Beginning of Essay
I went online and found out a lot of information about . If you cover the tin and allow the water and air to cool down, the air will cool and contract, lowering the pressure in the tin. If it lowers enough, the partial vacuum will collapse the walls of the can! ....

Middle of Essay
.... and form the gas (water vapor) that makes up the bubbles you see in the boiling process. The standard temperature at which this occurs is 100 C or 212 F. In the very early stages of heating, you may see some small bubbles even though the water is only warm. This is some air that is dissolved in the cold water and is being expelled by the heating. This is not boiling. As the water nears the boiling point, some areas of the container close to the heat source may be hot enough to cause some boiling in that area which produces some local bubbles. To be sure that all of the water is "at the boiling point," you should wait until there is a lar ....