63-64 More on Physical and Chemical Changes

Great demos for evidence of a change (color change, precipitate, formation of a gas, change in temperature)

1. Making a gold penny (color change)



plain penny, penny soaked in zinc and NaOH, brass penny

•  Put 20 mL of NaOH (Sodium Hydroxide) and a couple zinc pieces in a 250 mL beaker on a hotplate, simmer - don't boil
• Add pennies, heat until they turn a "silver color" *I start these in the morning and pull a couple out each period, I have left them in over night - no problem
• Take penny out and rinse with water
• Heat over a flame source (alcohol, Bunsen or butane lab burner) about 3 seconds each side until it turns "gold" *careful - pennies melt!

Students will think this is magic, explain it is a mixture of 2 metals (alloy) copper and zinc which makes brass

2. Burning Magnesium (light and heat produced)

Magnesium Ribbon

3. Flame test (color change)

Use a wood splint (popsicle stick) soaked in water to burn metallic compounds
Sodium chloride (NaCl) Calcium chloride (CaCl₂) Potassium chloride (KCl) Copper chloride (CuCl₂) Strontium chloride (SrCl₂)

4. Mixing Vinegar & Baking Soda (formation of a gas, change in temperature)

5. Mixing Epsom salt & Sodium carbonate Solutions video, procedure (precipitate)