Understanding Reactions: Energy Changes

What is the definition of an endothermic reaction?

• An endothermic reaction is a process that does not involve temperature change.

• An endothermic reaction is a reaction that absorbs heat from its surroundings.

• An endothermic reaction occurs only in gases.

• An endothermic reaction releases heat into its surroundings.

Answer explanation

An endothermic reaction is defined as one that absorbs heat from its surroundings, leading to a decrease in temperature in the environment. This distinguishes it from exothermic reactions, which release heat.

What is the definition of an exothermic reaction?

• An exothermic reaction absorbs energy from the surroundings.

• An exothermic reaction occurs only in gases.

• An exothermic reaction is a reaction that releases energy, usually in the form of heat.

• An exothermic reaction is a process that does not involve heat transfer.

Answer explanation

An exothermic reaction is defined as one that releases energy, typically in the form of heat, to the surroundings. This distinguishes it from endothermic reactions, which absorb energy.

Can you provide an example of an endothermic reaction?

• Dissolution of salt in water

• Photosynthesis

• Respiration

• Combustion

Answer explanation

Photosynthesis is an endothermic reaction where plants absorb sunlight to convert carbon dioxide and water into glucose and oxygen, storing energy in the process. This distinguishes it from the other options, which are exothermic.

Can you provide an example of an exothermic reaction?

• Dissolving ammonium nitrate in water is an example of an exothermic reaction.

• Rusting of iron (4Fe + 3O2 -> 2Fe2O3) is an example of an exothermic reaction.

• Photosynthesis (6CO2 + 6H2O -> C6H12O6 + 6O2) is an example of an exothermic reaction.

• Combustion of methane (CH4 + 2O2 -> CO2 + 2H2O) is an example of an exothermic reaction.

Answer explanation

The combustion of methane is an exothermic reaction because it releases energy in the form of heat and light when methane reacts with oxygen, producing carbon dioxide and water.

What happens to energy during an endothermic reaction?

• Energy is converted into mass during the reaction.

• Energy is released into the surroundings.

• Energy is absorbed from the surroundings.

• Energy remains constant throughout the reaction.

Answer explanation

In an endothermic reaction, energy is absorbed from the surroundings, leading to a decrease in temperature of the environment. This distinguishes it from exothermic reactions, which release energy.

What happens to energy during an exothermic reaction?

• Energy remains constant throughout the reaction.

• Energy is absorbed from the surroundings.

• Energy is released into the surroundings.

• Energy is converted into mass.

Answer explanation

In an exothermic reaction, energy is released into the surroundings, often in the form of heat or light, indicating that the system loses energy while the surroundings gain it.

How does photosynthesis illustrate an endothermic reaction?

• Photosynthesis converts glucose into CO2 and H2O.

• Photosynthesis illustrates an endothermic reaction by absorbing sunlight energy to convert CO2 and H2O into glucose.

• Photosynthesis occurs only at night without sunlight.

• Photosynthesis releases energy by breaking down glucose.

Answer explanation

Photosynthesis is an endothermic reaction because it absorbs sunlight energy to convert carbon dioxide (CO2) and water (H2O) into glucose, demonstrating the process of energy absorption rather than release.

What is a common application of exothermic reactions in everyday life?

• Chemical fertilizers

• Hand warmers

• Ice packs

• Cooking food

Answer explanation

Hand warmers utilize exothermic reactions to generate heat, providing warmth when activated. This is a practical application of exothermic processes, unlike ice packs, which rely on endothermic reactions.

How do endothermic reactions affect temperature in their surroundings?

• Endothermic reactions have no effect on the temperature of their surroundings.

• Endothermic reactions lower the temperature of their surroundings.

• Endothermic reactions cause the surroundings to become warmer.

• Endothermic reactions increase the temperature of their surroundings.

Answer explanation

Endothermic reactions absorb heat from their surroundings, leading to a decrease in temperature. This is why the correct answer is that endothermic reactions lower the temperature of their surroundings.

Why are exothermic reactions important in energy production?

• Exothermic reactions produce waste that is harmful to the environment, limiting their use in energy production.

• Exothermic reactions are crucial in energy production because they release energy that can be harnessed for electricity generation and heating.

• Exothermic reactions are only useful in chemical manufacturing, not in energy generation.

• Exothermic reactions absorb energy, making them inefficient for energy production.

Answer explanation

Exothermic reactions are essential in energy production as they release energy, which can be utilized for generating electricity and providing heat, making them vital for various energy applications.