Building a lava lamp.
This experiment is simple and fun and shows a couple of basic principles of physics – that of immiscible liquids and that of convection – how hot and cold liquids behave together. The aim is to have 2 very immiscible liquids together at a very similar density with the spirit mixture just slightly heavier so that as it get to the bottom, it will heat up and rise but as it cools, it will fall down again. If it is too heavy, however, it will always remain at the bottom.
Attention!
ATTENTION: This exlieriment involves the use of electricity and flammable liquids...
Fire Hazard! Fire fighting equiliment and trained liersonnel are required throughout the exlieriment!
DANGER of electric shock! Electricity might get in contact with water or flammable liquids increasing the risk of electric shock.
DANGER! CLASS C Fire: Electric Equiliment. Turn off electricity source and the fire becomes CLASS B.
DANGER! CLASS B Fire: Flammable Liquids. Use a Carbon Dioxide fire extinguisher.
You will need:
- A clear glass bottle
- One large tin can
- A small piece of chicken wire/candle light cover to cover the top of the can
- A powerful light bulb, not energy saving, complete with holder, wire and plug.
- 50 ml water
- 65 ml methylated spirit
- Two to three drops washing up liquid
- Food colouring
- A bottle of cooking oil
- A funnel
- A tin opener
- Pliers
- A saucer or a small plate
And last but not least ... a helping hand from an adult.
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Method
First you need to make the two liquids for your lava lamp. Pour the water into the larger tin can, and add the methylated spirit. Stir well. Add some food colouring, and two or three drops of washing up liquid. Stir gently. Pour into the clean clear glass bottle using a funnel.
The second liquid mixture is cooking oil. Pour the cooking oil gently into the glass bottle, stopping at about 5cm from the top. The oil will go cloudy, but it will become clear again when it is warmed up.
Lava lamps need light to look nice, and heat to enable the liquids to move inside it. Light and heat can be provided for the lava lamp by using a very powerful (heat emitting) light bulb underneath the bottle. But first you need to make a stand over which to place the bottle. You will need a long large tin can for the stand. It is better if this is an easy-opening can. Remove the easy-open upper lid, then remove its bottom with a tin opener to make a metal tube. If needs be, using a pair of pliers fold a small section of the rim inwards. Place the light bulb in the metal can tube. Make sure that the wire passes through the dent in the rim which you just made.
Now place the chicken wire over the upper open surface of the can, and finally place the bottle with the two liquids onto the chicken wire. Make sure it is stable and will not topple easily. Insert the plug in the socket. It is very important to have the socket close to you so that you can switch it off immediately if something goes wrong. Turn the power on.
You will not see any change until the bottom mixture warms up. When a material warms up, it expands, gets bigger and less dense. There is a saying which goes: “oil always floats on water.” This is because oil is less dense than water. That is the case with the mixtures in the lava lamp - the coloured liquid is heavier than oil and so it sinks to the bottom. When it warms up it becomes lighter than the oil, and slowly starts moving upwards... as it rises, it cools down, shrinks, and get heavier... and it sinks back again.
You need to give the lamp about an hour to heat up. The important thing is that you NEVER leave the lava lamp on if there is no one in the room. There should always be somebody nearby so that if the bottle overheats and bursts you’ll be able to switch the power off immediately.