 Matter can be classified into different categories. First of all, what is matter? Matter is anything that has mass and occupies space. Now, the main two categories for matter are mixtures and pure substances. How do you know we know if something is a pure substance or a mixture? First of all, in a pure substance, you won't see any difference within the substance. Everything looks the same. However, don't be fooled, there are some mixtures that do the same thing. The homogeneous mixtures do look all the same everywhere. That's what the homo in homogeneous means, the same. How do we distinguish between a homogeneous mixture and a pure substance? A homogeneous mixture can be further separated by physical separation techniques, such as filtration or distillation. For example, if I have salt water, I could use distillation or evaporation to get rid of the water and separate the water into the salt. And then the water, if it's distilled, would be a pure substance. And the salt, if we have only salt left, would be a pure substance. The other type of mixture that is possible is heterogeneous mixture. If you see that one, you know immediately that it's a mixture, because you actually see the different substances that it's made of. For example, in bubble tea, you can see the liquid and you can see the little solid particles floating around. So then you know immediately this is a heterogeneous, heteromeaning not the same mixture. On the pure substances side, so pure substances are materials that you cannot separate anymore with physical separation methods. So you have either elements or you have compounds. An element is basically a material that's made out of one element, hydrogen, oxygen, and so on. If we could be going in and zooming in and look at the individual atoms or particles in there, they would be all made of the same type of atoms or elements. A compound, for example, water, if we could zoom in a lot, would contain more than one element. For example, water, each water molecule has two hydrogen molecules that are attached to one oxygen molecule. However, they are attached in a way that you cannot separate them with physical methods. You could use chemical methods, but not physical methods to separate them. So you can filter water as much as you want. You cannot get the oxygen or the hydrogen apart from each other. So that's the main overview. You have matter, either it's a pure substance or a mixture. You have the homogeneous mixtures. You have the heterogeneous mixture and you have the elements and the compounds, which are pure substances. The tricky one is to distinguish homogeneous mixtures from pure substances because you can't really know by looking at it. It will just look the same, all the same everywhere. The distinction between elements and compounds is also quite more difficult. You cannot notice by just looking at this. You will actually have to do some experiments to figure it out.