We have already learned that all of the stuff that makes of the Universe can be grouped into one of two entities. The stuff is either matter or it is energy. Albert Einstein proposed that matter and energy are related to each other with his concept called the mass-energy equivalence, E = mc2. His theory states that matter can be converted in the energy and energy can be converted into matter.
We will explore energy in later lessons. First, we must understand matter. We know that matter is anything that has mass and takes up space. This is an extremely broad definition that includes everything that we can see around us. Let me introduce some more specific classifications of matter so we can better understand differences among types of matter.
Matter can be separated into two main groups: mixtures and pure substances.
Mixtures are a physical combination of two or more substances. Sometimes you can see the different parts of a mixture like in salad or a pizza. Sometimes you cannot see the different parts of a mixture like a teaspoon of sugar mixed into some hot tea or tap water.
A heterogeneous mixture is one which you can see the different parts of the mixture. We would say that the components of this type mixture are not uniform throughout, like pizza.
A homogeneous mixture is one which you cannot see the different parts of the mixture. We would say that the components of this type of mixture are uniform throughout, like tap water.