Elements, Compounds, & Mixtures

How can matter be classified? Atoms are the smallest unit of an element that maintains the properties of that element. Three major classes of matter: Elements Compounds Mixtures Atoms are the basic building blocks for all three types of matter.

What are pure substances? A pure substance is a substance that has definite physical and chemical properties such as appearance, melting point, and reactivity. Made up of one type of particle. Pure substances cannot be formed or broken down by physical changes. Elements and compounds are pure substances

Elements Elements : pure substance that cannot be separated into simpler substance by physical or chemical means. Elements can be classified as metals, non-metals, and metalloids.

Compounds CO2 NaCl H2O Compounds : pure substance composed of two or more different elements joined by chemical bonds. Compounds can be classified as acidic, basic, or neutral by measuring a special value known as pH. Acids have a pH value below 7 Ex: Vinegar Bases have a pH value above 7 Ex: baking soda Neutral compounds have a pH value = to 7 Ex: pure water

How can compounds be classified? Litmus paper: is used to test whether a compound is an acid or a base. Blue litmus paper turns red in the presence of an acid. Red litmus paper turns blue in the presence of a base.

Mixtures Mixture: A combination of two or more substances that are combined physically but not chemically. Mixtures can be separated by physical means Ex: pizza (pick out pepperoni) Centrifuge : separate mixture by the densities of the components. Blood

How can mixtures be classified? Homogeneous mixture: mixture with a uniform composition. Water + salt, tea,etc… Heterogeneous mixture: mixture that does not have a uniform composition. Ex: salad, water and clay, pizza, etc..

Suspension, Colloids, and solutions A solution is a homogeneous mixture of one or more solutes dissolved in a solvent. Solute: substance that is dissolve. Solvent: the substance in which a solute dissolves Ex: tea Suspension: mixtures in which the particles of a material are spread throughout a liquid or gas but are not too large to stay mixed without being stirred or shaken. Ex: snow globe

Colloids Colloids: a type of mixture that falls somewhere between suspensions and solutions. As in suspension: particles are spread through a liquid or gas but particles do not settle out quickly. As in solution: they look homogeneous Ex: milk and gelatin