Wrap it in several layers and then place the wrapped cube back in the freezer. Now do the same with other cubes, but using the different materials you've chosen. When all the cubes are ready, take them out of the freezer and place them in a basin. Watch the wrapped cubes, observe the changes and note them in a notebook. After 10 minutes, unwrap the cubes, and note which has melted least.
Re-wrap the cubes and check again every five minutes, until the last cube is melted.