collision theory

what is activation energy?

minimum energy that a particle needs in order to react: the energy difference between the reactants and the transitional state

What is a catalyst?

a substance that increases the rate of a reaction without being used in the process - provides alternate route with a lower activation energy

What is a heterogeneous catalyst?

a catalyst in a different phase from the reactants

what is a homogenous catalyst?

a catalyst in same phase as reactants

what affects the rate of reaction?

• temperature

• increasing concentration

• increasing pressure

• increasing surface area

• catalyst

how does increasing temperature affect the rate of reaction?

• increasing temperature increases rate of reaction

• reactant particles have greater kinetic energy at higher temperatures

• move a lot faster

• more of particles have energy that is greater than activation energy

• more successful collision

how does increase concentration affect rate of reaction?

• increasing concentration increases rate of reaction

• more reactant particles in same volume

• increase in number of collisions

• greater chance of successful collision

how does increasing pressure affect rate of reaction?

• increasing pressure increases rate of reaction

• more reactant particles in same volume

• increase in number of collisions

• greater chance of successful collision

How does increasing surface area affect rate of reaction?

• grinding solid into smaller pieces

• increases rate of reaction

• only particles on surface of a solid can collide with other reactant particles - increasing surface area increases no.particles able to collide

• increases number of collisions - increases chance of successful collisions

how to calculate rate of reaction?

draw triangle

change in y /change in x

how to measure rate of reactions?

• change in volume - with a syringe

• change in mass

• change in colour

draw an exothermic reaction pathway

draw an endothermic reaction pathway

describe this energy distribution curve.

• highest peak pf graph shows most probable energy at that temperature

• mean energy of particles always slightly higher then the most probable energy - the greatest number of particles having an energy greater than most probable energy

• no particles with an energy value at 0

• at higher energies the number of particles approaches 0 but never reaches 0

What are some properties of a catalyst?

• speed up reaction - not consumed by reactions - do not appear as reactants in equation

• alternative reaction pathway - activation energy lower than those of uncatylysed reactions

• alternate reaction pathway - activation energy lower by the same amount than the activation energies of reversible reaction

• catalysts speed up equilibrium without altering