Chemistry AS AQA Unit 2 Particle Collisions

Made these notes for my year 12 summer exam to revise and read over. There are spelling mistakes in most of my files but due to the busy exam schedule I had no time to correct them (sorry).

Most files have more information than what is needed but I feel it helps you feel more confident walking into the exam if you have a greater knowledge background and may help when having to apply knowledge to questions. Good luck :)

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  • Created on: 02-09-13 13:36
Preview of Chemistry AS AQA Unit 2 Particle Collisions

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Particle collisions:
"Many collisions between molecules or other particles do not lead to reactions. They
either do not have enough energy or they are in the wrong orientation."
Increasing the concentration of a solution
If there are more particles in a given volume, collisions are more likely therefore the rate will be
Changes the rate of reaction without being chemically changed itself by providing an alternative
pathway for the reaction.
Increasing the temperature
This will increase the speed of molecules, which will increase their kinetic energy and hence
the number of successful collisions.
Increasing the pressure of a gas reaction
There are more molecules in a given volume, which means that collisions are more likely
hence increasing the rate of reaction.
Increasing the surface area of a solid reactant
This increases the number of particles available to collide with molecules (in a gas or a liquid),
otherwise known as increasing the number of sites.
Activation Energy, Ea
It is the minimum energy needed to start a reaction.
Exothermic Reactions
A reaction which gives out heat as the reactants change to products, thus the temperature rises.
The bonds are formed and energy is given out as forming bonds releases energy.
A reaction which heat is
taken in as the reactants
change to products, thus
the temperature drops.
The bonds are broken
and energy is taken in as
energy must be put in to
break bonds.

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No particles have zero energy
Most particles have intermediate
energies (around the peak of a
A few have very high energies
(the right side of the curve)
No upper limit
(Average energy is not the same
as most probable energy)
Most probable Average energy
The area under the
graph to the right of the
activation energy line
represents the number
of particles with enough
energy to react.
The temperature affects
the graph by the peak
becoming lower and
moves to the right.…read more

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HETEROGENEOUS CATALYSTS: Where the catalysts is in a different phase to the reactants- usually a
solid catalyst and liquid or gaseous reactants.
HOMOGENEOUS CATALYTS: Where catalyst and reactants are in the same phase.
Different phases are separated by a distinct boundary, for example, oil and water form two
separate liquid phases.
A catalytic convertor is a honeycomb shape made of ceramic material coated with platinum or
rhodium metals.…read more


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