Science and Technology K–6 · Year 3

Chocolate, butter, wax and ice: different solids melt at different temperatures

Science understanding: Chemical sciences

PracticalLow risk

The idea

Each solid changes to a liquid at its own temperature, so a warm-water bath with a thermometer lets a learner read off the melting temperature of several everyday materials.

Safety card

Low riskAn adult supervises

Hazards

water at 70 degrees Celsius for the wax step
milk chocolate and butter are milk allergens, and milk chocolate may carry nut traces (check the label)

Controls

teacher handles the hot bath
no eating the samples
tongs for the bags
check allergy records before the lesson; learners with a milk or nut allergy observe without handling the chocolate and butter bags

Note

Hot water above 50 degrees Celsius is poured by the teacher. Risk assessment before the lesson using the NSW Department of Education Chemical Safety in Schools package (CSIS 1.7 Risk Assessment) or Primary RiskAssess.

What you need

4 bowls of water: cold at about 10 degrees Celsius, warm at 30 and at 40 degrees Celsius (mixed and checked with the thermometer), and hot at 70 degrees Celsius for the teacher-only wax step
4 small zip bags or foil cups holding: an ice chip (kept in the freezer until step 2), a 5 g piece of milk chocolate, a 5 g piece of butter, a 5 g shaving of paraffin candle wax
digital probe thermometer
timer
tongs

How to do it

Read the room temperature. Note which of the chocolate, butter and wax are already liquid at room temperature (none should be); the ice chip stays in the freezer until step 2.
Float the four samples in their bags on cold water at about 10 degrees Celsius. Record which melt (only ice does).
Move the bags to water at 30 degrees Celsius and wait 3 minutes. Record which have melted.
Move the bags to water at 40 degrees Celsius and wait 3 minutes. Record again.
Teacher moves the wax alone to water at 70 degrees Celsius and shows the class when it melts.
Build a table of material against melting bracket, then order the four materials from lowest to highest melting temperature.
Let the samples cool and record which turn solid again.

What you should see

Ice melts at 0 degrees Celsius, so it melts in the 10 degree bath. Milk chocolate softens and melts at about 30 to 34 degrees Celsius (cocoa butter) and butter at about 32 to 35 degrees Celsius, so both melt in the 30 to 40 degree bracket; their ranges overlap, so these brackets cannot put one ahead of the other. Paraffin candle wax stays solid at 40 and melts in the 70 degree bath (paraffin wax melts at about 46 to 68 degrees Celsius depending on the blend). The ordering ice, then chocolate and butter together, then wax is the result, and each sample turns solid again as it cools: melting is reversible.

What changes

What you change: water bath temperature
What you measure: whether each sample has melted after 3 minutes
What you keep the same: sample mass
time in each bath
bag type

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

All solids melt at the same temperature.
Butter and chocolate are not real solids because they are soft.
Once melted, wax is not wax any more (it solidifies unchanged).

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Science and Technology K-6 Syllabus (2017), current, taught until 2026; code read from the syllabus document on 22 September 2026ST2-6MW-S ST2-1WS-S
Science and Technology K-6 Syllabus (2024), implemented from 2027; NESA's timeline is 2026 plan and prepare and 2027 start teaching, and schools may choose to implement it during 2026; code read from the outcomes page on 22 September 2026ST2-DAT-01
Australian Curriculum v9AC9S3U04AC9S3I03AC9S3I04

Sources

The pages the author read to write this activity.

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