inside the container. This happens because when hot air rises, it leaves a vacuum underneath it. And a vacuum attracts whatever is near to fill it up. This will be a very important concept to understand when studying the weather later.
And that’s it! The children now understand three fundamental concepts about air, and will be ready to continue their study of its work, including winds and weather!
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