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Mixtures, Compounds, and Chemical Changes Slide 2 Compounds Compound: A pure substance consisting of two or more elements combined. Water - H 2 O (liquid) Salt - NaCl (solid) Methane - CH 4 (gas) Slide 3 Chemical Change A chemical reaction is required to separate a compound into separate parts. Chemical Reaction: Any change that involves the formation of a new substance. Formation of precipitate Change in color Formation of gas Temperature change Slide 4 Chemical Change A chemical change consists of two parts. Product: A substance formed by a chemical reaction. Reactants: The starting substances in a chemical reaction. 2 H 2 O 2 H 2 + O 2 Reactants Products Slide 5 Chemical Change Cake Recipe: Flour, Eggs, Sugar, Chocolate, etc. Beat together Bake Once baked, the ingredients are very difficult to separate! Slide 6 Chemical Change What chemical reactions occur in everyday life? Photosynthesis: 6 CO 2 + 6 H 2 O + light C 6 H 12 O 6 + 6 CO 2 Combustion: C 3 H 8 + 5 O 2 4 H 2 O + 3 CO 2 + energy Rust: 4 Fe + 3 O 2 + 6 H 2 O 4 Fe 2 O 3.nH 2 O Slide 7 Mixtures Mixture: Two or more elements that are mixed together but are not chemically combined. Mud - H 2 O + Dirt (Fe, K, Ca) Salt Water - NaCl + H 2 O Salad Slide 8 Mixtures Mixtures combine physically with no specific proportions. They just mix. Solids, liquids, and gasses can be combined to create mixtures. When creating a mixture, no new substances are formed. Each part of the mixture keeps its own properties. Slide 9 Mixtures Homogeneous Mixture: A mixture with the same uniform appearance and composition throughout. Homo prefix meaning same Heterogeneous Mixture: A mixture consisting of visibly different substances or composition. Hetero prefix meaning different Can you come up with some examples? Slide 10 Mixtures Simple mixtures can easily be separated by physical means. Simple Mixtures: Sand, Dust, Italian Dressing Mixtures can be separated in a variety of ways. Weight (centrifuge), Evaporation, Sifting, Magnetism.