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Collision theory
- Reactions happen if particles collide, so if you increase the
number of collisions, the reaction happens more quickly. there are
4 factors that all lead to more collisions:
- Temperature, concentration, the presence of a catalyst
and the size of the particles
- Temperature, concentration, the presence of a catalyst
and the size of the particles
- Temperature
- Increasing the temperature means the particles are going faster and have more energy
- If the temperature is
increased: the reactant
particles move more quickly
they have more energy the
particles collide more often,
and more of the collisions
result in a reaction the rate of
reaction increases
- Higher temperatures also increase the energy of the collisions since the particals are
moving faster. reactions only happen if the particles collided with enough energy. at a
higher temperature there'll be more particles colliding with enough energy to make the
reaction happen.
- If the temperature is
increased: the reactant
particles move more quickly
they have more energy the
particles collide more often,
and more of the collisions
result in a reaction the rate of
reaction increases
- Increasing the temperature means the particles are going faster and have more energy
- Concentration
- Increasing the concentration ( or pressure ) means the particles are more
crowded together
- If the concentration of a dissolved
reactant is increased, or the pressure of
a reacting gas is increased: the reactant
particles become more crowded there is
a greater chance of the particles
colliding the rate of reaction increases
- If the concentration of a dissolved
reactant is increased, or the pressure of
a reacting gas is increased: the reactant
particles become more crowded there is
a greater chance of the particles
colliding the rate of reaction increases
- Increasing the concentration ( or pressure ) means the particles are more
crowded together
- Size of particles
- The rate of a chemical reaction can be raised
by increasing the surface area of a solid
reactant. This is done by cutting the
substance into small pieces, or grinding it into
a powder.
- Smaller solid particles ( or more surface area) means other particles can get to it more
easily
- Smaller solid particles ( or more surface area) means other particles can get to it more
easily
- If a solid reactant is broken into small pieces or ground into
a powder: its surface area increases more particles are
exposed to the other reactant there are more collisions the
rate of reaction increases
- For Example : calcium carbonate + hydrochloric acid = calcium
chloride dioxide + water
- Calcium carbonate is the chemical name for marble, you can change
the surface area by breaking large marble chips into small chips
- Calcium carbonate is the chemical name for marble, you can change
the surface area by breaking large marble chips into small chips
- For Example : calcium carbonate + hydrochloric acid = calcium
chloride dioxide + water
- Fine powders of combustion
materials dispersed in the air
burn very very fast because they
have such a big surface area, if
they spark they will explode
- Explosions are very fast reactions in which a lot
of gaseous product is released very quickly. For
example: burning hydrogen explosions from TNT
or dynamite
- Explosions are very fast reactions in which a lot
of gaseous product is released very quickly. For
example: burning hydrogen explosions from TNT
or dynamite
- The rate of a chemical reaction can be raised
by increasing the surface area of a solid
reactant. This is done by cutting the
substance into small pieces, or grinding it into
a powder.
- Catalysts
- A catalyst is a substance that can increase the rate
of a reaction, without being chemically changed or
used up in the reaction, and because it isn't used
up you only need a tiny bit of it to catalyst large
amounts or reaction
- Catalyst are very specific, they only work in certain reactions
- eg: iron, making ammonia from nitrogen and hydrogen
- eg: iron, making ammonia from nitrogen and hydrogen
- A catalyst works by giving the reaction particles a surface to stick to where they can
bump into each other, and reduces the energy needed by the particles before they
react.
- The number of collisions is NOT increased but there are just more
successful collisions
- The number of collisions is NOT increased but there are just more
successful collisions
- A catalyst is a substance that can increase the rate
of a reaction, without being chemically changed or
used up in the reaction, and because it isn't used
up you only need a tiny bit of it to catalyst large
amounts or reaction
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