Editing Tyndall's Bar Breaker (section)

===Short Explanation===
Metals are very useful for a large number of reasons. They are strong, are good conductors, and have high melting points, which makes them ideal for building things. Although metals have a high melting point, they will still expand and contract in very small amounts as they heat up or cool down. The amount of force that two metals apply on each other can change due to how much they expand or contract, and it is the reason why the iron ingot broke.

As the iron bar was heated, it started to expand bit by bit, which is why we started tightening the nut for the bar. After heating it up until it was red hot, it had expanded so much that the nut could make a few full turns, meaning that the bar had expanded close to half an inch. After turning off the heat, the bar started contracting, and in doing so it started to pull harder on the iron ingot. Iron is a very strong metal, but it can be ''brittle'', meaning that it will break if hit with a high force instead of bending to absorb it. The iron ingot is absorbing more and more force as the bar continues to contract, until finally it cannot take anymore and breaks!