Science 7–10 · Years 9–10

Getting a metal from its oxide: heating copper(II) oxide with charcoal

Reactions

PracticalMedium risk

School laboratory, not for home

In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

The idea

Carbon is more reactive than copper, so heating copper(II) oxide with charcoal removes the oxygen and copper metal remains, the reaction behind extracting metals from their ores.

Safety card

Medium riskA teacher supervises

Setting: In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

Hazards

copper(II) oxide is harmful if swallowed and toxic to aquatic life
hot glass and powder; the mixture can spit
carbon monoxide can form when carbon is in excess
charcoal can smoulder long after heating

Controls

eye protection; tube mouth pointed away from people
well-ventilated laboratory
all charcoal residue soaked in water before it goes to the bin
copper residues to labelled waste

Note

NSW Department of Education, Chemical Safety in Schools (CSIS) 2021 Technical Update: Section 1.7 (risk assessment before use) and Volume 2 Appendix D (generic assessment advice, user codes and DoE categories). Complete a RiskAssess or CSIS site-specific risk assessment before the lesson. CSIS Appendix F (charcoal) warns that charcoal smoulders long after heating and has caused fires in schools, and describes this mixed-powder method in a test tube held horizontally.

What you need

copper(II) oxide 2.00 g and charcoal powder about 0.3 g (an excess), weighed to 0.01 g
borosilicate test tube, clamp stand or test-tube holder, Bunsen burner, heat-resistant mat
balance reading to 0.01 g, 250 mL beaker of water, spatula, hand lens

How to do it

Weigh the empty test tube, add the copper(II) oxide and the charcoal, mix them, and weigh again.
Hold the tube horizontal (the method CSIS Appendix F describes) and heat the mixture strongly for 5 minutes; watch for a glow spreading through the powder.
Let the tube cool completely on the mat, then weigh it again and calculate the mass lost.
Tip the cooled solid into the beaker of water and stir: charcoal floats and dense grains sink. Examine the grains with the hand lens.
Write the word equation and the balanced equation 2CuO + C gives 2Cu + CO2, and explain why carbon can take the oxygen from copper but not from magnesium.

What you should see

Pink-brown grains of copper appear where the black powders met and sink in the water while the excess charcoal floats. 2.00 g of copper(II) oxide can give at most 1.60 g of copper and needs only 0.15 g of carbon. If all the oxygen leaves as carbon dioxide the tube loses 0.55 g; a smaller loss shows the reduction was incomplete, and a larger one means some of the excess charcoal burnt in air or some oxygen left as carbon monoxide (0.70 g if all of it did). The learner knows it worked when copper-coloured grains that sink in water are found and the tube has lost mass.

What changes

This activity lists no variables to change, measure and keep the same.

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

The copper was already in the tube as copper and the heat just cleaned it.
Charcoal only burns; it cannot take part in a reaction with another substance.
Any metal can be extracted by heating with carbon.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Science 7–10 Syllabus (2023)SC5-RXN-01 SC5-WS-04
Australian Curriculum v9AC9S9U07AC9S10U07

Sources

The pages the author read to write this activity.

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