1. Experiments with Iron and Sulfur
HW 1-2

2. Iron Filings and Sulfur
Initial observation of iron filings: dark gray particles; attracted to a magnet
Initial observations of sulfur: yellow solid powder; not attracted to magnet

3. Experiment #1: Stirring iron filings and sulfur together
dark – gray filings and yellow powder still present
Iron filings can be removed with a magnet
Does this picture represent an element, compound or a mixture? How do you know?

4. This is a picture of a mixture
Each element retains its own properties (color, appearance, magnetic properties)
Iron can be removed from mixture by physical means (attraction to magnet)

5. Experiment #2: Heat mixture of iron filings and sulfur in a flame
Link to video

6. Heating Fe + S: Final observations
Dark black solid (different than reactants);
Final product is not magnetic; iron cannot be separated with a magnet

7. Experiment #2: Compound
Lines of evidence:
Color and change in magnetic properties = chemical change
Iron + sulfur → iron sulfide
Element + Element → Compound
Fe S → FeS or
Link to animation Fe + S
Chemical Bond
Link to summary video

8. Filtration – technique for separating solids from liquids

9. An orange colored liquid is separated into a clear, colorless liquid and an orange solid. Was the orange liquid an element, compound or mixture? How do you know?
Mixture: Solid and liquid separated by a physical process - filtration

10. A clear, colorless liquid is heated on a hot plate
A clear, colorless liquid is heated on a hot plate. After 15 minutes, the liquid has evaporated and only a white solid remains. Was the original liquid before heating an element, compound or a mixture?
Mixture: Solid was separated from liquid by evaporation – physical process.

11. Electrolysis of Water
Initial Observations: clear, colorless water present in tube interconnected tubes.
Phenolphthalein indicator is colorless; Salt dissolved in water to improve conductivity; Electrodes inserted in water connected to power supply.

12. Final Observations video link
Better video link
When electric current passes through, bubbles are observed at each electrode. Water levels drop. Volume of trapped gas is twice as much on one side than the other. One side becomes magenta color.

13. Chemical or Physical Change? Lines of evidence?
Color change; colorless→ magenta
Bubbles formed; gas produced
Different volumes of gas suggests different gases
How could you experimentally determine identity of gases?

14. Gases are hydrogen and oxygen
2 H2O (l) → 2 H2(g) + O2(g)
Hydrogen volume is 2X oxygen volume (H2O)
Chemical test: Burning splint
Hydrogen + burning splint = POP
Oxygen + Smoldering splint = reignites
Video link H2 test
Video link O2 test

15. Homework 1-3, p. 68, #35, 36
35) Add hot water to sample or add water and heat; Benzoic acid will dissolve in water but not charcoal. Filter to remove charcoal, and then cool filtrate to crystallize benzoic acid or evaporate off water to recover benzoic acid.
36) Distillation – solution is heated to evaporate water; vapor is then cooled so that it condenses back to liquid state. After all of water is evaporated away, NaCl will remain behind. This process consists of physical changes.