Endothermic Reactions (original) (raw)

Last Updated : 23 Jul, 2025

**Endothermic Reactions are a captivating and essential aspect of chemistry. In these reactions, a system absorbs heat from the surroundings, leading to a reduction in temperature. These reactions are present in our daily lives and are crucial to many industrial processes, biological functions, and even climate science.

In this article, we will explore the concept of endothermic reaction, endothermic **chemical reactions, characteristics, and real-life applications of endothermic reactions along with how endothermic reaction is different from exothermic reaction. The article will also highlight the endothermic process vs exothermic reaction with the energy level diagram of both. Also, check the sample questions and solutions on endothermic reactions at the end of the article.

Table of Content

• What is an Endothermic Reaction?
• Characteristics of Endothermic Reaction
• Real-Life Applications of Endothermic Reaction
• What is an Exothermic Reaction?
• Endothermic Reaction vs Exothermic Reaction

What is an Endothermic Reaction?

The Endothermic Reaction is a chemical reaction in which the reactants absorb the **heat energy from the surroundings to form the products. These chemical reactions cool down the surrounding environment by decreasing the temperature. For example, Ice cubes are a product of endothermic reaction. They absorb heat energy from their surroundings and melt to form liquid water.

**Reactants + Heat energy (usually represented on the reactant side) → Products

Definition of Endothermic Reaction

The Endothermic Reaction is a chemical reaction in which the reactants absorb the heat energy from the surroundings to form the products. It means that the temperature of the surroundings decreases as the reaction proceeds.

**Read more on the **Heat of Reaction Formula

Endothermic Reaction Equation Example

Here are some examples of endothermic chemical reactions:

**Melting of Ice: H 2 O (s) → H 2 O (l) + ΔH

**Evaporation of Water: H 2 O (l) → H 2 O (g) + ΔH

**Dissolution of Sodium Hydroxide in Water: NaOH (s) → NaOH (aq) + ΔH

Characteristics of Endothermic Reaction

Below-mentioned are the characteristics of endothermic reactions:

• One of the most important feature of endothermic reaction is the drop in temperature system
• Endothermic reactions are those reactions where is a positive change in **enthaply ΔH. Enthalpy helps in determining the total heat of the content system
• Some of the common examples of endothermic reaction is melting of ice, **evaporation of water, dissolution of sodium hydroxide in water, thermal decomposition of ammonium chloride

Real-Life Applications of Endothermic Reaction

Here are some real-life examples of endothermic reaction:

• Ice packs are a product of endothermic reaction and they help in cooling down the internal injuries
• Dehumidifiers are a product of endothermic reaction which helps in **condensation to remove moisture from the air
• Some fire extinguishers apply the chemical endothermic reaction to sublime and extinguish fire
• Endothermic reactions are also used in self-heating food containers to dissolving calcium oxide in water to heat up food
• Endothermic reactions are also used in cold packs that helps in dissolving ammonium nitrate in water to cool down things

What is an Exothermic Reaction?

The Exothermic Reaction is a chemical reaction in which the reactants release the heat energy in the surroundings through a chemical reaction or physical change. These chemical reactions heat the surrounding environment by increasing the temperature. For example, lighting a candle is a result of exothermic reaction. The flame heat the wax causing it to melt down and flow down the wick. The melted wax then produces heat, light and carbon dioxide.

Examples of Exothermic Chemical Reactions

Here are some examples of endothermic chemical reactions:

**Lightning a Candle: C n H 2n+2 + (n + 1) O 2 → n CO 2 + (n + 1) H 2 O + ΔH

**Burning a matchstick: P 4 + 5O 2 → 2P 2 O 5 + ΔH

**Rusting of iron: 4Fe + 3O 2 + 6H 2 O → 4Fe(OH) 3 + ΔH

**Also read: **Endothermic and Exothermic reactions

Endothermic Reaction vs Exothermic Reaction

The terms 'Endo' and 'Exo' are derived from greek dictionary meaning 'within' and 'out' respectively. Here are the key differences between the two:

**Learn more about **difference between endothermic and exothermic reactions

Is Photosynthesis an Exothermic or Endothermic Reaction?

Photosynthesis is an endothermic reaction. This is because the process of photosynthesis absorbs heat from it surroundings. The heat energy in the reaction helps in converting carbon dioxide and water into glucose and oxygen. Below-mentioned are some of the examples that how Photosynthesis is applied in the real-life:

• Photosynthesis helps in producing food which is later eaten by other animals
• Photsynthesis helps in producing biofuels such as ethanol and biodiesel
• Photosynthesis helps in producing oxygen for medical and industrial uses

How is Endothermic Process different from Exothermic Reaction?

Endothermic Process and Endothermic Reaction are both two related terms that are used in absorption of heat but they are not exactly same. In endothermic process, the process helps in absorbing heat from it surroundings from its physical or chemical change. Whereas, in endothermic reaction, it is a specific type of endothermic process that involves the transformation of reactions to products.

Energy Level Graph of Endothermic Reaction & Exothermic Reaction

Endothermic Reaction and Exothermic Reaction

**Check: Definition, Formula and Enthalpy Change

**Also, Check

• Enthalpy Change
• Entyropy Change

Sample Questions on Endothermic Reaction

**Question 1: What is an endothermic reaction and how it is different from endothermic process?

**Answer:

**Definition: The Endothermic Reaction is a chemical reaction in which the reactants absorb the heat energy from the surroundings to form the products.

Endothermic Process and Endothermic Reaction are both two related terms that are used in absorption of heat but they are not exactly same. In endothermic process, the process helps in absorbing heat from it surroundings from its physical change.

**Question 2: What are the real-life applications of endothermic reaction and exothermic reaction?
**Answer:

Endothermic Reaction Real-Life Applications:

• Ice packs are a product of endothermic reaction and they help in cooling down the internal injuries
• Dehumidifiers are a product of endothermic reaction which helps in condensation to remove moisture from the air
• Some fire extinguishers apply the chemical endothermic reaction to sublime and extinguish fire
  **Exothermic Reaction Real-Life Applications:
• Lighting a candle is a result of exothermic reaction. The flame heat the wax causing it to melt down and flow down the wick. The melted wax then produces heat, light and carbon dioxide
• Exothermic reactions are also helpful in generating electricity in power plants

**Question 3: Discuss the role of activation energy in endothermic reactions.
**Answer:

The role of activation energy in endothermic reaction is to provide a amount of energy to start a chemical reaction. Without activation energy in the chemical reaction, the reactants would not collide with enough energy to form the transition state and the chemical would not occur.

**Question 4: How is endothermic reaction is different from exothermic reaction?
**Answer:

**Endothermic Reaction: It is a chemical reaction in which the reactants absorb the heat energy from the surroundings to form the products. It provides a positive change in enthalpy.

**Exothermic Reaction: It is a chemical reaction in which the reactants release the heat energy in the surroundings through a chemical reaction or physical change. It provides a negative change in enthalpy.

**Question 5: What is enthalpy change in endothermic reactions. Give examples.
**Answer:

Enthalpy change (ΔH) in endothermic reaction is the change of total energy of a system during a chemical reaction. Here are some examples of endothermic reaction:

• **Melting of ice: ΔH = 6.01 kJ/mol
• **Photosynthesis: ΔH = 40.67 kJ/mol
• **Evaporation of water: 475 kJ/mol