One of my goals with these science videos is to provide support to the homeschool community. After years of writing the Experiment of the Week, and presenting science shows for homeschool groups, I have been impressed with how strongly homeschool families are involved with hands-on science. I have also seen the need for a science curriculum that fulfills their educational needs. Starting with these videos, I hope to offer the homeschool community some of the science education support that they need, as well as a fun way to get students involved with scientific discovery.
I also try to use activities that involve common items. Most homeschoolers don't have access to test tubes, flasks, chemicals, microscopes and other scientific equipment. In the future, I hope to be able to guide them to inexpensive sources for science equipment to enrich their science curriculum.
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This experiment began as an interesting way to blow out a candle. Along the way, it developed into a way to blow wonderful smoke rings. No, this experiment does not require cigarettes. I don't smoke and never have. Instead of tobacco smoke, we will use candle smoke.
To try this, you will need:
- an empty plastic, 2 liter soft drink bottle
- a candle in a holder
- matches or a lighter
*WARNING* This experiment uses fire. Be safe, use common sense, and be sure there is an adult in the room, so you have someone to blame if something goes wrong.
Light the candle and place it on a table or flat surface. Hold the bottle about 3 feet away from the candle, with the opening pointed towards the flame. Give the side of the bottle a sharp tap. If your aim is good, you should be able to blow out the candle. With practice, you can do this from quite a distance.
How does that work? You are forming a vortex. A vortex is a mass of fluid that is moving is a whirling or rotary motion. The word fluid can be misleading, because we tend to think of a fluid as a liquid. To a scientist, a fluid is something the flows, so it can be a liquid or a gas. The rotary motion of a vortex can be a powerful thing. For example, a tornado is a vortex.
Another good example of a vortex is a smoke ring. As I played with the experiment, I was wishing for an easy, safe way to fill the bottle with smoke. As I succeeded in putting out the flame, I saw the answer right in front of me. There was a nice column of white smoke rising from the candle. I placed the bottle over the candle wick, letting the smoke rise into it. After lighting and blowing out the candle three times, I had a bottle full of smoke.
Once I had a bottle of smoke, I tried it again. I saw a dim puff of smoke shoot out of the bottle when I tapped it. That was fun, but it was hard to see. I found a dark background (the side of our microwave oven) and tried it again. I could see the smoke much better against the dark color. Next, instead of a sharp tap, a gave the bottle a gentle squeeze. Out popped a beautiful smoke ring. With some practice, I found it very easy to form a variety of smoke rings. By adjusting the amount of pressure, I could control the speed of the rings. That let me make a slow moving ring and then shoot a faster one through it. It also let me see things about smoke rings that usually happen too fast to see.
When you squeeze the bottle, you are forcing a "ball" of air out of the bottle. As this ball of air moves forward, the air on the outside encounters friction with the still air around it. That makes the surface of the "smoke ball" to move a little slower than the center. The center moves forward, pulling the slower, surface smoke in behind it. This forms a rotating ring. As this ring expands, the vortex keeps the mass of air together, turning it into the classic smoke ring. If you practice making slow moving rings, you can see this rotary motion.
I found that I could get quite a few smoke rings from a single filling with smoke. The rings work best if there are no breezes or air currents. The more gently you squeeze the bottle; the better the rings will be. I have played with other types of smoke ring generators, but this one gives you much more control for making close observations.
Have a wonder-filled week.
