Warmup – States of Matter

1. Warmup – States of Matter List one property that solids and gases share. List three properties they do not share. Describe the movement of particles in a liquid.

2. Mixtures vs Pure Substances Compounds vs Elements

3. A sample of matter Can it be separated by physical means? YES NO MIXTURE PURE SUBSTANCE (> 1 kind of atom and/or compound)(only 1 kind of atom OR compound)

4. Mixtures vs Pure Substances Compounds vs Elements

5. Let’s focus on mixtures first Is the composition uniform? YES NO HOMOGENEOUS HETEROGENEOUS e.g. lemonade, steel e.g. blood, dirt, milk

6. Mixtures vs Pure Substances Compounds vs Elements

7. Now let’s look at pure substances Can it be decomposed by ordinary, chemical means? YES NO COMPOUNDELEMENT (> 1 kind of atom)(only 1 kind of atom) e.g. water, salt e.g. gold, iron

8. Let’s turn to elements (only 1 kind of atom) One atom? Monatomic Two atoms? Diatomic Three atoms? Triatomic More than one form? Allotropic Oxygen: O2, O3 Carbon: graphite, diamond

9. Mixtures vs Pure Substances Compounds vs Elements

10. Elements and Compounds • Compound: • made up of 2 or more elements • can be broken down chemically • e.g. H2O, NH3, CO2 Element: • simplest form of matter – contain only 1 kind of atom • cannot be broken down further by chemical means • e.g. C, N2, O2, H2

11. Elements and Compounds Example of the breakdown of a compound  its elements cane sugar C12H22O11 chemical change C + H2O (element)(compound) chemical change H2 + O2 (element)(element)

12. Elements and Compounds • In general, chemical and physical properties of elements DIFFER from those of the compounds they make. • e.g. H2(gas)and O2(gas) vs. H2O(liquid)

13. Physical Separation of Mixtures ProcessProperty exploited Filtration solubility Crystallization solubility Evaporation boiling point Distillation boiling point Centrifuge density Decant density Magnetism magnetism Sifting size or shape Chromatography size/polarity/charge

14. Filtration vs Decanting Decant Denser substance drops to bottom of beaker, less dense portion can then be poured off the top Filter Substance must be dissolved or suspended in water

15. Fractional Crystallizatione.g. separation of radium chloride from barium chloride by Marie and Pierre Curie

16. Distillation

17. Chromatography The separation of chemical substances by differential movement through a two-phase system Applications in chemistry: Analytical chemistry – separating out components of a mixture before identifying each component Synthetic chemistry – purifying compounds History Earliest chromatography – Mikhail Tswett – 1906 – separated plant pigments (colored, hence “chroma”) by paper chromatography.

18. Some Chromatography Terms Mobile phase = the phase which moves across the stationary phase, into which the sample is often placed (= liquid solvent in liquid chromatography) Stationary phase = the phase which remains in the same place, over which the mobile phase moves, may be attached to or contained within a support (= paper in paper chromatography) Mixture is dissolved in the mobile phase, moves up the paper (stationary phase) by capillary action.

19. Paper Chromatography The paper and the solvent “compete” for the substances in the mixture. Substance more attracted to the solvent? Moves a long way up the paper Substance more attracted to the paper? Does not move very far – adsorbs to the surface of the paper

21. Paper Chromatography Compare components of a mixture: Rf = how far the substance moves up the paper how far the solvent moves up the paper