Genie in a bottle – Harry Potter style potion for World Book Day

by Fellowship Agency March 7, 2019

Check out this Harry Potter Potions Class inspired #WhatsInMyTray activity by Senior Science Technician Paul Cook demonstrating the CLEAPSS method for the catalytic decomposition of hydrogen peroxide.
For more videos by Paul Cook, visit his channel:
Twitter: @t_saviour

You will need:

  • 2 x Shallow Gratnells (F1) trays
  • 0.5g – 0.6g Manganese (IV) Oxide (powdered)
  • 25ml 100vol (30%) Hydrogen peroxide
  • 15cm Cotton thread
  • 8cm x 8cm 1ply tissue
  • 250ml Conical flask (borosilicate) with bung to fit (the bung should have a central hole through it for ventilation and is advisable to prevent pressure building in the conical if the reaction starts too early)
  • Heatproof mat
  • Safety screen
  • Filter funnel
  • 25ml Measuring cylinder
  • Spatula
  • Weighing boat
  • Sealed glasses/goggles
  • Protective gloves and clothing
  • Video recording device


  • Place the heatproof mat in to one of the shallow Gratnells trays.
  • Set up the safety screen to fully protect students from the reaction. Students should be at least 5 meters away.
  • Put on safety glasses and gloves.
  • Make the pouch by weighing out 0.5g – 0.6g of Manganese (IV) Oxide and placing it into the centre of the measured tissue piece. Gather the four corners of the tissue up carefully, being sure not to lose the powdered chemical from the pouch.
  • Close the pouch by tying a knot with the cotton thread and leave at least 10cm of the thread to suspend the pouch into the flask.
  • Get your video recording device set up ready to record the demonstration. This should be a safe distance away or behind a safety screen.

What to do:

  • Place the conical flask into the shallow Gratnells tray on the heat proof mat.
  • Working in the second shallow tray, use the measuring cylinder to measure 25ml of 100vol hydrogen peroxide and pour into the conical flask making sure to use a funnel so no liquid touches the neck of the flask. Place the used equipment back into the second shallow Gratnells tray.
  • Carefully lower the pouch into the conical flask just past the neck and hold in place using the bung to trap the thread, suspending the pouch well above the liquid.
  • Start your video recording.
  • When you are ready, pull the bung out to release the pouch and take several steps back, watching the potion bubble and the vapour rise out of the flask and into the tray.
  • Once the conical flask has cooled, tidy up the equipment and dispose of the reagents following all appropriate health and safety guidelines.
  • Share your video on social media using #WhatsInMyTray.

What is happening:

Manganese (IV) Oxide is a catalyst. It this demonstration, Manganese (IV) Oxide speeds up the decomposition of hydrogen peroxide to form water and oxygen.

This is the chemical reaction: 2H2O2(aq) → 2H2O(l) + O2(g)

The oxygen produced causes the liquid in the flask to bubble. This is an exothermic (heat producing) reaction. As the flask heats up, the water produced condenses out as vapour (visible as steam). The oxygen gas generated during the reaction forces the steam out of the flask creating the cloud of water vapour you can see. As Manganese (IV) Oxide is a catalyst, it is not consumed in the reaction.

Other things to try:

  • Filter, dry and weigh the catalyst at the end of the demonstration to show its recoverability and prove that it is not consumed in the reaction. Be sure to include any particles of Manganese (IV) Oxide that have escaped the flask, these will have been contained within the shallow tray.
  • Model this chemical reaction using molymod®.
  • If you like this demonstration, check out our Funky Foam activity, which uses yeast as an alternative catalyst.
  • Answer the following questions:
    • How can you prove that the gas produced in this reaction in oxygen?
    • What happens if you use a larger amount of catalyst? How would you measure this?
    • Why does the reaction stop?

Health & Safety

As with all Gratnells Learning Rooms What’s In My Tray Activities, you should carry out your own risk assessment prior to undertaking any of the activities or demonstrations. Ensure that protective eyewear, clothing and gloves are worn when preparing and performing this demonstration. When presenting, ensure students are at least 5 metres from presentation area and are all wearing protective eyewear. This is a very exothermic reaction so care should be taken. Leave equipment to cool before handling. Hydrogen peroxide solution is corrosive and manganese (IV) oxide is harmful if swallowed or inhaled. This demonstration should only be carried out by an appropriately qualified individual. Follow all relevant CLEAPSS guidelines.