For the following processes, calculate the change in internal energy of the system and determine whether the process is endothermic or exothermic:
(a) A balloon is heated by adding 850 J of heat. It expands, doing 382 J of work on the atmosphere.
(b) A 50-g sample of water is cooled from 30 degrees Celcius to 15 degrees Celcius, thereby losing approximately 3140 J of heat.
(c) A chemical reaction releases 6.47 kJ of heat and does no work on the surroundings