Activity Introduction

Quick summary: In this experiment students will participate in or observe a simple experiment to find out whether hot or cold water freezes fastest.

These Snappy Science resources have been created to boost science education in primary schools across Australia. Each lesson is designed to support teachers with the scientific knowledge, ideas and resources to stimulate a sense of wonder and curiosity in their students. Many of the big issues that Australian society will face in the future are around technology, energy, resources and climate change. All of these require students to engage with science – but most of all to enjoy science!

Science at Home: These Snappy Science resources can also be used to engage families in fun science and learning for life. You can download a student friendly version of this activity here and you can also check out the Snappy Science Digital Library.

General capabilities: Critical and creative thinking.

Australian Curriculum content description: This activity is relevant to Science Inquiry Skills across all primary year levels of the Australian Curriculum.

Year 1 Science

  • Everyday materials can be physically changed in a variety of ways (ACSSU018)

Year 3 Science

  • A change of state between solid and liquid can be caused by adding or removing heat (ACSSU046)

Year 5 Science

  • Solids, liquids and gases have different observable properties and behave in different ways (ACSSU077)

Year 6 Science

  • Changes to materials can be reversible, such as melting, freezing, evaporating; or irreversible, such as burning and rusting (ACSSU095)

Syllabus outcomesST1-12MW, ST2-12MW, ST2-7PW, ST3-12MW.

Time required: 5 minutes for explaining activity and putting cups into the freezer, need to check cups every 15 minutes.

Resources required: Foam cup with cold water, foam cup with same amount of very hot tap water, freezer, clock or timer, pen.

Safety advice: This activity requires very hot water – depending on student age and ability this activity may be either a student-led experiment or a teacher-led demonstration.

Keywords: Hot water, cold water, freeze.

Cool Australia’s curriculum team continually reviews and refines our resources to be in line with changes to the Australian Curriculum.


Teacher Worksheet

Brief summary:

Students will participate in or observe a simple experiment to find out whether hot or cold water freezes fastest.

Students can use the Predict, Observe, Explain table on the Student Worksheet to describe and reflect upon this experiment.

You will need:

  • Foam cup with cold water
  • Foam cup with same amount of very hot tap water
  • Freezer
  • Clock or timer
  • Pen

What to do:

Step 1. Take your two foam cups and label one "hot" and the other "cold".

Step 2. Fill one foam cup with cold water and one foam cup with the same amount of very hot tap water.

Step 3. Place the cups in the freezer at the same time and start the timer.

Step 4. Check the cups every fifteen minutes. To the surprise of most the hot water in fact freezes first!

How does it work?

Known as the Mpemba effect - after a Tanzanian student who noticed that hot ice cream mix freezes faster than a cold - it was in fact first observed by Aristotle, then later Francis Bacon and René Descartes. But while

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Student Worksheet

In this experiment you will be experimenting to see whether hot water or cold water freezes the fastest.


Explain what you think will happen:


Explain what happened:


Explain why you think this happened:

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