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I do love a lava lamp, they are so hypnotic to watch, no wonder you often find them in sensory rooms. There have been pins out there for ages showing you how to make them, so as EC said he wanted to do more science based activities I thought now would be a great time to test them out.
We have been testing 2 different types of lava lamps; both of them require the same items to make the base. However one needs a dissolvable tablet, like Alka-Seltzers, while the other one needs salt to make it work.
You will need:
- Glass or empty bottle
- Food colouring
- Alka-Seltzers or another dissolvable tablet
* We tried using both cooking oil and baby oil. There really isn’t much difference in the outcome. The baby oil just means that you have a clear coloured layer of oil.
Lava lamp using Alka-Seltkers
Fill a quarter of your glass or empty bottle with water.
Next add some food colouring.
Fill the rest of glass/bottle up with oil. Make sure that you leave about an inch at the top for the gas to escape.
Finally add your tablets and watch your lava lamp begin to move. Just like a real one, it starts out kind of slow and then gets quicker and quicker. Keep adding more tablets to it to if it looks like it is running out of steam.
If you have made this in a bottle just add the lid once you have finished with it and store it until you want to bring it out again. It should last a few weeks.
Science behind it
Once the tablet hits the water it begins to release gas bubbles. This reaction is the same as the bicarbonate of soda and vinegar experiments. As the gas has a lower density than the surrounding layers it rises to the surface, taking some of the coloured water with it. Once it has reached the surface the gas is released and the coloured water sinks back to the bottom.
Lava lamp using salt
This time when you are making it you will want to add more water than oil to your glass/bottle.
Don’t forget to add your food colouring as well.
This time instead of adding Alka-Seltkers to it use salt. EC added a couple of pinches to begin with, but ended up putting handfuls in by the end.
Science behind it
This lava lamp is the opposite of the previous one. Now the salt is heavier than both the oil and the water and therefore sinks to the bottom. As it sinks it carries the oil with it. Once it has dissolved the oil rises back up to the surface.
This science experiment was a total hit with both of them. They preferred the first lava lamp, mainly because they loved it fizzing up. By the end our ones looked like some sort of Harry Potter potions class. But they did agree that the salt lava lamp looked more like a real one with its slow moving bubbles.
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