Heat Quiz

Which reaction is exothermic

A. CH4 + 2O2 mc016-1.jpg CO2 + 2H2O + 891 kJ

An ice cube is placed on a kitchen counter. Which best describes heat flow in this situation?

D. Heat flows from the counter to the ice, causing the molecules in the counter to move more slowly.

How does the potential-energy diagram for a reaction indicate whether the reaction is endothermic or exothermic?

A. An endothermic reaction has reactants that are lower in energy than products because energy is absorbed to form the products.

Two samples of carbon come into contact. Heat will transfer from Sample A to Sample B if the average kinetic energy of Sample A's atoms is________ the average kinetic energy of Sample B's atoms.

A. Greater than.

A student touches a freshly baked cake that was taken out of the oven. Which best explains why the cake feels hot?

B. Molecules in the cake are moving faster than molecules in the skin.

A baker touches a pie right after taking it out of the oven. Which statement best explains why the pie feels hot?

B. Molecules in the pie move faster than molecules in the skin, so heat is transferred to the skin.

The temperature of a sample of liquid water changes from 50°C to 30°C. Which statement best explains the change that must happen at the molecular level?

B. The molecules move more slowly and their average kinetic energy decreases.

Heat that flows by conduction is the transfer of thermal energy between substances in contact. What must occur for this to happen?

C. One system must have higher kinetic energy than the other system.

What is thermal energy?

C. The kinetic energy of particles in a system.

A hot metal plate at 150°C has been placed in air at room temperature. Which event would most likely take place over the next few minutes?

D. The air molecules that are surrounding the metal will speed up, and the molecules in the metal will slow down.

The temperature of a gas is increased. Which statement best explains the effect that this has on the motion of gas particles?

D. The average kinetic energy increases, and the particles collide more frequently.

Two different gases are stored in separate closed containers. If both gases have a temperature of 50°C, which statement is true?

D. The gas molecules in both containers have the same average kinetic energy.