How does the temperature of the front pipe compare with the temperature of the back pipe before the pipes touch? What will happen after the pipes have been touching for a while?
a) Before the pipes touch, the front pipe is cooler than the back pipe. Once the pipes are touching, the back pipe will transfer kinetic energy to the molecules in the cooler front pipe until both pipes reach the same temperature, which will be in between their starting temperatures.
b) Before the pipes touch, the two pipes are different temperatures. Once the pipes are touching, the kinetic energy and cold energy will transfer between the molecules in the two pipes until both pipes reach the same temperature, which will be in between their starting temperatures.
c) Before the pipes touch, the front pipe is hotter than the back pipe. Once the pipes are touching, the cooler back pipe will gain kinetic energy until the molecules in both pipes have an energy of 100, because hotter things increase the temperature of cooler things.
d) Before the pipes touch, the front pipe is hotter than the back pipe. Once the pipes are touching, the front pipe will transfer kinetic energy to the molecules in the cooler back pipe until both pipes reach the same temperature, which will be in between their starting temperatures.