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Introduction:
Before starting
this lab it is advisable to review the indicators of chemical change: change in temperature, precipitation, gas formation,
production of an electric current, change in chemical and physical properties, and color changes. It would be beneficial to
also review the splint tests for common gases.
This lab consists
of nine stations.
- Students ignite a piece of magnesium metal in a Bunsen burner.
- Students place a piece of platinum (or Ni-Cd) wire in a Bunsen burner.
- Students add calcium metal to water.
- Students add silver nitrate solution to sodium chloride solution.
- Students generate an electric current with copper and zinc strips in an acid solution.
- Students add silver nitrate solution to potassium chromate solution.
- Students add potassium permanganate to water.
- Students add vinegar to sodium bicarbonate powder and test for the gas produced.
- Students add ammonium chloride to water.
Estimated time to complete lab:
60-75
minutes. Students should be given at least 7-8 minutes per station to perform the lab, make their observations and decision,
and to clean up the station.
Equipment Required:
Station 1:
- 1 x 4cm piece of Mg for each group
- Bunsen burner
- Tongs
- Wire gauss
- Waste beaker
Station 2:
- Platinum (Ni-Cd) wire in holder or tongs
- Bunsen burner
- Steel wool
Station 3:
- Test tube in rack
- Water bottle with distilled (or de-ionized) water
- 1 freshly cut piece of Ca metal for each group
- Test tube clamp/tongs
- Waste beaker
- Test tube brush
Station 4:
- Dropper bottle of 0.1 mol/L sodium chloride
- Dropper bottle of 0.1 mol/L silver nitrate
- Test tube in rack
- Test tube brush
Station 5:
- 250 mL beaker
- Strip of copper
- Strip of zinc
- 2 wire leads with clips
- Galvanometer of voltmeter
Station 6:
- Dropper bottle of 0.1 mol/L potassium chromate
- Dropper bottle of 0.1 mol/L silver nitrate
- Test tube in rack
- Test tube brush
Station 7:
- Wash bottle with distilled (or de-ionized) water
- Small beaker with a tiny amount of potassium permanganate (only need 3-5 crystals for each group)
- Spatula
- Test tube in rack
- Test tube brush
Station 8:
- 250 mL beaker containing sodium bicarbonate
- Wash bottle containing vinegar (clearly marked)
- Scoopula
- Medium test tube in rack
- Wooden splints in 150 mL beaker
- Waste beaker for used splints
- Bunsen burner
- Test tube brush
Station 9:
- 250 mL beaker containing ammonium chloride
- Medium test tube in rack
- Scoopula
- Wash bottle with distilled (or de-ionized) water
- Test tube brush
- Rubber stopper to fit test tube
Safety Concerns:
- Wear safety glasses at ALL times during the lab.
- Station 1: Do not look directly at the metal when it ignites- use peripheral vision. Also, do not place
lab sheet or any other combustible near where the Mg will be held. In the unlikely event of a magnesium fire, DO NOT add water
to the fire – simple allow the Mg to burn out and then use a regular fire extinguisher if necessary.
- Station 3: Be sure to hold the test tube with a clamp/tongs as the reaction is extremely exothermic and
the calcium hydroxide produced can burn the skin. Do not allow the unreacted Ca to be placed down the sink, place it in a
waste beaker under reaction is complete, then dispose of it properly.
- Station 4 and 6: Silver nitrate, while not harmful, can stain the students’ hand after contact
(it is photo-sensitive).
- Station 5: Use Caution with the conc. Sulfuric acid (you may wish to use 3 or 6 mol/L acid instead- try
first)
- Station 7: Use caution with potassium permanganate – it is a strong oxidizer and can react with
skin quickly.
Clean Up Concerns: Do NOT allow the students to dispose of the calcium in station 3 down the drain. Other then that, have the students
use care and wipe down the lab bench with damp paper towel before leaving each station.
What Can Go Wrong:
- Students will try to “steal” any excess magnesium and calcium metal that is left out.
- Silver nitrate can cause a stain to appear on hands a couple of hours after the lab – this can
cause stress and phone calls at home if the students are not made aware of this potential occurrence.
- Potassium permanganate can stain and/or burn the skin with prolonged contact.
- Test tubes WILL get dropped during the cleaning process – have extras on hand.
- Have replacements available for all solutions and consumables as they will run out when it is most inconvenient
for you.
- Students will have trouble lighting the Bunsen burner if you do not review how to light it properly with
them.
Student Lab Sheet as a Word Document:
click here to download file
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