Siyapath
Sign up

Lesson: Chapter 3 — The Structure of Matter

Introduction 2 of 4

Sorting matter into kinds

Matter is sorted in two quite different ways: by how it behaves physically, and by what it is chemically made of.

By physical nature

The familiar three: solid, liquid and gas.

By chemical composition

This is the division that matters for the rest of the chapter. Matter is either a pure substance or a mixture, and each splits again.

  • Pure substances
    • Elements — one kind of atom only: iron (Fe), oxygen (O2), copper (Cu), nitrogen (N2)
    • Compounds — different elements chemically joined: water (H2O), carbon dioxide (CO2)
  • Mixtures
    • Homogeneous — the same throughout: a salt solution, a sugar solution
    • Heterogeneous — not the same throughout: sand and water, sand and salt

Figure to be added

The classification tree for matter: matter branching by physical nature into solid, liquid and gas; and by chemical composition into pure substances (elements, compounds) and mixtures (homogeneous, heterogeneous), with the examples above under each branch.

What this shows

Notice where the boundary falls. A compound is a pure substance even though it holds more than one element, because those elements are chemically joined in a fixed way. A mixture is not: the things in it are merely mingled, and each keeps its own properties.