5.1.1

Define the terms exothermic reaction, endothermic reaction and standard enthalpy change of reaction ().

1

Standard enthalpy change is the heat energy transferred under standard conditions—pressure 101.3 kPa, temperature 298 K. Only ∆H can be measured, not H for the initial or final state of a system.

5.1.2

State that combustion and neutralization are exothermic processes.

1

5.1.3

Apply the relationship between temperature change, enthalpy change and the classification of a reaction as endothermic or exothermic.

2

5.1.4

Deduce, from an enthalpy level diagram, the relative stabilities of reactants and products, and the sign of the enthalpy change for the reaction.

3

5.2.1

Calculate the heat energy change when the temperature of a pure substance is changed.

2

Students should be able to calculate the heat energy change for a substance given the mass, specific heat capacity and temperature change using q = mcΔT.

5.2.2

Design suitable experimental procedures for measuring the heat energy changes of reactions.

3

Students should consider reactions in aqueous solution and combustion reactions.

Use of the bomb calorimeter and calibration of calorimeters will not be assessed.

Aim 7: Data loggers and databases can be used here.

5.2.3

Calculate the enthalpy change for a reaction using experimental data on temperature changes, quantities of reactants and mass of water.

2

5.2.4

Evaluate the results of experiments to determine enthalpy changes.

3

Students should be aware of the assumptions made and errors due to heat loss.

TOK: What criteria do we use in judging whether discrepancies between experimental and theoretical values are due to experimental limitations or theoretical assumptions?

5.3.1

Determine the enthalpy change of a reaction that is the sum of two or three reactions with known enthalpy changes.

3

Students should be able to use simple enthalpy cycles and enthalpy level diagrams and to manipulate equations. Students will not be required to state Hess’s law.

TOK: As an example of the conservation of energy, this illustrates the unification of ideas from different areas of science.

5.4.1

Define the term average bond enthalpy.

1

5.4.2

Explain, in terms of average bond enthalpies, why some reactions are exothermic and others are endothermic.

3