Zusammenfassung der Ressource
Rates of Reaction
- The rate of reaction tells us how quickly a
chemical reactions happens
- Calculation: How much reactant is
used up ÷ time it takes to complete
the reaction
- eg. Amount of hydrogen gas formed
(cm3) ÷ Time for reactant to be used up
- Effect of Surface Area
- Measure of how much
surface is exposed
- As the surface area is increased,
the rate of reaction increases
- ex: A block a wood will burn slower than wood shavings
as there is less particles to react with on the surface.
- Explanation: As the surface area is increased, there
are more open particles that can be reacted with
- Collision Theory
- Before a chemical reaction
can start, particles must
crash together
- The more collisions between
particles in a given time, the
faster the reaction.
- Effect of Temperature
- When particles are heated,
they gain more thermal
energy and they move
around quicker.
- As they travel
faster, there are
more collisions
in a certain time.
- Therefore,
reactions get faster
as temperature is
raised.
- Also, some particles when
colliding just bounce off
each other because they
don't have enough energy.
- At higher temperatures,
particles are moving faster
and they collide with more
force, therefore more
collisions produce reactions.
- So raising the temperature:
1) Makes particles collide
more often in a certain time.
2) Makes it more likely that
collisions result in a
reactions.
- Catalysts
- A catalyst is a substance which
speed up a chemical reaction. At
the end of the reaction, the
catalyst is chemically unchanged.
- Before reactants can turn into
products, they need enough energy
to start the reaction.
- The energy needed to start a
reaction is called its ACTIVATION
ENERGY.
- A catalyst LOWERS the activation energy.
- Catalysts make it easier for particles
to react as less energy is needed to
start a reaction.