BRAINCAKEEndothermic and Exothermic Reactions
The law of conservation of energy states that energy cannot be created or destroyed. Energy can therefore be transferred between the system (reactants and products) and the surroundings (apparatus and the environment).
The enthalpy of a system cannot be directly measured, but the enthalpy changes can be measured experimentally. Enthalpy profile diagrams represent the relative enthalpies of reactants and products and the enthalpy change ΔH.
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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.
More in Energetics
- Enthalpy Change ΔH
- Physical States of Reactants and Products
- Enthalpy Level Diagrams
- Standard Enthalpies
- Measuring the Enthalpy Change of A Reaction
- Simple Colorimeter
- Flame Colorimeter
- Neutralisation Reactions
All 24 lessons in Energetics · All AQA AS-level Chemistry topics