Burning in pure oxygen

Pure oxygen inflames a smoldering splint!

Difficulty:
Danger:
Duration:
10 minutes
Experiment's video preview

Reagents

Safety

  • Put on protective gloves and eyewear.
  • Conduct the experiment on the plastic tray.
  • Keep a bowl of water nearby during the experiment.
  • Remove protective gloves before lighting the splint.
General safety rules
  • Do not allow chemicals to come into contact with the eyes or mouth.
  • Keep young children, animals and those not wearing eye protection away from the experimental area.
  • Store this experimental set out of reach of children under 12 years of age.
  • Clean all equipment after use.
  • Make sure that all containers are fully closed and properly stored after use.
  • Ensure that all empty containers are disposed of properly.
  • Do not use any equipment which has not been supplied with the set or recommended in the instructions for use.
  • Do not replace foodstuffs in original container. Dispose of immediately.
General first aid information
  • In case of eye contact: Wash out eye with plenty of water, holding eye open if necessary. Seek immediate medical advice.
  • If swallowed: Wash out mouth with water, drink some fresh water. Do not induce vomiting. Seek immediate medical advice.
  • In case of inhalation: Remove person to fresh air.
  • In case of skin contact and burns: Wash affected area with plenty of water for at least 10 minutes.
  • In case of doubt, seek medical advice without delay. Take the chemical and its container with you.
  • In case of injury always seek medical advice.
Advice for supervising adults
  • The incorrect use of chemicals can cause injury and damage to health. Only carry out those experiments which are listed in the instructions.
  • This experimental set is for use only by children over 12 years.
  • Because children’s abilities vary so much, even within age groups, supervising adults should exercise discretion as to which experiments are suitable and safe for them. The instructions should enable supervisors to assess any experiment to establish its suitability for a particular child.
  • The supervising adult should discuss the warnings and safety information with the child or children before commencing the experiments. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
  • The area surrounding the experiment should be kept clear of any obstructions and away from the storage of food. It should be well lit and ventilated and close to a water supply. A solid table with a heat resistant top should be provided
  • Substances in non-reclosable packaging should be used up (completely) during the course of one experiment, i.e. after opening the package.

FAQ and troubleshooting

Where do I take hydrogen peroxide H2O2?

You may purchase hydrogen peroxide at any local pharmacy. Generally, they sell 3% solution, but 10% solution would work as well.

My experiment failed. What to do?

Make sure that at the moment you lower the splint into the flask, it is still smoldering, and you do not touch the solution.

Besides, hydrogen peroxide you are using might have decayed, so it doesn’t produce enough oxygen to ignite the splint. Buy fresh hydrogen peroxide and repeat the experiment.

Step-by-step instructions

Take the hydrogen peroxide solution.

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Some compounds, for example, manganese oxide catalyze hydrogen peroxide decomposition.

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Prepare a smoldering splint.

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Hydrogen peroxide decomposes into oxygen and water. Oxygen fills the flask and reacts intensively with the smoldering splint. It lights up again!

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Disposal

Dispose of solid waste together with household garbage. Pour solutions down the sink. Wash with an excess of water.

Scientific description

Why does a smoldering splint ignite?

Smoldering is a flameless and slow form of combustion. The organic substances on the surface of the splint react with the oxygen in the air. A splint smolders relatively slowly and over time may die away.

However, there are several ways to increase the reaction rate of a splint smoldering. For example, we can increase the concentration of the initial reagents. This is exactly what happens when we put the splint into the flask filled with almost pure oxygen. The splint is now surrounded by a much higher concentration of oxygen molecules than that found in air. Along with the increase of the temperature, this dramatically speeds up the rate of reaction and the splint ignites with a bright flame.

Where does oxygen come from in the flask?

Oxygen is produced by the decomposition of hydrogen peroxide as shown in the following reaction:

2H2O2 → O2 + 2H2O:

Then, why can regular pharmaceutical grade hydrogen peroxide be stored for a long period of time (up to three years if the bottle remains unopened) without any signs of decomposition? The secret is in the reaction rate. On its own, hydrogen peroxide decomposes very slowly. We can, however, make this reaction proceed faster by using special accelerators known as catalysts. A catalyst significantly speeds up a reaction rate (sometimes even by a factor of several million!).

Why is hydrogen peroxide used to treat wounds?

The antibacterial effect of hydrogen peroxide is based on its decomposition. A fresh wound excretes drops of blood. Blood, in turn, contains compounds that can accelerate the decomposition of hydrogen peroxide. Thus, upon contact with a wound, hydrogen peroxide decomposes and releases bubbles of oxygen. It’s important to understand that this isn’t “regular” oxygen. These are not O2 molecules but rather very active O∙ particles that eliminate any microbes in its presence. Upon collision with each other, these same particles bond together and produce molecular oxygen O2:

2O∙ → O2

Why did we add manganese dioxide MnO2?

Manganese dioxide MnO2 serves as a catalyst in the decomposition of hydrogen peroxide. It significantly speeds up the rate of reaction. When manganese dioxide is added to regular 3% hydrogen peroxide, it starts to hiss and undergo decomposition releasing a considerable amount of oxygen. Within a short time, oxygen completely fills the flask. This allows us to ignite our splint!