Everything Kids' Magical Science Experiments Book (7 page)

It looks like the candle magically went out!You didn't blow on it, and in fact, it looks like nothing happened to it—it just went out on its own. But there's a science secret behind what's happening here. You see, when baking soda comes into contact with vinegar, a chemical reaction occurs. That's what causes the bubbles and foam you see. This reaction produces carbon dioxide, a gas you can't see or smell and the same gas you find in the bubbles in a can of soda. Carbon dioxide is heavier than air, which means it tends to fall down through the air toward the ground. What you did by “pouring” the large glass into the glass containing the candle was allow the carbon dioxide to escape from the reaction taking place in the large glass. It fell into the smaller glass, surrounded the candle, and caused it to go out.

What's great about this experiment is that it is so easy to do over again. Go ahead and try it again! You might need to clean out the large glass and start with fresh vinegar, but each time you do, the results should be the same.

However, there is another way to blow out a candle without blowing directly on it. To do this, you need to place the lit candle flat on the table, and place a cylindrical object (such as a can of soda or a can of frozen juice concentrate) directly in front of the candle. All you need to do is blow toward the can—the candle behind it should go out. How is this possible? The air isn't blocked by the can. Instead it splits, passes around it on either side, meets up again on the back side, and blows out the candle. Try this with different candles, and objects of different shapes in front. Why does a cylinder seem to be the shape for blowing out the hiding candle?

Question: Can you make a seesaw out of a candle?

KIDS' LAB LESSONS

Most people, when asked to imagine a seesaw, conjure up images of a playground with children sitting on either end of a large toy, bounding up and down, squealing with joy. For most people, and perhaps for you, this is their only experience with a seesaw. But in this experiment, you will be building your own seesaw, one that needs no outside help to keep rocking back and forth, can fit on your kitchen table, and is definitely not something children should be riding.

When a candle burns, it loses some of its wax, which melts and sometimes drips over the side. This can produce a big mess if it goes unnoticed, but in this case, that dripping is exactly what you want to see happen. You'll have to trim the bottom end of the candle, so that there is a wick on either end. Then, after you set up your balanced seesaw and light each end, the candle should rock back and forth as long as there is wax left to burn.

• Long (10-inch) taper candle
  
• Kitchen knife (to be used only by an adult)
  
• Ruler
  
• 2 straight pins
  
• 2 identical drinking glasses
  
• 2 small saucers
  
• Matches
  
• Adult partner
  

1. Ask your adult partner cut about ½ to 1 inch off the bottom of the candle so that the wick is visible. It should stick out of the bottom just like it does the top.
   
2. Using the ruler, find the center of the candle and push one pin into each side of the candle at that point.
   
3. Carefully rest the pins on each glass so that the candle balances. It might take a few tries to get it just right. It should rock back and forth slowly.
   
4. Place one saucer under each end of the candle.
   
5. Light one end of the candle and let it burn until it starts to drip. When it does, light the other end and watch the candle begin to rock back and forth. You are truly “burning the candle at both ends.”
   

1. Why might it be important to light the ends of the candle one at a time instead of at the same time?
   

   

2. Imagine that you could place the candle high enough above the table that it would not touch the table if it tipped. How might the experiment change?
   

   

3. How might your results change if the candle were not uniform in shape, that is, thicker on one end, thinner on the other?
   

   

As you have probably noticed, some balls bounce better than others. For example, a football doesn't bounce all that high, but a golf ball will often bounce several times before coming to rest. These balls bounce the way they do because of what they are made of. But if you were to put some of the balls together, you would be amazed by the results.

Question: Which balls bounce best?

In this experiment, you will begin by dropping several balls of your choice, one at a time, from a predetermined height. You will measure their bounce height and record it in a data table. Then you will begin placing one ball on top of another and repeating the drops. This time, the heights to which the top ball bounces may surprise you. Your goal will be to determine which combination of balls produces the most impressive bounce of all.

When you drop a ball on the ground, some of its kinetic energy is transferred into the ground. The energy that remains is what makes the ball bounce back into the air. Some balls, such as golf balls and the super bouncy balls, retain most of the energy and bounce back to almost the same height from which they were dropped. However, other balls, such as bowling balls (which should never be dropped on the ground), lose almost all of their energy and if they do bounce back up, don't go very high in the air.

However, when you place one ball on top of another, some of the bottom ball's energy is transferred into the top ball after the bounce, which can make the top ball appear to fly into the air. The heavier the bottom ball is compared to the top ball, the greater the effect.

• Several round balls. Some possibilities are:— Basketball— Tennis ball— Rubber bouncy ball— Playground ball— Golf ball— Baseball
  
• Measuring tape
  
• Helper
  
• Open space for testing
  

1. Identify at least three balls you would like to use in the experiment.
   
2. Hold your arms straight out in front of you and have your helper measure their height above the ground. This will be the drop height for each of your trials.
   
3. With your helper ready to measure the bounce height, drop each ball by holding your arms directly in front of you and letting go of the ball.
   
4. Record the height to which each ball bounces.
   
5. Choose different pairings of balls to test. For example, you might select a tennis ball on top of a basketball.
   
6. Carefully hold the two balls at the same height as before with the one you chose to be on top sitting squarely on top of the bottom ball.
   
7. Drop the balls and have your helper measure the bounce height of the top ball. To double check, repeat this step until you feel confident in your measurement.
   
8. Repeat steps 5–7 as many times as you like. Be sure to try heavier balls on top of lighter balls as well.