. A plumber is going to put two pipes in a wall, one in front and one in back. The pipes will be touching once they are installed. Both pipes are the same size and have the same number of molecules. The diagram above shows the pipes now, before they have touched. Use the information in the diagram to answer the question.

Question

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?

Responses

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.
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.
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.
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.

Answer 1

To analyze the scenario, let's break down the information provided:

1. We have two pipes that are about to touch, and they have different temperatures before they come into contact.
2. The process of heat transfer involves kinetic energy, which is related to the temperature of the molecules in the pipes.

Given the options presented:

• Option a states that the front pipe is cooler than the back pipe, and when they touch, kinetic energy will transfer from the back pipe to the cooler front pipe until they reach the same temperature.

• Option b mentions that the pipes are at different temperatures but uses the term "cold energy," which is not a standard term in thermodynamics to describe heat transfer.

• Option c asserts that the front pipe is hotter than the back pipe and transfers energy to the cooler pipe until both reach an energy level of 100, which is not correctly overall because it establishes a specific temperature that isn't mentioned earlier.

• Option d also claims the front pipe is hotter than the back pipe and explains that the hotter front pipe will transfer kinetic energy to the cooler back pipe until they reach an equilibrium temperature.

Assuming the scenario you provided indicates that the front pipe is initially cooler than the back pipe (based on choices a & b), option a accurately describes the scenario. Therefore, the best response is:

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.