1. Warm-up Iron reacts with oxygen to form rust 1. Write the reaction with element symbols 2. Circle the reactants, box the products 3. If 20.1 g of iron have been used in the reaction and 23.8 g of rust are produced, how many grams of oxygen were used in the reaction? Show math and underline result!

2. Answer Fe + O → FeO 20.1 g Fe 3.7 g O 23.8 g FeO 23.1 – 20.1 = 3.0 g

4. Definition Chromatography is a physical method to separate homogeneous mixtures of substances by using a Solid phase: chromatography paper Liquid phase: water or solvents like alcohol, ether or acetone

5. Principle Substances in a mixture have different chemical properties and may vary in their solubility in the liquid phase adhesion to the solid phase therefore substances separate in form of different spots along the solid phase (paper) Identify substances by calculating Chromatography Reference Value = Rf

6. Rf values of separated bands solvent front A: 8 cm total 10 cm B: 4 cm start line

7. Chromatography Example

8. 1. measure the distance between start and solvent front 2. measure the distance between start and the center of each spot. 3. Calculate Rf = ____Height of spot (2) Height of solvent front (1)

9. Rf values Rf values are always numbers between 0-1! A high Rf value (0.9) means that the substance is close to the solvent front: very soluble A low Rf (0.1 or 0) means that the substance is not soluble

10. Rf values… Are independent of the length of the chromatography Rf values are relative: solvent front is further up…so are the spots Rf values are dependent on type of paper, type of solvent….

11. Journal # 2 Draw a chromatography strip where a mixture has separated into two spots, A, B, C with an A: Rf = 0.2 B: Rf = 0.8 C: Rf = 1.0 Label the chromatography and write a statement about the chemical characteristics of A, B and C.

12. Video Paper chromatography gas chromatography

13. Make a Venn Diagram to compare/contrast for chemical vs physical change