Thermal Energy Review

A chef needs to increase the temperature of a food dish. She thinks she can do this by stacking another dish on top of it. She has three dishes to choose from for the top dish: A, B, and C. Which one of these dishes would make the food dish the warmest when placed on top of it? As part of your answer, explain how the energy and temperature of both the top dish and the food dish will change when the food dish warms up, and why.

How did the temperatures of the four books compare before they touched? How will the temperatures of the two top books compare after the books have been touching for a while, and why?

What happens to the molecules in a computer when the temperature of the computer decreases?

• The energy of the molecules in the computer decreases.

• The energy of the molecules in the computer increases.

• The cold energy of the molecules in the computer increases.

• The computer loses heat molecules.

What happens to the molecules in the ground when the temperature of the ground increases?

• More heat molecules combine with the molecules in the ground.

• The energy of the molecules in the ground decreases.

• The energy of the molecules in the ground increases.

• The cold energy of the molecules in the ground decreases.

After the gears have been touching for a while, which of the two bottom gears will be cooler, and why?

• The smaller bottom gear will be cooler than the larger bottom gear, because less energy has to transfer for the molecules to reach the same temperature as the molecules of the top gear.

• The larger bottom gear will be cooler than the smaller bottom gear, because the energy that transferred to it was spread out over more molecules.

• The larger bottom gear will be cooler than the smaller bottom gear. It started with more total energy, so less energy had to transfer for both gears in Set B to reach the same total energy.

• Both gears will be the same temperature, because both of the top gears had the same amount of energy to transfer and the molecules in the bottom gears start with the same energy.

What happens to the molecules of the rice when the temperature of the rice increases?

• The energy of the molecules in the rice increases.

• The cold energy of the molecules in the rice decreases.

• The energy of the molecules in the rice decreases.

What must be true of the energy of the toast when the energy of the plate increases?

• Its energy stays the same while the energy of the plate increases.

• Its energy decreases while the energy of the plate increases.

• Its energy increases while the energy of the plate increases.

• It is impossible to know without data on the number of molecules in each object.

How does the temperature of the garage bucket compare with the temperature of the outside bucket before the buckets touch? What will happen after the buckets have been touching for a while?

• Before the buckets touch, the two buckets are different temperatures. Once the buckets are touching, both kinetic energy and cold energy will transfer between the molecules of the two buckets until both buckets reach the same temperature, which will be in between their starting temperatures.

• Before the buckets touch, the garage bucket is hotter than the outside bucket. Once the buckets are touching, the cooler outside bucket will gain kinetic energy until the molecules of both buckets have an energy of 18, because hotter things increase the temperature of cooler things.

• Before the buckets touch, the garage bucket is cooler than the outside bucket. Once the buckets are touching, the hotter outside bucket will transfer kinetic energy to the molecules in the cooler garage bucket until both buckets reach the same temperature, which will be in between their starting temperatures.

• Before the buckets touch, the garage bucket is hotter than the outside bucket. Once the buckets are touching, the garage bucket will transfer kinetic energy to the molecules in the cooler outside bucket until both buckets reach the same temperature, which will be in between their starting temperatures.

After the pans have been touching for a while, which of the two bottom pans will be cooler, and why?

• The smaller bottom pan will be cooler than the larger bottom pan, because less energy has to transfer for the molecules to reach the same temperature as the molecules of the top pan.

• The larger bottom pan will be cooler than the smaller bottom pan. It started with more total energy, so less energy had to transfer for both pans to reach the same total energy.

• The larger bottom pan will be cooler than the smaller bottom pan, because the energy that transferred to it will have spread out over more molecules.

• Both pans will be the same temperature because both of the top pans had the same amount of energy to transfer and the molecules in the bottom pans start with the same energy.

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?

• 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 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 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 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.