Question

What is absorbed by an endothermic reaction?

Short answer

An endothermic reaction absorbs heat (thermal energy).

Step-by-step solution

Define Endothermic Reaction

An endothermic reaction is a type of chemical reaction that absorbs energy from its surroundings in the form of heat. It results in a decrease in temperature of the surrounding environment as the reaction proceeds.

Identify the Absorbed Quantity

Since an endothermic reaction absorbs heat from its surroundings, the quantity absorbed in such reactions is thermal energy (heat). This absorption is necessary for the reaction to proceed as it overcomes the energy barrier.

Key concepts

Chemical Reaction

A chemical reaction involves the transformation of substances through the breaking of bonds in the reactants and the formation of new bonds to create products.
These reactions occur when two or more molecules interact, resulting in changes in their molecular structure.
In chemistry, reactions are divided into different categories based on their energy changes. A reaction can either release or absorb energy, categorized as exothermic or endothermic, respectively.

• Reactants and Products: In a chemical reaction, the starting substances are known as reactants and the substances formed are called products.
• Bond Breaking and Forming: The process involves breaking existing chemical bonds and forming new ones.
• Conservation of Mass: During chemical reactions, the total mass of the reactants equals the total mass of the products, demonstrating conservation of mass.

Endothermic reactions are a special subtype because they absorb energy, crucial for their progress.
This absorption supports the transformation by overcoming obstacles that might otherwise prevent the reaction from proceeding.

Thermal Energy

Thermal energy is a type of kinetic energy related to the movement of atoms and molecules in a substance.
When we talk about thermal energy in the context of chemical reactions, it is closely related to heat or the transfer of energy from one body to another due to temperature differences.

• Heat Transfer: In endothermic reactions, thermal energy is transferred from the surroundings into the reaction, causing the surrounding environment to cool.
• Temperature and Energy: The amount of thermal energy can affect how fast or slow a chemical reaction occurs. Increased temperatures typically increase reaction rates.
• Energy Absorption: Endothermic reactions require the absorption of thermal energy to progress as the energy is needed to break existing bonds in the reactants.

Understanding thermal energy's role in reactions is crucial, especially how it underlies the function of the reactions and their surroundings.

Energy Barrier

The energy barrier in chemical reactions refers to the minimum energy required to start a reaction.
This energy is necessary to break the bonds in the reactants and allow the formation of new bonds in the products. In endothermic reactions, overcoming this energy barrier is crucial for the reaction to proceed.

• Activation Energy: Often referred to as activation energy, it represents the obstacle that must be overcome for a reaction to commence.
• Role in Endothermic Reactions: In an endothermic reaction, thermal energy absorbed from the surroundings helps provide the energy needed to overcome this energy barrier.
• Influence on Reaction Rate: The height of the energy barrier affects how quickly a reaction can occur. A higher energy barrier means a slower reaction rate.

In endothermic reactions, continuously absorbing heat helps ensure that the reaction can surpass the energy threshold and proceed efficiently.