Matter is anything that weighs an amount and takes up space. There are three main types of matter including solid, liquid and gas. These types of matter have different properties that make them different from the other types of matter. Solid and liquids can be seen with the eye. Gases can’t be seen. Solids do not change their shape, but both liquids and gases do change shape. The molecules in these types of matter differ also. The molecules in solids stay put and don’t move whereas the molecules in liquids and gases do move around. Most people learn about matter and mass in science class.