Educating Risa

 

I mentioned in yesterday’s post that Jim did a neat science experiment with the boys on Sunday night, building on an experiment I did with them last year. I loved the simplicity of this experiment, and that it uses items most folks have at home already. Here’s what you’ll need: a large (mixing) bowl, a candle (if you plan to blog about this later, go with a coloured rather than white candle!), a small dish, baking soda, vinegar, and matches or a lighter:

Place the candle and little dish in the large bowl, and add baking soda to the little dish:

Now ask your kids what will happen if you pour vinegar into the dish of baking soda. If they’ve done the acids and bases experiment before, they’ll know it “bubbles.” Jim asked the boys if they knew what kind of gas was released (that caused the bubbles) in that experiment. Daegan guessed carbon dioxide, which is correct. Now light the candle:

Ask “will anything happen to the candle when I add the vinegar to the baking soda? Do you have a hypothesis?” In our case, Daegan guessed that the candle would go out, because (a) candles need oxygen to burn and (b) carbon dioxide is heavier than air. So Jim rephrased that and said, “OK, so let’s test the hypothesis that CO2 is heavier than air. If it is, the candle should go out, right?”

Pour the vinegar:

And see what happens:

The first time we did this, we got bubbles, and the candle flame flickered, but there was not enough CO2 to put the candle out (it probably didn’t help that Daegan was jumping around excitedly, creating air currents and hence continually mixing oxygen from the air back into the bowl.) But since science must be repeatable, repeat the experiment (blow into the bowl first to ensure there is a fresh oxygen supply).

Pour more baking soda and vinegar:

The candle flame is still visible (again, do this with a coloured candle if you are going to post pics. We saw the flames fine with our eyes, but not on film afterwards. You can just make out the flame by the wick in this pic):

The candle went out (note the wisps of smoke):

Yes, indeed, carbon dioxide (CO2) is heavier than air.

Have fun repeating this experiment at your house; if you blog about it, send me a link!