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Understanding Mixtures: Heterogeneous vs. Homogeneous and Chemical Changes

This article explores the concepts of mixtures, focusing on the differences between heterogeneous and homogeneous mixtures. Heterogeneous mixtures, like chicken noodle soup, display uneven composition, while homogeneous mixtures, termed solutions, have uniform composition throughout, such as vinegar and olive oil. The piece also explains methods for separating mixtures based on physical properties and emphasizes the significance of physical versus chemical changes, including indicators of chemical reactions and the Law of Conservation of Mass.

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Understanding Mixtures: Heterogeneous vs. Homogeneous and Chemical Changes

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  1. Matter and Change

  2. Mixtures • Mixture: A physical blend of two or more components. • Salad • Chicken noodle soup

  3. Heterogeneous vs. Homogeneous • Heterogeneous Mixtures • A mixture in which the composition is not uniform throughout. • Chicken soup ingredients are not evenly distributed. • Homogeneous Mixtures • A mixture in which the composition is uniform throughout.

  4. Homogeneous Mixtures • Solution: Another name for a homogeneous mix. • Many are liquids • Can be gas (air) • Can be a solid (stainless steel = iron + chromium = nickel) • Phase: Term used to describe any part of a sample with uniform composition and properties. • Homogeneous mix. contains one single phase.

  5. Homogeneous Mixtures = Olive oil (Olive’s oil and different waxes) Vinegar (water and acidic acid)

  6. Homogeneous Mixtures Both are mixtures • Olive oil • Vinegar (water and acidic acid) • When mixed together they form layers. • Both layers are phases. • The oil phase floats on the water phase.

  7. Separating Mixtures • Differences in Physical properties can be used to separate mixtures. • Separating Olive oil and Vinegar • Method one: pour off the oil. (oil floats on water) • Method two: freeze. Oil freezes before vinegar.

  8. Separating Mixtures Filtration: separating a solid from a liquid. Distillation: boiling a liquid to produce a vapor then condensed into a liquid.

  9. Section 2.4 Chemical Rxn. • Physical Change: some properties of a material changes but the composition does not. • Chemical Change: composition of matter always changes. • Chemical property: The ability of a substance to undergo a specific chemical change. • Ex. The ability to rust.

  10. Chemical Properties. Are important because they can be used to identify a substance. Can be observed only when a substance undergoes a chemical change.

  11. Physical Δ vs. Chemical Δ Physical Change: Iron and sulfide get separated with the use of a magnet. Chemical Change: Iron and oxygen form rust.

  12. Chemical Reactions Substance present at the beginning Substance produced When one or more substances change into one or more new substances. A chemical change is also called a chemical Rxn. Reactant Product

  13. Chemical Reactions Substance present at the beginning Substance produced Reactant Product

  14. 4 Clues to Chemical Changes • Transfer of Energy • Every chem. Rxn involves energy. • A change in color. • Cooked food browns illustrating a chem. Change. • The production of a gas. • The bubbles from soap scum and cleaner. • Formation of a precipitate. • Our demo on Tuesday.

  15. Law of Conservation of Mass In any physical change of chemical reaction mass is neither created or destroyed. During a chemical reaction the mass of the products is always equal to the mass of the reactants.

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