Exothermic and Endothermic Reactions Quiz

Which of the following is an example of an exothermic process?

• Melting ice

• Combustion of gasoline

• Evaporation of water

• Photosynthesis

Answer explanation

The combustion of gasoline is an exothermic process because it releases energy in the form of heat and light. In contrast, melting ice, evaporation of water, and photosynthesis are endothermic processes that absorb energy.

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DOK Level 1: Recall

What is the primary characteristic of an endothermic reaction?

• It releases energy in the form of heat.

• It absorbs energy from the surroundings.

• It occurs spontaneously.

• It produces light.

Answer explanation

The primary characteristic of an endothermic reaction is that it absorbs energy from the surroundings, leading to a decrease in temperature in the environment. This distinguishes it from exothermic reactions, which release energy.

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DOK Level 1: Recall

• Endothermic

• Exothermic

• Neither

• Cannot be determined

Answer explanation

The reaction releases 572 J of energy, indicating that it is exothermic. In exothermic reactions, energy is released to the surroundings, which is consistent with the given thermochemical equation.

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DOK Level 2: Skill/Concept

Which of the following reactions is endothermic?

Answer explanation

The reaction 6CO2(g) + 6H2O(l) + energy → C6H12O6(s) + 6O2(g) is endothermic because it requires energy input to proceed, as indicated by the 'energy' term on the reactant side.

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DOK Level 2: Skill/Concept

Identify the process that is exothermic.

• Boiling water

• Freezing water

• Photosynthesis

• Melting wax

Answer explanation

Freezing water is an exothermic process because it releases heat to the surroundings as water transitions from liquid to solid. In contrast, boiling water, photosynthesis, and melting wax are endothermic processes that absorb heat.

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DOK Level 1: Recall

In a chemical reaction, if the energy of the products is lower than the energy of the reactants, the reaction is:

• Endothermic

• Exothermic

• Isothermal

• Adiabatic

Answer explanation

In an exothermic reaction, the products have lower energy than the reactants, releasing energy, often as heat. This is the opposite of an endothermic reaction, where energy is absorbed.

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DOK Level 1: Recall

• It is endothermic and absorbs 250 J.

• It is exothermic and releases 250 J.

• It is endothermic and releases 250 J.

• It is exothermic and absorbs 250 J.

Answer explanation

The reaction shows products with energy released (250 J), indicating it is exothermic. Thus, it releases 250 J, confirming the correct choice is that it is exothermic and releases 250 J.

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DOK Level 2: Skill/Concept

Which of the following statements is true for an exothermic reaction?

• The reaction absorbs heat.

• The reaction requires continuous energy input.

Answer explanation

In an exothermic reaction, energy is released to the surroundings, resulting in a negative enthalpy change (\Delta H). This means the correct statement is that the enthalpy change is negative.

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DOK Level 2: Skill/Concept

Which of the following statements is true for an endothermic reaction?

• The reaction absorbs heat.

• The reaction requires continuous energy input.

Answer explanation

In an endothermic reaction, the system absorbs heat from the surroundings, resulting in a positive enthalpy change (\Delta H). This means that energy is required for the reaction to proceed.

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DOK Level 2: Skill/Concept

What type of energy change occurs when ammonium nitrate dissolves in water and the solution becomes cold?

• Exothermic

• Endothermic

• Isothermal

• Adiabatic

Answer explanation

When ammonium nitrate dissolves in water, it absorbs heat from the surroundings, causing the solution to become cold. This process is an endothermic reaction, as it requires energy input to proceed.

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DOK Level 1: Recall