You want to heat 1 L of water by 10 ºC, and you have the following four methods under consideration:
a) You can heat it with a mechanical egg beater that is powered by a 1 kg mass on a rope over a pulley. How far does the mass have to descend to supply enough work for heating the water?
b) You can send the water through a solar collector that has an area of 1 m2. How long (in minutes) will it take to heat the water if the sun's intensity on the collector is 4 J cm-2 min-1?
c) You can heat it with a charcoal fire. The heat of combustion of graphite (MW = 12 g/mol) is -393 kJ mol-1. How many grams of charcoal will have to burn to supply the heat?
d) How many 500 nm photons are required to heat the water?