Has anyone noticed that some things people believe actually don't make sense when you think about them? I'm talking about science, not superstition or myth. I think we should question our beliefs, just in case we miss any discoveries. Here are 2 examples:
In the experiment where you place a candle in a bowl of water and cover it with a glass, after a while the water rises and the candle goes out. People claim the water rises by 20% of the height of the glass, showing the oxygen is used up.
Some observant students noticed that when you use 2 candles, the water rises more! Does that mean 2 candles burn oxygen more completely? No, the reason the water rises is that the air, which used to be heated by the candle, cools after the candle goes out and contracts. This pulls the water up. 2 candles make the air hotter, which means it contracts more, pulling more water. The candle actually goes out before all the oxygen is used up.
To prove air has mass, 2 balloons are balanced on a scale. 1 balloon is popped. The other balloon sinks!
This experiment is totally flawed once you look at it. Obviously after popping and having rubber pieces flying everywhere, the other balloon will be heavier. An improvement is comparing an inflated balloon and an uninflated balloon. However, this still won't work because the experiment is immersed in air, so the buoyancy effect of air cancels the weight of air out. If you fill a balloon with water and have another empty balloon, and weigh both underwater, which will weigh more?