I am doing a zainy experiment at home. I need to devise a way of applying a cooling intensity factor (CIF) of around 70 mW/cm2. I need to cool material that is roughly 30 degrees Celsius down to around 2 degrees Celsius. The cooling has to last for a period of one hour or more. The surface area of the cooling devise has to be around 100 cm2. The only equipment that I have at my disposal is a household freezer. My plan is to place some sort of materials in the freezer, cool them down and then apply them to the target. Should I use: (A) Water in a plastic container? (B) Water in a metal container? (C) Lead plate covered in plastic? (D) Lead plate inside a metal container? (E) Some other household materials or a totally different method? Please help. I have the attitude of a mad scientist, but struggle with algebraic concepts like thermal capacity and conduction.