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Reactivity 1.1.4—The standard enthalpy change for a chemical reaction, ΔH⦵, refers to the heat transferred at constant pressure under standard conditions and states. It can be determined from the change in temperature of a pure substance.


Here are experiments our science specialists have selected to support this IB* topic.

Determining the Enthalpy of a Chemical Reaction

Experiment #13 from Advanced Chemistry with Vernier

In this experiment, you will

  • Use Hess’s law to determine the enthalpy change of the reaction between aqueous ammonia and aqueous hydrochloric acid.
  • Compare your calculated enthalpy change with the experimental results.

Burning Accelerants

Experiment #6 from Forensic Chemistry Experiments

  • Compare the heat of combustion for two accelerants: the crime scene evidence and samples from arson suspects.
  • Calculate the heat of combustion in kJ/g.
  • Use your data and calculations to identify which suspect had the same accelerant as that used at the crime scene.

Educational Standard
International Baccalaureate (IB) 2025
Organizing concepts
Reactivity 1. What drives chemical reactions?
Reactivity 1.1—Measuring enthalpy changes
Standard level and higher level

* The IB Diploma Program is an official program of the International Baccalaureate Organization (IBO) which authorizes schools to offer it. The material available here has been developed independently of the IBO and is not endorsed by it.