Which drink makes the best bubbles

Like most children, if given a straw, my four will blow bubbles till the cup overflows, which gave me an idea for a fun investigation. We tried to find out which of three different drinks made the best bubbles, using it as a fun exercise in experimental design.

Bubbly Drinks Challenge

Find out whether purple grape juice, apple juice or chocolate milk makes the most bubbles when you blow into them with a straw.

Things to think about

What will you change?

The drinks

What will you keep the same?

The type of straw
The length of time you blow into the drink
The amount of drink
The same container for each drink
The person blowing - why do we have to think about this?

Method

Measure the same amount of each drink into each container
Blow into each for a set period of time, we chose 10 seconds
Observe the bubbles

Results

We found the milk bubbled up the most, and the juice bubbles popped sooner. Can you think why this might be?

It's most likely to do with surface tension.

Milk contains long, string-like molecules of protein that reduce the surface tension of the bubble, making the bubbles last longer. Simple water molecules stick to each other strongly, they have a high surface tension so the bubbles pop quickly when they are stretched out.

What improvements would you make to your design?

We test plain water as well, and maybe a fizzy drink.

Extension activities

What happens if you use different containers or a wider/thinner straw?

Could you compare low-fat with full-fat milk? How would the fat affect surface tension?

What if the milk was warm?

More science for kids

I've got lots more spooky science experiments and Halloween STEM challenges you might like too!

This activity is great for

Learning Objectives - Key Stage 1 - Science

asking simple questions and recognising that they can be answered in different ways
observing closely, using simple equipment
performing simple tests
using their observations and ideas to suggest answers to questions
gathering and recording data to help in answering questions

Working Scientifically - Key Stage 2 - Science

asking relevant questions and using different types of scientific enquiries to answer them
setting up simple practical enquiries, comparative and fair tests
making systematic and careful observations a
gathering, recording and presenting data
reporting on findings from enquiries
using results to draw simple conclusions, suggest improvements and raise further questions
using straightforward scientific evidence to answer questions or to support their findings.