Lava Lamps

“Mrs Sprague, we should make this lava lamp,” announced Van. “Alright then, write me a shopping list so I can get what we need,” replied Mrs Sprague.

Van wrote his shopping list

Vegetable oil

Water

Salt

Food colouring 

Glitter

Jar and lid

Torch

Room 10 students followed the instructions on the website to make the lava lamp.

“I can’t see anything,” observed Hunter.

“I think I can see some bubbles down the bottom,” encouraged Van.

“Maybe we put too much food colouring in and it’s too dark to see.” reflected Ethan

“Shine the torch at the bottom,” suggested Emma-Lee.

“I’ve seen better lava lamps,” announced William.

Overall, the results of this experiment were underwhelming! There was some slight bubble action down the bottom of the jar, but the reaction was minimal. 

Disappointing as it was, science experiments that don’t work help us learn just as experiments that do work. It’s all part of the scientific process.

So a challenge was set by Mrs Sprague: “Can we find another set of instructions to make a lava lamp that will create a bigger reaction?”

Lava Lamp research took place on Google, and Mrs Sprague brought in a bag of “classroom explosives”: oil, vinegar, baking soda, salt, and Alka-Seltzer tablets. “Hopefully we will have everything we need to make a more exciting lava lamp,” said Morgan.

“Baking soda makes things bubble. Is there a lava lamp with baking soda?” questioned Bonnie.

“ I found instructions that use more oil than water. The first lava lamp used ¾  water and ¼  oil. This one might be better,” suggested Victoria. 

“I read that we should use a light colour for the food colouring, like yellow, and then we will be able to see the reaction better,” recommended Valentina.

“This one uses Alka-Seltzer tablets. I know those tablets make things bubble,” exclaimed Ella.

Two further lava lamps were made in response to the class's research. One with more oil, yellow food colouring, baking soda and vinegar.  The other with more oil, yellow food colouring and an Alka-Seltzer tablet broken into quarters.

“The baking soda and vinegar lava lamp was good; the bubbles were bigger, and there were more of them,” observed Charlie.

“Definitely the lava lamp with the Alka-Seltzer had the best reaction. There were heaps of bubbles,” confirmed William.

“Well, that was a cool experiment, BUT what about the science? Why do baking soda and vinegar or Alka-Seltzer make a better reaction than salt?” probed Mrs Sprague.

Time for more research. What is the actual science behind these experiments? Here is what Room 10 students learnt.

Baking soda and vinegar or Alka-Seltzer work better than salt in the lava lamp experiment because they create a chemical reaction that produces gas (carbon dioxide ) (CO₂) gas bubbles.Salt only causes a temporary disturbance. Salt is denser than oil, so it sinks to the bottom, carrying some water with it. As the salt dissolves, the water drops separate and float back up. But there’s no gas involved, so it doesn’t keep the motion going. The effect is brief and much weaker than with Alka-Seltzer or the baking soda and vinegar.

Next steps

William would like to investigate if the temperature of the water and oil  (hot or cold) affects the reaction in the lava lamp. “I think we could get an even better reaction if the oil and water are warm because I think warm things react better than cold.” William