An electric kettle has a power rating of 2.4kW. How long does it take the kettle to heat up 4.5kg of tap water from 28°C to 100°C ? (c of water = 4200Jkg1°C-) What assumption must you make to arrive the answer ? pls helppp

An insulated thermos contains 148 g of water at 72.7 ˚c. you put in a 11.7 g ice cube at 0.00 ˚c to form a system of ice + original water. the specific heat of liquid water is 4190 j/kg•k; and the heat of fusion of water is 333 kj/kg. what is the net entropy change of the system from then until the system reaches the final (equilibrium) temperature?