did you know that Ancient metalworkers in East Africa knew the secrets of strengthening their iron. They knew that if they melted their iron in a furnace fired with coal, then when it cooled and solidified it would be harder than the original iron. What really happened inside the hot furnace? Coal is a form of carbon, so when its heat melted the iron, tiny particles of carbon dissolved into the liquid iron. This formed a solution. When the mixture of carbon and iron cooled and solidified, it was much harder than the original iron. Since it was harder, it was much more useful for building things like tools and weapons. This solution of carbon dissolved in iron is called steel. Every time you use a tool made out of steel, you are benefiting from the discoveries of those ancient metalworkers from long ago.