A student performs a combustion experiment by burning a mixture of fuel and oxygen in a constant-volume metal can surround by a water bath. During the experiment the temperature of the water is observed to rise. Regard the mixture of fuel and oxygen as the system.
(a) Has heat been transferred? How can you tell?
(b) Has work been done? How can you tell?
(c) What is the sign of Δ U? How can you tell?