+ Divisions of Matter Pure Substances and Mixtures + Pure Substance Cannot be broken down and retain its properties. Has a fixed composition. Every sample of a pure substance has EXACTLY the same composition AND exactly the same characteristics - homogeneous Examples Salt NaCl Copper Water – H2O is always 11.2% Hydrogen and 88.8% Oxygen + Elements Simplest form of matter Made up of ONE type of ATOM All atoms in an element have same number of protons in nucleus. Atom- Smallest unit of an elements that KEEPS the IDENTITY of the element + PERIODIC TABLE Elements are represented by symbols NEED to know Symbols. (handout) 92 naturally occurring elements 93-112 Made only under lab conditions Information on periodic table Symbol Atomic # - which tells us the number of protons Atomic Mass – Average mass of the element (Number of neutrons plus protons) + + COMPOUNDS Made up of atoms from 2 or more different elements. Can be broken down into its elements BUT those elements have different properties than the compound. All samples of a compound have the same ratio of elements. Subscripts tell us the number of atoms or groups of atoms in a formula Coefficient (the number in front) refers to the entire unit. + Law of conservation of Energy The total amount of energy remains the same in a system. Energy can be absorbed or released in a system, it can change forms, but it is not destroyed or created. PAGE 11 IN YOUR BOOK + MIXTURES A mixture is a blend of two or more kinds of matter, each of which retains it’s own identity and properties. Web site to interact with KS3 Bitesize http://www.bbc.co.uk/schools/ks3bitesize/science + Mixtures http://www.bbc.co.uk/schools/ks3bitesize/science Homogeneous Uniform composition Same proportions of components throughout Also called solutions Examples Salt water Sugar water Stainless steel Heterogeneous NOT uniform throughout Heavier particles may concentrate at bottom of container 2 types/ colloids & suspensions Examples Granite Wood Blood Clay in water + Heterogeneous mixtures Suspensions Often large visible particles that tend to settle out Tend to block light Example: corn starch and water, clay and water Colloids Often suspended microscopic particles Exhibit Tyndale effect – which is when light is scattered by very small particles in its path , it makes a beam of light visible Example: gelatin milk, mayonnaise in water, + Tyndale effect: