Rocket fuel

Ignite your own rocket fuel!

Difficulty:
Danger:
Duration:
20 minutes
Rocket fuel

Reagents

Safety

  • Put on protective gloves and eyewear.
  • Conduct the experiment on the plastic tray.
  • Keep hair and flammable objects away from flame.
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

It’s been fifteen minutes, and the mixture is still liquid, not ignited, or burning very slowly.

If you’re performing the experiment in a drafty area, it may take more than fifteen minutes to remove the water from the mixture. Wait until the mixture stops boiling (it should solidify). You can also cover the candle holder with foil to speed up the process.

Why isn’t the dry mixture catching fire?

The mixture may not ignite immediately; try holding the wooden stick to it for 3-5 seconds.

I can’t get the Ca(NO3)2 out of the bottle.

This does happen sometimes. Use a wooden stick to loosen the Ca(NO3)2 in the bottle.

Step-by-step instructions

Prepare a mixture of an oxidant Ca(NO3)2 and a fuel K4[Fe(CN)6].

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The crystals of both compounds contain some water molecules. Heat the mixture to make this water evaporate.

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Extinguish the candle when the mixture is completely dry.

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Ignite the mixture.

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Disposal

Dispose of solid waste along with household garbage.

Scientific description

When burning something, you usually care only about the fuel you’re using, whether it be wood, candle wax, or coal. Any burning, however, requires two ingredients: a fuel and an oxidant. An oxidant is a substance that wants to take electrons from the fuel, which is eager to give these same electrons away. Usually, the acting oxidant is the oxygen  in the air, but if you want your fuel to burn without air, you have to include your own oxidant too. This is how space rockets work.

Nitrates such as the calcium nitrate Ca(NO3)2 that we used in our experiment are convenient oxidants because they are solid and easy to store. As potassium ferrocyanide K4[Fe(CN)6] doesn't burn very well in air, it is not often used as a fuel, but in combination with a nitrate it makes a decent fuel for small model rockets and fireworks.

Choosing a good oxidant-fuel pair for a rocket is pretty tricky. You need to be able to store and transport both ingredients, make them react energetically (but not energetically enough to explode!), and take many other factors into account. The principle is always the same: an oxidant takes electrons from a fuel with a release of energy.