Exothermic and endothermic reactions and catalysts
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Explainer Video
Summary
Exothermic and endothermic reactions and catalysts
In a nutshell
Exothermic reactions release energy into the surrounding whereas endothermic reactions absorb energy from the surroundings. Catalysts are substances which increase the rate of reactions.
Energy
Energy cannot be created or destroyed, therefore the amount of energy in this universe will always be constant. Chemicals store energy.
In chemical reactions, sometimes chemicals absorb energy from the surrounding and sometimes they release energy into the surrounding; the energy transferred is usually in the form of heat.
Exothermic reactions
Definition
Exothermic reactions are reactions in which energy is transferred from the chemicals to the surrounding. Exothermic reactions increase the temperature of the surroundings.
Examples
Combustion and neutralisation reactions are examples of exothermic reactions. Self-heating cans of food contain chemicals that undergo exothermic reactions to release heat and warm the food.
 | Combustion of fossil fuels is an exothermic process as energy is released. |
Endothermic reactions
Definition
Endothermic reactions are reactions in which chemicals absorb energy from the surroundings. Endothermic reactions decrease the temperature of the surroundings.
There are fewer examples of endothermic reactions.
Examples
Decomposition reactions are examples of endothermic reactions and heat needs to be supplied for them to take place.
Injury packs involves endothermic reactions. Once the pack is snapped, endothermic reactions take place inside the pack which absorbs heat and make the pack feel cold. This can help with swelling.
Catalysts
Definition
Catalysts are substances which speed up the rate of reaction. Catalysts do not change or get used up reactions, therefore they are not included in equations.
Different reactions require different catalysts. Enzymes are catalysts which exist in nature.
Example
Lactase enzymes help break down lactose molecules in our body.
FAQs - Frequently Asked Questions
What is the purpose of a catalyst in a chemical reaction?
Catalysts are substances which speed up the rate of reaction. Catalysts do not change or get used up reactions.
What are exothermic reactions?
Exothermic reactions are reactions in which energy is transferred from the chemicals to the surrounding. Exothermic reactions increase the temperature of the surroundings.
What are endothermic reactions?
Endothermic reactions are reactions in which chemicals absorb energy from the surroundings. Endothermic reactions decrease the temperature of the surroundings.