Thermal Energy Practice Questions

Jaiveon pours some hot tea into a cup. When he puts the tea in the cup, the energy of the cup increases. What must be true of the energy of the tea?

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

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

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

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

Kayla puts a hockey puck onto ice. After a while the temperature of the hockey puck decreases. What happens to the molecules of the hockey puck when the temperature of the puck decreases?

• The hockey puck loses heat molecules.

• The energy of the molecules in the hockey puck decreases.

• The energy of the molecules in the hockey puck increases.

• The cold energy of the molecules in the hockey puck increases.

Kamauri is stacking some cups. The diagram above shows the cups before they touch each other. Use the information in the diagram to answer the question.

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

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

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

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

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

How does the temperature of the bottom chair compare with the temperature of the top chair before the chairs touch? What will happen after the chairs have been touching for a while?

• Before the chairs touch, the bottom chair is cooler than the top chair. Once the chairs are touching, the top chair will transfer kinetic energy to the molecules in the cooler bottom chair until both chairs reach the same temperature, which will be in between their starting temperatures.

• Before the chairs touch, the bottom chair is hotter than the top chair. Once the chairs are touching, the bottom chair will transfer kinetic energy to the molecules in the cooler top chair until both chairs reach the same temperature, which will be in between their starting temperatures.

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

• Before the chairs touch, the bottom chair is hotter than the top chair. Once the chairs are touching, the cooler top chair will gain kinetic energy until the molecules in both chairs have an energy of 35, because hotter things increase the temperature of cooler things.

Kevin put some juice in the freezer. By lunchtime, he took the juice out on a table and the temperature of his juice had increased. What is the difference between the molecules of the juice in the freezer and the molecules of the soup when on the table?

• The molecules of the juice on the table are moving and the molecules of the juice in the freezer are not moving.

• The molecules of the juice on the table are moving faster than the molecules of the juice in the freezer.

• There is no difference because all of the juice is made of the same type of molecules.

• The molecules of the juice in the freezer are smaller than the molecules of the juice on the table.

Jourdyn is making herself some soup. What happens to the molecules in a soup when the temperature of the soup decreases?

• The energy of the molecules in the soup decreases.

• The energy of the molecules in the soup increases.

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

• The soup loses heat molecules.