Which Wrap Slows Melting? A Class 8 Ice Investigation

In this guide

A wrapped piece of ice can look as though it has been given a blanket. Does the blanket make it warm, or help it remain frozen? Turn that everyday puzzle into a Class 8 investigation where learners plan the comparison, measure a change and resist claiming more than their evidence allows.

Choose the thing you will actually measure

Ask:“After the same time in our classroom, which wrap design leaves the most ice? ” The measured outcome is the approximate mass of ice remaining, not the ice’s temperature. Melting can absorb energy without producing the same sort of temperature rise that occurs when liquid water warms. Avoid calling this a race to see which ice is “coldest”.

The American Chemical Society’s ice-and-insulation activity provides a useful primary starting point: compare insulated and uninsulated containers with similar starting ice. The procedure below is an original classroom extension that adds explicit controls, repeated trials and a complete practice dataset.

Prepare three comparable wrap designs

• Control:an identical cup with its matching lid and no outer wrap.
• Paper design:one 20-by-20 cm sheet of newspaper folded around the sides and base, secured with one reusable band.
• Cotton design:one 20-by-20 cm square of clean cotton fabric wrapped around the sides and base, secured similarly.
• Make two cups of each design. Keep the lids alike and leave the top uncovered in every case. Put a matching band on the control cups too.

These are comparisons of complete wrap designs. Newspaper and fabric may differ in thickness, folding and trapped air even when the sheet dimensions match. Do not describe the result as a perfect measurement of the materials’ intrinsic insulating properties. Ask groups to sketch the wrap, so another group could reproduce the design.

An adult supplies ice from one batch and weighs approximately 30 grams into each cup, using the same small scale. Record the actual starting mass; do not silently write 30 if the scale shows 29. Equal-sized cubes from one tray can support a qualitative version when a scale is unavailable, but that version cannot produce gram measurements.

Keep a clock beside the plan

Use 5 minutes for the question, 8 for checking the setup, 25 for the timed comparison, and 7 for the conclusion. During the waiting period, learners prepare their records, draw a heat-transfer explanation and analyse the practice data below. The teacher pilots the timing before class; if little melting occurs, continue observations later rather than forcing a result.

• Keep all cups on the same tray, in shade and away from a strong draught or heat source. Keep the cup type, lid, starting ice, elapsed time and handling method alike.
• Start cups at short, recorded intervals if one scale must serve the whole class. Measure each cup after its own 25-minute interval. Do not give the last cup extra test time.
• At the endpoint, the adult uses a spoon and strainer to lift the remaining ice, lets it drain for the same 5 seconds, then weighs it in the same dry, tared container. Work promptly and record the approximate gram reading.
• Use the second cup of each wrap as a repeat. Record both readings rather than choosing the more attractive one. Consider different tray positions or handling delays as possible sources of variation.

Do not eat the ice or drink the meltwater. Avoid prolonged skin contact with ice; an adult handles the weighing. Wipe spills immediately, wash hands afterwards, and use seated observer or recorder roles where needed. Large labels, spoken readings and a partner recording numbers make the inquiry accessible without making handling speed part of the assessment.

Use a record with room for the calculation

Copy a row for each real cup: wrap design; trial number; starting ice mass; time started; time measured; ice remaining; mass melted; unusual events. Calculate mass melted = starting mass – remaining ice mass. If both trials started differently, compare the recorded changes and explain the limitation instead of comparing only the final masses.

The table below is invented practice data, with every cup starting at 30 grams and measured after 25 minutes. It is a reasoning exercise, not an expected result or a report of a real school experiment.

Wrap design	Trial	Ice remaining(g)	Mass melted(g)
No wrap	1	8	___
No wrap	2	10	___
Paper	1	15	___
Paper	2	17	___
Cotton	1	19	___
Cotton	2	21	___

Ask pairs to complete the last column, then explain which evidence would answer the original question. They can compare the two readings directly before calculating a mean. A mean summarises these readings; it does not remove an unfair setup or make two trials enough to settle every classroom condition.

Teacher check: calculations and a bounded conclusion

Masses melted are 22, 20, 15, 13, 11 and 9 grams. Mean remaining masses are 9 grams for no wrap, 16 for paper and 20 for cotton. Mean melted masses are 21, 14 and 10 grams respectively. Cotton leaves more ice in both practice trials, so this design slows melting most in this dataset.

A sound conclusion is: “With these wrap designs and this procedure, the cotton-wrapped cups retained more ice after 25 minutes.” It is not: “Cotton is always the best insulator.” Different thicknesses, air gaps, moisture, containers or surroundings could change a comparison. Unequal starting ice or unequal timing would weaken the claim.

Explain where the energy comes from

In a warmer classroom, net thermal energy transfers from the surroundings toward the colder ice. A useful wrap slows that transfer; it does not manufacture cold or stop energy transfer forever. This trial also cannot identify exactly how much energy travelled by conduction, convection or radiation: the whole container-and-wrap arrangement is being tested.

End with an individual three-line response:Our claim…; two pieces of evidence…; one improvement before repeating… Look for evidence drawn from both trials, correct units and a limitation that affects the method. The site’s task-and-rubric guide can help make those criteria visible.

Compare this fair-test habit with the shadow investigation. For another primary procedure, see the ACS Milli’s Insulation Investigation. Keep the next question manageable: repeat one design more carefully before changing several features at once.

AI assistance was used to finalize this contribution. The views expressed are personal views of the author; official statements are identified through linked official sources.