3 Physical chemistry

Know that chemical reactions in which heat energy is given out are described as exothermic, and those in which heat energy is taken in are described as endothermic

Describe simple calorimetry experiments for reactions such as combustion, displacement, dissolving and neutralisation

Calculate the heat energy change from a measured temperature change using the expression Q = mcΔT

Calculate the molar enthalpy change (ΔH) from the heat energy change, Q

Draw and explain energy level diagrams to represent exothermic and endothermic reactions

Know that bond-breaking is an endothermic process and that bond-making is an exothermic process

Use bond energies to calculate the enthalpy change during a chemical reaction

Practical: investigate temperature changes accompanying some of the following types of change:

• salts dissolving in water
• neutralisation reactions
• displacement reactions
• combustion reactions.

Describe experiments to investigate the effects of changes in surface area of a solid, concentration of a solution, temperature and the use of a catalyst on the rate of a reaction

Describe the effects of changes in surface area of a solid, concentration of a solution, pressure of a gas, temperature and the use of a catalyst on the rate of a reaction

Explain the effects of changes in surface area of a solid, concentration of a solution, pressure of a gas and temperature on the rate of a reaction in terms of particle collision theory

Know that a catalyst is a substance that increases the rate of a reaction, but is chemically unchanged at the end of the reaction

Know that a catalyst works by providing an alternative pathway with lower activation energy

Draw and explain reaction profile diagrams showing ΔH and activation energy

Practical: investigate the effect of changing the surface area of marble chips and of changing the concentration of hydrochloric acid on the rate of reaction between marble chips and dilute hydrochloric acid

Practical: investigate the effect of different solids on the catalytic decomposition of hydrogen peroxide solution

Know that some reactions are reversible and this is indicated by the symbol ⇌ in equations

Describe reversible reactions such as the dehydration of hydrated copper(II) sulfate and the effect of heat on ammonium chloride

Know that a reversible reaction can reach dynamic equilibrium in a sealed container

Know that the characteristics of a reaction at dynamic equilibrium are:

• the forward and reverse reactions occur at the same rate
• the concentrations of reactants and products remain constant.

Understand why a catalyst does not affect the position of equilibrium in a reversible reaction

Know the effect of changing either temperature or pressure on the position of equilibrium in a reversible reaction:

• an increase (or decrease) in temperature shifts the position of equilibrium in the direction of the endothermic (or exothermic) reaction
• an increase (or decrease) in pressure shifts the position of equilibrium in the direction that produces fewer (or more) moles of gas References to Le Chatelier's principle are not required