Eleven-year-old Emily, who bought a copy of Abacus at the Royal Ontario Museum shop during March Break said, "I couldn't put the book down!" Emily sent us an experiment to try. We've added a second part, to make it even more interesting.
Heavy balloons
You'll need:
two balloons of the same size; an empty glass bottle (like a wine bottle); baking powder; a teaspoon; vinegar, a sheet of paper.
Blow up one of the balloons several times, letting out the air each time. This stretches the rubber, making it easier to inflate. Add three teaspoons of baking powder to this balloons--you'll spill some, so do this over a sheet of paper. If you fold the paper in half after the first spoonful, you can use it to funnel in the spilt powder. Shake the powder to the bottom of the balloon.
Carefully pour half a cup of vinegar into the bottle, wiping the top dry afterwards. Then, holding the balloon by its opening, slip this over the top of the bottle, taking care not to spill any of the powder inside. Make sure the balloon is securely attached to the top of the bottle. Then, by lifting up the bottom of the balloon, shake all the powder into the bottle. Once the balloon is blown up, pinch off the top so it doesn't go down, remove from the bottle and tie it off with a knot.
Blow up the second balloon so it's the same size as the first, tying it off as before. If it's the same colour as the first balloon, use a marker so you can tell them apart.
Hold a balloon in each hand (by the neck), and lift them up as high as you can. Let them go, seeing which one hits the ground first. You could repeat the experiment standing on a chair. Try several more times. Which one always wins the race?
Explanation
Baking powder (sodium bicarbonate) reacts with vinegar (a weak acid, called acetic acid). This produces a gas, called carbon dioxide, which blows up the balloon (together with a salt, called sodium acetate). Carbon dioxide is much denser than air, so the balloon filled with this gas is heavier than the other one and therefore sinks faster.
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