2.1: C LASSIFYING M ATTER

W HAT IS A PURE SUBSTANCE ? Matter that always has exactly the same composition. Examples: Table Salt and Table Sugar

S UBSTANCES Have a fixed, uniform composition Every sample has the same properties Classify substances into two categories: 1. Elements 2. Compounds

E LEMENTS An element is a substance that cannot be broken down into simpler substances. Have a fixed composition because it contains only one type of atom. No two elements contain the same type of atom. Chemists use symbols of one or two letters to represent elements. The first letter is always capitalized. If there is a second letter, it is not capitalized. Examples: C, Al, Au, O, Ne, H, He

C OMPOUNDS Always contains two or more elements joined in a fixed proportion A compound is a substance that is made from two or more simpler substances and can be broken down into those simpler substances. Once elements combine in a compound, their properties change. Example: Water is composed of the elements hydrogen and oxygen. Oxygen and hydrogen are gases at room temperature, but water is a liquid.

M IXTURES Properties of a mixture can vary because the composition is not fixed. Individual substances of the mixture retain some of their individual properties. Example: Salsa, you mix ingredients together but you can still taste each individual ingredient Two types of mixtures: Heterogeneous Homogeneous Classified by how well the parts of the mixture are distributed throughout the mixture.

H ETEROGENEOUS M IXTURE The parts of the mixture are noticeably different from one another

H OMOGENEOUS M IXTURE Substances are so evenly distributed that it is difficult to distinguish one substance from another.

C LASSIFICATIONS OF M IXTURES Solution Suspension Colloid Classified based on the size of its largest particles The size of the particles in a mixture has an effect on the properties of the mixture.

S OLUTION When substances dissolve and form a homogeneous mixture, the mixture that forms is called a solution. Ex: Windshield wiper fluid 2 Parts: Solute and Solvent

S USPENSION A suspension is a heterogeneous mixture that separates into layers over time. Ex: Muddy water

C OLLOID A colloid contains some particles that are intermediate in size between the small particles in a solution and the larger particles in a suspension. Like solutions, colloids do not separate into layers. You cannot use a filter to separate the parts of a colloid. Ex: Milk

R EVIEW Classifying Matter Graphic Organizer