Classifying Matter Pure substance – every sample of a given substance has the same properties because a substance has a fixed, uniform composition. Element – An element has a fixed composition because it contains only one type of atom.  Examples: Gold, Aluminum, Carbon, Chlorine Atom – smallest particle of an element Compounds – always contains two or more elements joined in a fixed proportion

Hydrogen/Oxygen/Water Would you put oxygen or hydrogen on a fire to put it out? Can you breathe in water?

Hydrogen/Oxygen/Water At room temperature, hydrogen and oxygen are a gas. At room temperature, water is a liquid. Four states of matter: Solid, Liquid, Gas, Plasma. Each element and compound has a different temperature that causes them to change phase.

Boiling/Freezing Points Each element and compound has a different boiling and freezing point Freezing point for water? Boiling point for water? Liquid to solid? Liquid to gas? Solid to liquid? Gas to liquid? Solid to gas? Gas to solid?

Phase Change Diagram

Classifying Matter Mixtures – properties of mixtures can vary because compositions are not fixed.  Heterogeneous mixture. You can see individual portions of said mixture. An example is sand.  Homogeneous mixture. You cannot see individual portions of said mixture. Solutions. Sugar in water. Suspensions. Italian salad dressing. Colloids. Fog, milk.

Physical Properties Viscosity – resistance to flowing (e.g. honey has high viscosity) Conductivity – ability to allow heat to flow Malleability – ability of solid to be hammered without shattering Hardness – ability to scratch another substance Melting/Boiling Points Density – ratio of mass of a substance to its volume

Chemical Properties Flammability – ability to burn in presence of oxygen Reactivity – how readily a substance combines with other substances

Is a Change Chemical or Physical? When matter undergoes a chemical change, the composition of the matter changes. When matter undergoes a physical change, the composition of the matter remains the same.