C7.1 - Chemical reactions Flashcards
Collision theory explains
why reactions occur and why they occur at different rates
For chemical reaction to occur
the reacting particles must collide with enough energy
The energy involved in collision must be
enough to break the chemical bonds
The minimum amount of energy required in collision is called
activation energy
Activation energy is
the minimum energy in which particles must collide in order to cause a chemical reaction
The rate of reaction is
the speed of a reaction
To increase the rate of reaction we need to increase
the “frequency” (word should be used in exam) collisions and/or the energy of the reactant particles
4 factors that affect rate of reaction are
Temperature
Concentration
Pressure (for gases)
Surface area
Increasing the concentration of dissolved reactants increases
the frequency of collisions as there are more particles in the same space which increases rate of reaction
increasing pressure increases
the frequency of collisions which increases rate of reaction
Increasing temperature increases frequency of collisions because
more heat in a particle transfers to more kinetic energy into the particle meaning it will move faster so more collisions will occur each second. They will also have more energy than the activation energy required.
Increasing surface area increases rate of reaction because
if there is more surface area than more particles can collide in which this is often done by breaking up solids into smaller lumps so that there is more exposure of a particle.
We can increase surface area by making substances into powders but some are dangerous like:
flour mills and coal mines which can be flammable and start a chain of explosive reactions
Catalysts are substances that
speed up a reaction without getting used up
catalysts increase/decrease rate of reaction
increase
