Question

Ice cubes put inside a thermocol box do not melt fast.Why?

Answer 1

Thermocol box is made up of polystyrene ,a kind of synthetic plastic which is a bad conductor of heat.
Hence prevents the flow of heat from surrounding air entering into box.
As it acts as insulator for transmission of heat, Ice kept in thermocol does not melt fast and retains coolness for longer time.

Answer 2

Thermocol act as a heat insulators  . it isolate  the environment between  both hence ice cube  melts slowly . Tharmocol do not let conduct the heat inside  the box so  temperature remains constant for  longer time in  the box  & ice do not melt fast .