BRAINCAKEEndothermic Reactions
In an endothermic reaction energy is taken in from the surroundings, so the temperature of the surroundings falls. The products have more enthalpy than the reactants and ΔH is positive.
On a reaction profile the products are drawn higher than the reactants. The enthalpy change ΔH is the vertical difference between the reactants and the products, shown by an arrow pointing upwards.
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Key terms in this lesson
- Enthalpy
- A measure of the heat energy stored in a chemical system.
- Enthalpy change
- The heat energy transferred between the system and its surroundings during a process carried out at constant pressure.
- Endothermic
- Describes a reaction in which energy is transferred from the surroundings to the system, so the enthalpy change is positive.
- Activation energy
- The minimum energy required for a reaction to take place.
- Transition state
- The highest-energy, short-lived arrangement of atoms during a reaction, in which bonds are part broken and part formed.
More in Kinetics
- Collision Theory
- Factors Affecting Rate of Reaction
- Activation Energy
- Exothermic Reactions
- Maxwell-Boltzmann Distribution
- Maxwell-Boltzmann Distribution and Activation Energy
- The Effect of Temperature on Reaction Rate
- Catalysts
All 14 lessons in Kinetics · All AQA AS-level Chemistry topics