Key Stage 3: Which mixture makes the best bubble?

Starter

Begin the lesson by using the presentation to play the introduction video. 

Prompt questions (whole class discussion):

• Which bubble do you think is “better”?
• What makes a bubble “good”?
• Is it size? Colour? Shape? How long it lasts?
• Do we all agree, or do different people value different things?

In pairs or small groups, students list 3–4 criteria they could use to judge a “good” bubble. Encourage them to think about:

• Which criteria are observable
• Which are measurable
• Which would be subjective (opinion-based)

Possible student responses may include:

• Size of bubble
• Colour / shininess
• Shape
• How long the bubble lasts before popping

Bring the class back together and challenge students:

• Which of these could we measure accurately?
• Which would be hardest to measure fairly?

Guide students towards the conclusion that:

Bubble lifespan (how long it lasts before popping) is the most objective, measurable and scientific criterion.

Main Teaching

Using the presentation, go through identifying the variables. 

Independent variable (what we change):

• Type of bubble mixture (e.g., different amounts of washing-up liquid, glycerine, sugar, etc.)

Dependent variable (what we measure):

• Time taken for the bubble to pop (bubble lifespan, measured in seconds)

Control variables (what we keep the same):

• Bubble wand size
• Amount of mixture used
• Method of blowing bubbles
• Environment (same room, no fans, same surface)
• Person blowing the bubble (if possible)

Explicitly link this back to fair testing:

If we don’t control these variables, we can’t be confident that the mixture caused the difference.

Students now complete the method section of the planning sheet.

Prompt them to include:

• Step-by-step instructions written clearly enough that another student could follow them
• How the bubble will be produced
• How timing will start and stop
• How the results will be recorded

Circulate and challenge vague language:

“Make a bubble” → How exactly?

“Time it” → Using what? When do you start and stop the timer?

Pause the class and ask:

If one bubble lasts 12 seconds, does that mean the mixture is good?

Introduce the idea of repeats:

• Each mixture should be tested at least 3 times.
• Results should be averaged to improve reliability.
• Students add repeats to their method.

Mission Assignment

Explain the practical safety expectations clearly:

• Bubble solution is not for consumption – no tasting or touching faces.
• Any spills must be wiped up immediately to prevent slips.
• Equipment should be handled calmly to avoid splashing.

Step 1: Setting Up 

Students collect equipment and prepare their first bubble mixture according to their plan.

Remind students:

• Use the same bubble wand each time.
• Produce bubbles in the same location.
• Start timing as soon as the bubble leaves the wand.
• Stop timing the moment the bubble pops.

Step 2: Collecting Results 

Students carry out at least three repeats for each bubble mixture.

They record results clearly in a table, including:

• Mixture tested
• Time taken for each bubble to pop (seconds)
• Any anomalies (e.g., bubble popped immediately due to collision)

Encourage students to: 

• Use a stopwatch correctly
• Read times accurately
• Record results immediately to avoid forgetting or estimating