This experiment demonstrates how a substance can change from a liquid to a gas in an instant! A cup of hot water will immediately explode when a small amount of a very cold alcohol based substance is added. Great care must be taken when performing this experiment, and the cold liquid should be added remotely or from behind a safety screen.
As soon as the liquid is added the entire cup of water will explode launching hot water and probably the cup into the air, so it is important to wear safety goggles and to be a good distance away when it happens.
The liquid is an alcohol based aerosol called 'Tetrafluorethane Dimethyl ether'. The 'Dimethyl ether' part is an organic compound used as propellant in other aerosols and is used with propane for cryogenic freezing.
This substance is found in aerosol cans in DIY or electronics shops but its expensive at around £10. It is commonly used for rapidly cooling electronic parts, removing chewing gum, or for freezing water in pipes that need to be cut. In the shops it can usually be found under the name "Freezer Spray".
How it's Done
The freezer spray is designed to evaporate rapidly as it is sprayed onto a surface as this draws heat away from it very quickly. For this experiment the freezer spray must be collected in liquid form before it can be used.
This is done by holding the nozzle in the plastic lid or similar container like shown on the left. The button is then pressed lightly so that the spray starts to come out slowly and collect in the lid. The first bit of liquid will probably evaporate quickly, but as the lid cools down it becomes easier to collect. The amount to collect will depend upon how big the cup of water is and how long it takes to go from collection to adding it to the water.
Once the liquid is collected it is tipped into a cup of hot water at a distance. It is important that the collected freezer fluid is tipped in at once and not dripped in. If it is added too slowly it will just evaporate before any violent reaction can occur.
Sometimes only fizzing and sputtering occurs, but when done correctly the reaction is immediate and quite powerful.
Important Safety Notes
- The water needs to be hot but not boiling or hot enough to scald.
- The cup holding the hot water should be a light weight plastic type like those from a vending machine.
- The freezer spray should be added to the water away from people, animals, or anything else that would be damaged by hot water.
- The spray should be used outdoors in a well ventilated area away from sources of ignition.
- Safety goggles, gloves and other protective gear are recommended to avoid injury from spilling or splashing of the collected freezer spray.