1. Close your books and take out a piece of paper. Give an example of each of the following. 1)Element that exist as a solid at room temperature (298.15K) 2)Element that exists as a liquid at RT 3)Element that exists as a gas at RT 4)Compound that exist as a solid at RT 5)Compound that exist as a liquid at RT 6)Compound that exist as a gas at RT

2. Close your books and take out a piece of paper. Give an example of each of the following. 7) Solid-solid solution 8) Solid-liquid mechanical mixture 9) Liquid-liquid homogeneous mixture 10) Liquid-gas heterogeneous mixture 11) Gas-gas homogeneous mixture

3. Phase Changes

4. Phase Changes (Changes in State) Chemical or physical? – Physical Which ones do we have? – 6 main ones: s ↔ l, s ↔ g, l ↔ g Which points separate the phases? – Melting or freezing point and boiling point

5. Phase Changes

6. Changes of State in Water Boiling point of water = 373.15K Melting point of water = 273.15K Freezing point of water = 273.15K Notice that these are the same? They are interchangeable

7. What Happens During Phase Changes? In other words “what happens at the melting & boiling points” At melting & boiling points, the temperature doesn’t change until all of the substance has changed phase regardless of how much heat you add or remove

8. What Happens During Phase Changes? Particles can’t absorb any more heat so the extra heat is used to change phase, which is why there is no temperature change during phase changes E.g. when an ice cube melts, it will stay at 273.15K until all the solid becomes liquid even if it’s 373.15K outside

9. Heating “Curve” of H 2 O

10. Separation Techniques

11. Hand separation Filtration Extraction Fractional distillation Chromatography Centrifugation Evaporation Distillation Solvent extraction Recrystallization Gravity separation

12. Separation Techniques Which types of matter can we separate? Why?

13. Filtration Separates liquid-solid mixtures Filter paper: lets liquid through, keeps solids out Vacuum filtration: water flow creates vacuum in filter flask and sucks air through the filter paper

14. Filter Paper

15. Vacuum Filtration

16. Chromatography Separates liquid-liquid mixtures A mixture carried by a solvent through a stationary medium (solid column, filter paper) Separation occurs when components of the mixture move through the medium at different speeds

17. Paper & Thin Layer Chromatography Solvent can be a number of things (H 2 O, ether, ethyl acetate) Stationary medium: chromatography paper

18. Paper & Thin Layer Chromatography “Spot” your chromatography paper with your mixture near the bottom Put your paper in the container with solvent Solvent will go up the paper and carry the mixture up with it Components will separate if they travel at different speeds

19. Paper & Thin Layer Chromatography

20. To identify the components of a mixture, use Rf values Rf = distance traveled by component distance traveled by the solvent Compare experimental Rf values with reference Rf values to identify your components

21. Evaporation Separates solid-liquid mixtures Boil away liquid to leave the solid E.g. salt production: evaporate water from seawater to get salt Can this method be used for liquid-liquid mixtures?

22. Evaporation of Sea Water

24. Distillation Separates liquid-liquid mixtures Uses different boiling points of liquids When would this method not be useful?

25. Distillation Liquid with the lowest boiling point evaporates 1 st Gas is cooled and collected elsewhere Once all of the 1 st liquid is collected, repeat for the liquid with the next lowest boiling point

26. Distillation