Hypothesis

Sally tells me that when you drop certain small objects into a bottle of fizzy drink, they rise to the top and fall again, over and over, like the bubbles in a lava lamp. The question is, what kind of objects do this?

So, there are two parts to this experiment. The first part involves working out which objects work and which don’t. The second part uses what you’ve found out to create the best ‘lava lamp’ effect possible.

Begin by looking at the equipment list and part one of the method below, then write down what you think will happen. This will be the idea you will test – your ‘hypothesis’.

Here are some ideas to get you thinking:

1. Smooth light objects will rise and fall best when you put them in a glass of fizzy drink.

2.Wrinkled light objects will rise and fall best when you put them in a glass of fizzy drink.

3. Smooth heavy objects will rise and fall best when you put them in a glass of fizzy drink.

4. Some other idea you’ve thought of yourself!

Equipment

You will need:

1. Two fresh bottles of clear fizzy drink (eg lemonade, soda water or tonic water – the cheapest will do)

2. Small, light wrinkled objects (eg sultanas, currants. raisins)

3. Small, light smooth objects (eg fresh sultana grapes, blue berries, black or red currants)

4. Small, heavy smooth objects (eg marbles)

5. Any other small objects you think might be worth testing. Personally, I’m curious to know if lego people would work, or almonds, or dried pasta, or brazil nuts… the testing options are endless! (Please discuss your ideas with an adult to make sure it is something they are happy for you to try.)

6. As many clear drinking glasses as you have groups of objects to test. (eg 1 glass to test sultanas, 1 glass to test blue berries etc)

Method

Part One – Testing Your Hypothesis

1. Set your glasses in line on a table or bench top.

2. Fill each glass with fizzy drink from one of the bottles.

3. Drop two or three objects from each group into separate glasses (eg 3 sultanas in one glass, 3 grapes in the next, and so on)

4. Observe what happens and note down your results.

Part Two – Using Your Results to Make Your ‘Lava Lamp’

1. Open the second bottle of fizzy drink.

2. Drop in a few of the objects that worked best.

3. Sit back and enjoy the effect! (You might like to time how long it takes for the effect to finish.)

Results and Conclusion

When you’ve done the experiment and found out if your hypothesis was correct or not, feel free to share your results – what happened – and your conclusions – what you found out – by telling us what happened in the comment box below.

Contributing Scientist: Sally T

Want to Know How This Works?

Once you’ve finished, take a look at this video, but …

FOR MAXIMUM FUN, don’t look until after you’ve done the experiment. Experiments are always more fun when you get to discover things on your own first. Maybe you will even be able to guess why it works before you see this!

Dr Helen Czerski, author of Storm in a Teacup, explains how bubble physics helps create a lava lamp effect in lemonade bottles. And it even has a link to how the Titanic sank.