A sleeve made of a poor conductor can slow heat transfer through a cup’s sides. Warm water loses heat to the cooler room more slowly. Cold water gains heat from the warmer room more slowly.
Start by comparing the water temperature with the room temperature. Heat moves from the warmer place to the cooler one. The sleeve slows that transfer in either case.
- Identify what is warmer, the water or the room.
- State the direction of heat transfer.
- Compare each sleeved cup with an otherwise similar bare cup.
Worked example | Compare four cups in one room
In a room at 25°C, two identical cups start with water at 70°C. One has a sleeve. Two other matching cups start with water at 10°C, again with a sleeve on just one. Each comparison uses the same amount of water and the same observation time.
In this set of example readings, the sleeved warm cup reaches 62°C and the bare warm cup reaches 55°C. The sleeved cold cup reaches 14°C and the bare cold cup reaches 18°C. The water in each sleeved cup changes temperature by a smaller amount than the water in its matching bare cup.
Explain each pair using the temperature difference
The warm water starts above room temperature, so it loses heat. The cold water starts below room temperature, so it gains heat. In both pairs the sleeve slows transfer through the cup’s sides.
In a fair comparison, keep the lids, cup material, water amount and observation time the same within each pair. Heat can still transfer through other parts of the cup.
Spot a second change
A pupil puts a lid on the sleeved cold cup but leaves the bare cold cup uncovered. Why is this a less fair test of the sleeve?
Answer. The lid can also affect heat transfer. With both the sleeve and lid changed, the temperature readings cannot isolate the effect of the sleeve.
Frequently asked questions
Does the sleeve warm up cold water?
The surroundings are the source of the heat gained by the water. The sleeve slows that gain through the sides.
Why use the same amount of water?
A different amount of water can change how much its temperature rises or falls for the same energy transfer.
Official information
MOE, 2023 Primary Science Teaching and Learning Syllabus, Primary Four Energy Forms and Uses (Heat), heat transfer and conductors. Syllabus checked 12 November 2026. The examples are original.