Comparing thermal insulation
The hypothesis that sand is able to keep water warm for the longest period of time, compared to air and styrofoam is proven not to be true. Styrofoam actually kept water warm for the longest period of time.
Thermal insulation materials are used to prevent hot or cold objects from losing or gaining heat and having the same temperature as the surrounding environment. The thick sweaters that we use on cold days help keep our bodies warm. The insulating walls in our houses help keep the cool air inside on hot days. The thermos bottle is useful in keeping our drinks and food warm for a longer period.
Try to repeat the experiment using ice cubes instead of boiling water.
The experiment can also be repeated using other insulation materials like cloth, newspaper or saw dust.
Thermal insulation - http://en.wikipedia.org/wiki/Thermal_insulation
Thermal insulation prevents hat from escaping - http://www.school-for-champions.com/science/thermal_insulation.htm