AnswersCR SS Chemistry S2 201819 2026Unit Test

Calorimetry Answers

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1
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An ice cube is placed on a kitchen counter. Which best describes heat flow in this situation?

A
Heat flows from the ice to the counter, causing the molecules in the counter to move more quickly.
B
Heat flows from the ice to the counter, causing the molecules in the counter to move more slowly.
C
Heat flows from the counter to the ice, causing the molecules in the counter to move more quickly.
D
Heat flows from the counter to the ice, causing the molecules in the counter to move more slowly.
2
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Iron reacts with oxygen in a chemical hand-warmer. How should this reaction be categorized?

A
as an exothermic process because it releases heat
B
as an endothermic process because it releases heat
C
as an exothermic process because it absorbs heat
D
as an endothermic process because it absorbs heat
3

Which reaction is exothermic?

A
CH4 + 2O2 CO2 + 2H2O + 891 kJ
Option A
B
NH4NO3 + H2O + 25 kJ NH4+(aq) + NO3-(aq)
Option B
C
2H2O + 286 kJ 2H2 + O2
Option C
D
N2 + O2 + 181 kJ 2NO
Option D
4

Two samples of carbon come into contact. A heat transfer will occur between sample A and sample B. What must be true for heat to transfer from sample A to sample B?

A
The average kinetic energy of A is greater than that of B.
B
The average kinetic energy of B is greater than that of A.
C
The average kinetic energy of both samples is equal.
D
The average kinetic energy does not determine the direction of heat transfer.
5

What is thermal energy?

A
the average overall volume of a system
B
the total number of molecules in a system
C
the kinetic energy of particles in a system
D
the measure of temperature in a system
6

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?

A
Molecules in both the metal and the surrounding air will start moving at lower speeds.
B
Molecules in both the metal and the surrounding air will start moving at higher speeds.
C
The air molecules that are surrounding the metal will slow down, and the molecules in the metal will speed up.
D
The air molecules that are surrounding the metal will speed up, and the molecules in the metal will slow down.
7

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

A
The thermal energies of gas molecules in the two containers are unrelated.
B
The gas molecules in both containers will absorb heat from the surroundings.
C
The molecules in one gas will transfer energy to the molecules in the other gas.
D
The gas molecules in both containers have the same average kinetic energy.
8

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.
B
An endothermic reaction has reactants that are higher in energy than products because energy is released to form the products.
C
An exothermic reaction has reactants that are lower in energy than products because energy is released to form the products.
D
An exothermic reaction has reactants that are higher in energy than products because energy is absorbed to form the products.
9

Which event is endothermic?

A
the burning of a match
B
the change of water vapor to a liquid
C
the combustion of propane gas
D
the melting of ice
10

Which statement about exothermic reactions is accurate?

A
As reactants form products, the potential energy decreases.
B
As reactants form products, the potential energy increases.
C
Thermal energy is transferred from the product to the reacting substances.
D
Thermal energy is transferred from the surroundings to the reacting substances.

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