PSLE Science Heat Transfer Question – Balloon Shrinking Explained (2012 Q16)

Introduction

Why does a balloon shrink after being placed in a refrigerator?
This PSLE Science heat transfer balloon question tests whether students understand heat movement, not air leakage or balloon material changes.

Let’s walk through the teacher’s exact board explanation step by step.

The Question

A balloon is blown with air and tied tightly.
After leaving the balloon in the refrigerator for a few hours, the balloon becomes smaller.

Which of the following is correct?
Heat flowed from the…

Step-by-Step Explanation (Teacher’s Working)

Step 1: Observe what happens

• The balloon becomes smaller
• The balloon is placed in a cold environment (refrigerator)

Step 2: Understand heat transfer

• Heat always flows from warmer objects to cooler surroundings
• The air inside the balloon is initially warmer
• The refrigerator air is cooler

Step 3: Identify direction of heat flow

✔ Heat moves from the air inside the balloon
✔ Heat transfers to the surrounding air in the refrigerator

Step 4: Effect on the balloon

• Loss of heat causes the air particles to move slower
• Air contracts
• Balloon becomes smaller

✅ Correct Answer

Heat flowed from the air inside the balloon to the surrounding air

🎯 This matches the teacher’s annotation:
“Gets transferred to the surrounding air”

Key Science Concepts

Common Mistakes Students Make

❌ Thinking air escaped from the balloon
❌ Saying the balloon material shrank
❌ Confusing heat with cold
❌ Choosing the refrigerator as the heat source

Tips for PSLE Students

✔ Always identify hot vs cold objects
✔ Remember heat flows out, not cold flows in
✔ Look for cause → effect relationships
✔ Ignore distractions like balloon material

For Parents

This PSLE Science heat transfer balloon question checks:

• Understanding of energy flow
• Ability to apply scientific principles
• Logical reasoning

Strong conceptual clarity prevents careless MCQ errors.