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Matter

Matter. Objectives. State the important distinctions between compounds and mixtures. List seven ways to physically separate mixtures. Chemistry Question. Yesterday, we discussed the difference between mixtures and pure substances. What are the two kinds of pure substances?

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Matter

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  1. Matter

  2. Objectives • State the important distinctions between compounds and mixtures. • List seven ways to physically separate mixtures.

  3. Chemistry Question • Yesterday, we discussed the difference between mixtures and pure substances. • What are the two kinds of pure substances? • Today, we will discuss ways in which a chemist might separate a mixture in the laboratory.

  4. Compounds and Mixtures • Compounds are pure substances • Mixtures can never consist of only a single substance • Compounds can only be separated by chemical reactions. • Mixtures can be separated by physical changes

  5. Separation Techniques • Filtration • Separates liquid from a solid • The mixture is poured over a mesh-like filter paper and the liquid is allows to pass through, leaving behind the solid

  6. Separation Techniques • Density • Liquids of different densities will separate into layers. • The lowest density liquid will rest on top.

  7. Separation Techniques • Centrifuge • A centrifuge is a machine that separates solids from liquids by spinning very quickly. • This causes solids to fall to the bottom of the test tube, separating them from the liquids in the mixture.

  8. Separation Techniques • Decant • Separates solid from liquid by pouring the liquid off the top and leaving the solid behind • It can be difficult to ensure that all of the liquid is removed by this technique

  9. Separation Techniques • Magnetism • Can be used to remove magnetic solids from a mixture • This only works on elemental iron, not compounds containing iron

  10. Separation Techniques • Evaporation/Distillation • To separate a mixture of liquids, the liquid can be heated to force components, which have different boiling points, into the gas phase. The gas is then condensed back into liquid form and collected.  • Can be used to separate several different substances

  11. Separation Techniques • Chromatography • Techniques which use a stationary phase and a mobile phase to physically separate substances. • A solvent is a substance that dissolves the components of the mixture.

  12. Separation Techniques • A sample of the mixture is placed on the paper (stationary phase). The solvent will then dissolve the components of the mixture. • The components of the mixture will move with the solvent (mobile phase) up the paper. • Based on the properties of each component (e.g., polarity) the components will travel at different speeds with the solvent. • Many complex variations, but basic principles stay the same

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