Note:
IGCSE Chemistry Notes on Chemical Reactions
Syllabus Objectives:
7.1 Physical and chemical changes
Core
- Identify physical and chemical changes, and
understand the differences between them
7.2 Rate (speed) of reaction
Core
- 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.
Supplement
- 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
7.3 Reversible reactions
Core
- Understand that some chemical reactions can
be reversed by changing the reaction conditions.
(Limited to the effects of heat and water on
hydrated and anhydrous copper(II) sulfate and
cobalt(II) chloride.) (Concept of equilibrium is
not required.)
Supplement
- Predict the effect of changing the conditions
(concentration, temperature and pressure) on
other reversible reactions
- Demonstrate knowledge and understanding of
the concept of equilibrium