International Baccalaureate IB Chemistry

Chemical reactions involve a transfer of energy between the system and the surroundings, while total energy is conserved.

Understand the difference between heat and temperature.

Reactions are described as endothermic or exothermic, depending on the direction of energy transfer between the system and the surroundings.

Understand the temperature change (decrease or increase) that accompanies endothermic and exothermic reactions.

The relative stability of reactants and products determines whether reactions are endothermic or exothermic.

Sketch and interpret energy profiles for endothermic and exothermic reactions.

The standard enthalpy change for a chemical reaction, $\Delta H^\circ$, 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. Apply the equations $Q = mc\Delta T$ and $\Delta H = -Q/n$ in the calculation of the enthalpy change of a reaction.

The units of $\Delta H^\circ$ are $\mathrm{kJ\,mol^{-1}}$.