Experiments with Iron and Sulfur HW 1-2

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

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?

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)

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

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

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

Filtration – technique for separating solids from liquids

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

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.

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.

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.

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?

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

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.