Metals and Salts:  
There are several different classes if chemicals. In this section, we are going to talk about two of them; metals and salts. As you learn more chemistry, you will learn about other classes of chemicals.

Metals:
As we learned in the previous section, the elements to the left of the periodic table, with the exception of hydrogen are metals. Metals are usually, but not always hard. A piece of sodium can be cut with a knife! Some metals, such as sodium, are quite unstable, they will react with other chemicals easily and some metals such as gold are very stable and only combine with other chemicals very slowly. This is one reason why gold is so valued. Gold wedding bands stay as gold for a long time and only form chemical bonds with the oxygen in the air very slowly. Metals are usually shiny and can conduct heat and electricity well.

Have you ever put your hand on a piece of metal and observed that your hand became cold? This is because the metal is conducting the heat away from your hand, so your hand feels cold. Some metals are elements. Examples of such metals are gold, copper, iron and lead. Some metals are alloys, combinations of two or more metals – or sometimes a combination of a metal with a non-metal. The alloy steel is a combination of iron and carbon.

American coins are made of alloys. Dimes and quarters are made of three layers of metals. The inner layer is copper. The outer layers are an alloy of 75% copper, 25% nickel. These coins were originally made from silver, but silver became too expensive, so alloys were developed that had properties similar to silver, but were much less expensive. Alloys are used in many different ways – in aircraft, cars, bridges and buildings to name just a few.

Salts:
Salts are made when an element from the left hand side of the periodic table – a metal -chemically bonds with an element (or group of elements) from the right hand side of the table – a non-metal. There are many different kinds of salts. The substance in our kitchen that we call table salt is just one kind of salt and it is called sodium chloride. There are other salts often found in our houses – baking soda, and Epsom salts are just two examples.
Salts are solids at room temperature. Some are brightly colored and some are white. Some will mix with water (when something mixes with water, we say that it forms a solution in water or that it dissolves) and some do not. You know from your own experience that table salt dissolves in water. When salts dissolve in water, it is possible to pass an electric current through them. (This is why it is so important NOT to use electrical equipment in the bath. Though pure water cannot conduct an electric current, when we are in the bath, sweat from our body - mostly salt - dissolves in the bath water which can now pass a current, so you could be very seriously injured, if not killed). If you heat salts, to very high temperatures, they melt (turn to liquid) and when molten will conduct electricity.