07. Chemical Reactions

• Describe and explain the effect of concentration, particle size, catalysts (including enzymes) and temperature on the rate of reactions

• Describe the application of the above factors to the danger of explosive combustion with fine powders (e.g. flour mills) and gases (e.g. methane in mines)

• Demonstrate knowledge and understanding of a practical method for investigating the rate of a reaction involving gas evolution

• Interpret data obtained from experiments concerned with rate of reaction

Note: Candidates should be encouraged to use the term rate rather than speed.

• Devise and evaluate a suitable method for investigating the effect of a given variable on the rate of a reaction

• Describe and explain the effects of temperature and concentration in terms of

collisions between reacting particles. (An increase in temperature causes an increase

in collision rate and more of the colliding molecules have sufficient energy (activation

energy) to react whereas an increase in concentration only causes an increase in

collision rate.)

• Describe and explain the role of light in photochemical reactions and the effect of

light on the rate of these reactions. (This should be linked to section 14.4.)

• Describe the use of silver salts in photography as a process of reduction of silver ions to silver; and photosynthesis as the reaction between carbon dioxide and water in the presence of chlorophyll and sunlight (energy) to produce glucose and oxygen

• Define oxidation and reduction in terms of oxygen loss/gain. (Oxidation state limited to its use to name ions, e.g. iron(II), iron(III), copper(II), manganate(VII).)

• Define redox in terms of electron transfer

• Identify redox reactions by changes in oxidation state and by the colour changes involved when using acidified potassium manganate(VII), and potassium iodide. (Recall of equations involving KMnO4 is not required.)

• Define oxidising agent as a substance which oxidises another substance during a

redox reaction. Define reducing agent as a substance which reduces another substance during a redox reaction.

• Identify oxidising agents and reducing agents from simple equations