Thermodynamics Review

Which of the following describes the molecules in a sample of water as the temperature of the water changes from 20°C to 30°C?

• The molecules speed up and their average kinetic energy increases.

• The molecules slow down and their average kinetic energy decreases.

• The molecules speed up and their average kinetic energy stays the same.

• The molecules slow down and their average kinetic energy stays the same.

During evaporation, molecules with higher-than-average kinetic energy escape from the surface of a liquid and enter the gas phase. As a result, the average kinetic energy of the remaining liquid molecules decreases.

Which of the following occurs because of the decrease in the liquid’s average kinetic energy?

• The temperature of the liquid increases.

• The temperature of the liquid decreases.

• The specific heat of the liquid increases.

• The specific heat of the liquid decreases.

The graph shows the temperature of a sample of water as it is heated at a constant rate. Which of the following conclusions is best supported by the information in the graph?

• The water boils between points X and Y and condenses between points Y and Z.

• The average kinetic energy of the water molecules increases between points X and Y and stays the same between points Y and Z.

• The water evaporates between points X and Y and the average kinetic energy of the water molecules increases between points Y and Z.

• The average kinetic energy of the water molecules remains the same between points X and Y and the water boils between points Y and Z.

The temperature of a small metal cube is 75°C. A student places the cube into an insulated container of water at a temperature of 40°C. The student then seals the container. What is the temperature of the water inside the container 10 minutes later?

• below 40°C

• between 40°C and 75°C

• exactly 75°C

• between 75°C and 100°C

Which of the following always occurs when an object at 60°C remains in contact with another object at 10°C in a closed system?

• Heat flows from the 60°C object to the 10°C object until both objects reach 50°C.

• Cold flows from the 10°C object to the 60°C object until both objects reach 50°C.

• Heat flows from the 60°C object to the 10°C object until both objects reach the same temperature.

• Cold flows from the 10°C object to the 60°C object until both objects reach the same temperature.

A small steel rod is placed in 5 L of water. The initial temperature of the steel rod is 120°C, and the initial temperature of the water is 10°C.When does heat stop flowing between the steel rod and the water?

• when the steel rod reaches 65°C

• when the water reaches its boiling point

• when the steel rod reaches 10°C and the water reaches 120°C

• when the steel rod and the water reach the same temperature

A container of water with an initial temperature of 90°C is placed in a room where the temperature is 20°C. Which of the following statements describes what happens to the water over the next several hours?

• The thermal energy of the water decreases, and its temperature decreases to 45°C.

• The thermal energy of the water decreases, and its temperature decreases to 20°C.

• The thermal energy of the water remains constant, and its temperature decreases to 55°C.

• The thermal energy of the water remains constant, and its temperature decreases to 70°C.

In radiation, heat is transferred by which of the following?

• Electromagnetic waves

• Fluid motion

• Mechanical waves

• Particle contact

Which of the following statements describes an advantage of using a wooden spoon instead of a metal spoon to stir a pot of hot soup?

• A wooden spoon radiates heat faster than a metal spoon.

• A wooden spoon has a lower specific heat than a metal spoon.

• A wooden spoon does not conduct heat to its handle as quickly as a metal spoon.

• A wooden spoon lowers the boiling point of the soup, but a metal spoon does not.

Sunlight heats a dark rock. A snake then moves onto the rock in order to increase its body temperature. Which of the following sequences represents how heat energy is transferred from the Sun to the rock to the snake?

• radiation then conduction

• radiation then convection

• conduction then radiation

• convection then radiation