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 total energy of a chemical system.
- Enthalpy change
- The heat energy that is transferred between the system and its surroundings during a process carried out at constant pressure.
More in Enthalpy
- Enthalpy and Enthalpy Changes
- Activation Energy
- Standard Enthalpy Changes and Standard Conditions
- Enthalpy Change of Reaction
- Enthalpy Change of Formation
- Enthalpy Change of Combustion
- Enthalpy Change of Neutralisation
- Measuring the Enthalpy Change of Combustion
All 19 lessons in Enthalpy · All OCR AS-level Chemistry topics