White powder mix-up at the factory

A mix-up at the white powder factory means that your learners will get to conduct fascinating experiments and discover which of four powders they’ve been delivered.

This session should take 70 minutes.

Equipment

Apparatus

• Eye protection.
• Test tubes (including pyrex ones)
• Ignition tubes
• Test tube racks and holders
• Beakers
• Glass droppers
• Glass stirring rods
• Spatulas
• Microscope & slides.
• Bunsen burners
• Tripods
• Gauzes
• Heatproof mats
• Clampstands
• Balances
• Powerpack/leads/bulb
• Electrolysis cell (as a distractor)
• Universal indicator & indicator scales
• Litmus
• Limewater

Chemicals

White powders (solids should be powdered so that they are roughly of equal particle size, students are told what the 4 powders are).

Choose 4 powders (approximately 10 g of each) from the list:

• Magnesium oxide
• Sodium chloride
• Zinc oxide
• Ammonium chloride
• Sugar
• Citric acid
• Calcium carbonate
• Wax
• Hydrochloric acid (1 mol dm^–3) – 50 cm³
• sodium hydroxide (1 mol dm^– 3) – 50 cm³ 

Health, safety and technical notes

• Read our standard health and safety guidance here.
• Eye protection should be worn – goggles (BS EN166 3 when handling the sodium hydroxide) rather than safety glasses.
• Zinc oxide, ZnO is very TOXIC to aquatic life, see CLEAPSS Hazcard HC108b.
• Ammonium chloride, NH4Cl (s) is harmful if swallowed and an eye irritant. When it sublimes, do not inhale the vapour. See CLEAPSS Hazcard HC008.
• Sodium hydroxide solution, 1 mol dm^–3 NaOH (aq), is CORROSIVE to skin and eyes. See CLEAPSS Hazcard HC091a.
• Hydrochloric acid, 1 mol dm^–3 HCl (aq), is of low hazard. See CLEAPSS Hazcard HC047a.
• Dispoal: Solutions produced from zinc oxide should be kept for disposal. (It may be easier to precipitate as the carbonate, filter and store the solid). 

Possible approaches

The experiment is designed to make students think about how chemicals differ – physically and chemically. Tell students at the start of a lesson that they will need to ask permission if an “unusual test” is required. Students are in competition with other companies for the business. “Companies” will be penalised for breaking health and safety laws, e.g. not wearing eye protection, untidy work. 

Notes

This resource is part of a collection of problem-solving activities, designed to engage learners in small group work. Find out how to use these resources.