First place a small beaker placed inside a larger beaker
Then use a kettle to boil some water and transfer 80cm into the small beaker
Then use cardboard as a lid with a hole
Place thermometer through hole
Record starting temperature
Start a stopwatch
Record temperature every 3 minutes for 15 minutes
Repeat but use an insulating material to fill gap between beakers using same mass of material
This practical could also be done with varying the amount of layers of insulation rather than the material