The Pros And Cons Of Chemical Reactions

Chemists perform chemical reactions as a way to change one chemical, or substance, into another. Chemical reactions are constantly happening all around you, and inside of you.

As just one example, if you leave your bike out in the rain, you might have seen that the shiny metal turns reddish-brown. This happens because a chemical reaction has turned the metal into rust (specifically, the iron in the metal is reacting with the oxygen in the air or water). Sometimes, chemical reactions form more than one product, though, and chemists need a way to separate and remove the product they want from all of the other material. One way they do this is with a process called recrystallization. The scientist dissolves the mixture of products in hot water, and then lets the mixture cool. As the

mixture cools, one product slowly appears as crystals, which can then be removed from the rest of the liquid, which has the other product.

Why do you think the crystals appear when the solution is cooled? It has to do with the fact that every solid that can be dissolved in water has solubility, which is the largest quantity of the solid that can be dissolved in the water to make a clear solution. When the water starts getting cloudy and you can see solid particles floating around that means no more solid can dissolve into the water and the solution (water and solid mixture) is saturated. But, the solubility of most solids increases as the mixture is heated, so more of the solid can be dissolved in