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This bundle is ideal for classroom or home learning and covers all of the OCR A level chemistry specification section 3.2. – physical chemistry. The topics covered are enthalpy changes, experimental determination of enthalpy changes, bond enthalpies, Hess’ Law measuring reaction rates, collision theory, factors affecting rates of reaction, dynamic equilibrium, le Chatelier’s principle, factors affecting position of equilibrium, industrial chemical processes and the equilibrium constant Kc.

Each topic includes a fully interactive PowerPoint including starter, group activities, questions and plenary along with a worksheet. Answers to all exercises are provided. Some of the resources include a PowerPoint quiz.

This bundle is part of a series covering the OCR AS Chemistry specification and relates to the following section:
Module 3 – Periodic table and energy
Part 2 – Physical chemistry
3.2.1 Enthalpy changes, 3.2.2 Reaction rates and 3.2.3 Chemical equilibrium

Content covered:
Enthalpy changes
• What is enthalpy
• Law of conservation of energy
• Enthalpy change
• Enthalpy profile diagrams
• System and surroundings
• Exothermic and endothermic reactions and examples
• Activation energy
• Standard enthalpy changes
• Standard conditions
• Definitions of enthalpy changes
• Simple calculations involving enthalpy changes

Experimental determination of enthalpy changes
• Energy exchange with the surroundings - heat loss in a chemical system = heat gain by surroundings
• Temperature scales
• Determining enthalpy changes using calorimetry
• Calculations involving q = mc∆T .
• Determining enthalpy changes in solution
• Determining enthalpy of combustion
• Errors associated with calorimetry experiments and how to minimise them
• Cooling curves and how to find the temperature rise
• Thermometric titration

Bond enthalpies
• Making covalent bonds (exothermic) and breaking covalent bonds (endothermic)
• Overall enthalpy change linked to relative enthalpies of breaking and making bonds – enthalpy profile diagram
• Average bond enthalpies and why they differ from actual bond enthalpies
• Factors affecting average bond enthalpies
• Calculations involving bond enthalpies
• Limitations of bond enthalpy calculations
• Plenary discussion about why there is a constant increase in the enthalpy change of combustion of alcohols for each CH2 group added

Hess’ Law
• Hess’ Law
• Indirect determination of enthalpy changes
• Enthalpy cycles
• Calculating enthalpy changes from enthalpy changes of combustion
• Calculating enthalpy changes from enthalpy changes of formation
• Summary of types of enthalpy calculation
• Calculating enthalpy changes from unfamiliar enthalpy cycles

Measuring rate of reaction
• Gradients
• Definition , calculation and units of rate of reaction
• Measuring rate of reaction experimentally using volume of gas, loss of mass or change in concentration
• Determining rate from a graph of concentration (or gas volume or mass loss) against time using tangents
• Smooth curve versus dot-to-dot

Collision theory and factors affecting rate of reaction
• Factors affecting rate of reaction
• The collision theory of reactions
• Activation energy and enthalpy profile diagrams
• Effect of concentration and pressure on rate and explanation in terms of collision theory
• Effect of temperature and catalysts on rate
• Catalysts – how they work and their advantages
• Using Boltzmann distribution curves and activation energy to explain the effect of temperature and catalysts on rate

Introduction to chemical equilibrium
• Static vs dynamic equilibrium
• Irreversible and reversible reactions
• Meaning of closed system
• Examples of dynamic equilibrium and how it is reached
• Definition of dynamic equilibrium
• How rates vary with time (graph of rate against time)
• How concentrations vary with time (graphs of concentration against time)
• Position of equilibrium – illustrated by concentration-time graphs
• Yield of reaction

Le Chatelier’s principle and equilibrium constant Kc
• Le Chatelier’s principle
• Effect of changing concentration, pressure or temperature on position of equilibrium, predicted and explained using le Chatelier’s principle
• Practical examples with colour changes
• Effect of adding a catalyst on rate of reaction and position of equilibrium
• Position of equilibrium and yield
• Choice of conditions in the chemical industry - factors considered including yield, rate , costs and safety
• How far, how fast?
• The Haber process as example of an industrial process
• The equilibrium constant Kc
• The equilibrium law
• Writing expressions for Kc and calculating values.

Links
Next lesson: – Introduction to organic chemistry (free resource)
Next bundle: Basic concepts of organic chemistry
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