See oxygen being released
Compare oxygen bubbles in a dilute peroxide solution with and without a small, pre-tuned catalase dose. A quick demonstration can lead into measuring a rate with appropriate apparatus.
Use these original S&T teaching drafts after a teacher or technician has piloted the exact product, substrate and assay. Recipes and timing targets are proposed starting conditions, not validated performance claims. Review current SDS and institutional guidance; wear eye protection, avoid enzyme aerosols and splashes, and keep powders under technician control. No tasting. Keep controls at the same final volume, pH, temperature and stirring conditions. Plan reagent-specific waste disposal.
Catalase in nature
Cells form hydrogen peroxide during normal metabolism. Catalase helps prevent peroxide accumulation by converting it to water and oxygen. It is found in many organisms, including plants, animals and microorganisms: it is one part of the cell’s protection against oxidative damage.
What chemical reaction does it catalyse?
Enzymes speed up a reaction without being consumed in the overall process. The preparation, accessible substrate and reaction conditions determine what you can measure.
Industrial applications
Catalase removes residual hydrogen peroxide in food processing, textiles and other processes that use peroxide as an oxidising agent.
Experiment overview
Compare oxygen bubbles in a dilute peroxide solution with and without a small, pre-tuned catalase dose. A quick demonstration can lead into measuring a rate with appropriate apparatus.
Equipment and materials per working group
- Two open test tubes in a rack and two pipettes
- Technician-prepared 0.3% w/v hydrogen peroxide
- Catalase working dilution, timer and tray
- Eye protection; optional suitable gas-collection apparatus for a later rate study
Plan a class of 30
Use 10 working groups of three. Multiply the per-group quantities in this guide by 10, then allow an appropriate preparation reserve. Keep concentrations unchanged when scaling. Assign a timer, a practical operator and a recorder, then rotate roles. Set up teacher-prepared comparison samples in advance where a reaction takes longer than the lesson.
Teacher and technician preparation
- Prepare 0.3% hydrogen peroxide from a suitable school reagent under technician control.
- Pilot a 1:10,000 catalase dilution first: this S&T stock is very active. Adjust dilution to give steady, manageable bubbling rather than frothing or splashing. Do not use undiluted concentrate for this demonstration.
- A higher dose is not automatically better. Keep vessels open, use small volumes and avoid foam-enhancing additives.
Use enough working enzyme to make a clear comparison in the intended time window. Do not automatically add more concentrate: reactions can finish before measurement, stocks can alter pH or background colour, and some substrates remain slow even at a high dose. Pilot the proposed recipe, then record the final preparation and dilution on the results sheet.
Step-by-step class method
- Label tubes ENZYME and CONTROL and place them in a tray.
- Add 5 mL of 0.3% peroxide to each at room temperature.
- Record the appearance before adding enzyme.
- Add 0.1 mL of the pilot-selected working enzyme to ENZYME and 0.1 mL matching diluent to CONTROL.
- Start the timer and observe without putting your face over the tubes.
- Record bubbling at 15 seconds, 30 seconds, 1 minute and 5 minutes. Do not stopper the tubes.
- Discuss which tube generates gas more quickly; bubbling scores are qualitative, not a calibrated oxygen volume.
- For a later investigation, use an approved gas-collection method and compare a series of working dilutions.
What should students look for?
Rapid oxygen formation in the enzyme tube should contrast with little change in the control. Peroxide can also decompose without enzyme, especially if contaminated.
Interpretation and troubleshooting
Do not use concentrated peroxide, sealed vessels or flame tests. Enzyme addition must not cause splashing; dilute further before pupils begin if it does.
Questions for the class
- What changed in the enzyme-treated sample compared with the control?
- What bond or substrate does this enzyme act on?
- Which conditions did we keep the same, and why?
- Could colour, pH, warming, stirring or background sugars explain part of the result?
- What would you measure or change in a follow-up investigation?
Your investigation sheet
Name: ____________________ Group: ______ Date: __________
Prediction: _______________________________________________________
Enzyme preparation / batch: ________________________________________
Final working dilution and dose: ____________________________________
Substrate: _______________ pH: ______ Temperature: ______ °C
| Time / min | Enzyme + substrate | No-enzyme control | Enzyme-only blank / notes |
|---|---|---|---|
| 0 | ________________ | ________________ | ________________ |
| 2 | ________________ | ________________ | ________________ |
| 5 | ________________ | ________________ | ________________ |
| 10 | ________________ | ________________ | ________________ |
| Later: ___ | ________________ | ________________ | ________________ |
Conclusion supported by our control: _________________________________
One limitation and one improvement: __________________________________
Background sources and product details
This is an original teaching adaptation. External methods establish useful principles and assay formats; they do not validate the suggested doses for S&T preparations.