Chemistry 2 - Heat
An ice cube is placed on a kitchen counter. Which best describes heat flow in this situation?
Heat flows from the counter to the ice, causing the molecules in the counter to move more slowly.
A baker touches a pie right after taking it out of the oven. Which statement best explains why the pie feels hot?
Molecules in the pie move faster than molecules in the skin, so heat is transferred to the skin.
Heat that flows by conduction is the transfer of thermal energy between substances in contact. What must occur for this to happen?
One system must have higher kinetic energy than the other system.
The temperature of a gas is increased. Which statement best explains the effect that this has on the motion of gas particles?
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?
The gas molecules in both containers have the same average kinetic energy.
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?
The molecules move more slowly and their average kinetic energy decreases.
conduction
a heat transfer that involves direct contact between two substances so there can be collisions between molecules
Iron reacts with oxygen in a chemical hand-warmer. How should this reaction be categorized?
as an exothermic process because it releases heat
endothermic
describing a process that involves the absorption of energy from the surroundings by substances undergoing change
exothermic
describing a process that involves the release of energy into the surroundings by substances undergoing change
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.
greater than
thermal energy
the kinetic energies of the molecules making up a substance; energy that can flow as heat
What is thermal energy?
the kinetic energy of particles in a system
temperature
the measure of the average kinetic energy of the molecules making up a substance
Which event is endothermic?
the melting of ice
heat
the transfer of kinetic energy between molecules as faster-moving molecules collide with slower-moving molecules; energy that flows from a warmer object or substance to a cooler object or substance