Endothermic Reactions and Examples

A chemical reaction is a process in which one or more than one substance, known as reactants, are converted into one or more new substances, known as products, by breaking and forming chemical bonds. Chemical reactions are fundamental in chemistry and essential to understanding many natural and industrial processes.   

Chemical reactions can be classified as either exothermic or endothermic reactions based on the energy changes that occur during the reaction.  

An endothermic reaction requires energy to be absorbed from the surroundings. During an endothermic reaction, the reactants absorb energy, which decreases the temperature of the surroundings. This can be observed by measuring a decrease in the temperature of the reaction mixture, which usually feels cold to the touch.

In contrast, an exothermic reaction is a chemical reaction that releases heat energy into the surroundings. During an exothermic reaction, the reactants release energy, increasing the surroundings' temperature. This can be observed by measuring an increase in the temperature of the reaction mixture, which usually feels hot to the touch.   

Endothermic Reaction Examples  

Endothermic reactions are chemical reactions that absorb heat energy from their surroundings. Examples of endothermic reactions:  

• Melting of ice: When solid ice melts into liquid water, it absorbs heat energy from the surroundings. This is an endothermic process.  
• Photosynthesis: The process by which green plants and algae convert carbon dioxide and water into glucose and oxygen in sunlight is an endothermic reaction. It absorbs energy from the sun to produce glucose and oxygen.  
• Cooking an egg: When an egg is cooked, the heat energy from the stove is absorbed by the egg, which undergoes an endothermic reaction and changes from a liquid to a solid state.  
• Dissolving of ammonium nitrate in water: When dissolved in water, it absorbs heat from the surroundings, making the solution feel cold.  
• Reaction between baking soda and vinegar: When baking soda (sodium bicarbonate) is mixed with vinegar (acetic acid), it undergoes an endothermic reaction, which absorbs heat energy from the surroundings. This reaction is commonly used to make homemade volcanoes.  

Exothermic Reaction Examples  

Exothermic reactions are chemical reactions that release heat energy to their surroundings. Examples of exothermic reactions:  

• Combustion: The reaction of a fuel, such as gasoline or propane, with oxygen to produce carbon dioxide, water vapor, and heat energy is an exothermic reaction.  
• Neutralization: The reaction between an acid and a base to form salt and water is exothermic. This is because the reaction releases heat energy to the surroundings.  
• Rusting of iron: When iron reacts with oxygen in the presence of moisture, it forms iron oxide, releasing heat energy.  
• Formation of sodium chloride: The reaction between sodium and chlorine to form sodium chloride (table salt) is exothermic.  
• Polymerization: The process of linking monomer molecules to form a polymer is an exothermic reaction. This is because the reaction releases heat energy as the polymer is formed.  

Applications of Endothermic and Exothermic Reactions  

Endothermic and exothermic reactions have many important applications in various fields. Here are some examples:  

Applications of Endothermic Reactions:  

• Cooling systems: Endothermic reactions are used in cooling systems such as air conditioners and refrigerators. The evaporation of refrigerant compounds is an endothermic process that absorbs heat from the surroundings, cooling the area around the system.  
• Cold packs: Endothermic reactions are also used in cold packs, commonly used to treat minor injuries. The cold pack contains ammonium nitrate or other compounds that undergo an endothermic reaction when activated, absorbing heat from the surroundings and lowering the temperature.  
• Cooking: Endothermic reactions, such as baking or roasting food, are used in cooking. As the food absorbs heat from the oven or stove, it undergoes endothermic reactions and changes its internal chemistry to cook.  

Applications of Exothermic Reactions:  

• Heat generation: Exothermic reactions are used in various heating systems, such as combustion engines, furnaces, and boilers. The heat generated by the exothermic reaction provides warmth, generates electricity, and powers other machinery.  
• Explosives: Explosives are exothermic reactions that release substantial amounts of heat and energy in a short amount of time. They are used in various applications, such as mining, demolition, and military operations.  
• Chemical synthesis: Exothermic reactions are used in chemical synthesis, such as when combining two or more substances to form a new compound. The heat generated by the exothermic reaction can drive the reaction forward, forming the desired compound.