Catalysts: manganese dioxide and liver speed up the breakdown of hydrogen peroxide

The idea

A catalyst increases the rate of a reaction without being used up, so the same amount of product forms sooner and the catalyst can be recovered.

Safety card

What you need

• hydrogen peroxide 3 percent w/v (10 volume), 20 mL per run
• manganese(IV) oxide 0.10 g, weighed; 1 cm cube of raw potato; 1 cm cube of liver; the same cubes boiled for 5 minutes as controls
• 100 mL measuring cylinders (one per catalyst and one with none), a squirt of washing-up liquid, stop clock; for the quantitative run a 250 mL conical flask with bung and delivery tube to a 250 mL measuring cylinder inverted over water (the run gives about 223 mL over water, more than a 100 mL gas syringe holds); filter funnel, filter paper and a balance reading to 0.01 g for recovering and reweighing the catalyst

How to do it

1. Foam race: put a squirt of detergent and 20 mL of peroxide in each cylinder, add one catalyst to each and time how long the foam takes to reach the 100 mL mark; leave one cylinder with no catalyst.
2. Quantitative run: put 20 mL of peroxide in the flask, add 0.10 g of manganese(IV) oxide, bung at once and record the gas volume every 15 seconds until it stops changing.
3. Filter the black solid from the quantitative run, dry and weigh it; compare with 0.10 g.
4. Repeat the foam race with the boiled potato and liver and compare.

What you should see

No foam forms without a catalyst in the time of the lesson. Manganese(IV) oxide and liver foam within seconds; raw potato is slower; boiled potato and liver give almost nothing because the enzyme catalase has been destroyed. 20 mL of 3 percent hydrogen peroxide can give up to 216 mL of dry oxygen at 25 °C, about 223 mL once collected over water and saturated with water vapour (3.17 kPa at 25 °C); the collected volume levels off near 223 mL. The black solid is recovered still black and still in the same form, which is the evidence that it was not used up; its mass is not expected to match the 0.10 g weighed out, because some of it stays on the flask wall and in the filter paper and a balance reading to 0.01 g can place 0.10 g no closer than about 10 percent either way. The learner knows it worked when the collected volume levels off near the calculated 223 mL and the catalyst is filtered off unchanged, with a recovered mass between about 0.08 g and 0.10 g.

What changes

What you change

catalyst (none, manganese(IV) oxide, raw potato, raw liver, boiled potato, boiled liver)

What you measure

time for the foam to reach 100 mL, or gas volume against time

What you keep the same

• volume and concentration of peroxide
• temperature
• amount of detergent
• cube size

Common misconceptions

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

• The catalyst is a reactant that gets used up.
• A catalyst makes more product.
• Enzymes are not catalysts because they come from living things.

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-02SC5-WS-06
• Australian Curriculum v9AC9S10U07AC9S10I06

Sources

The pages the author read to write this activity.

1. curriculum.nsw.edu.au/learning-areas/science/science-7-10-2023/outcomes
2. edu.rsc.org/experiments/hydrogen-peroxide-decomposition-using-different-catalysts/831.article
3. edu.rsc.org/experiments/testing-for-catalase-enzymes/425.article
4. education.nsw.gov.au/content/dam/main-education/asset-management/chemical-safety/5._Volume_2_Appendices.pdf