Rate of reactions

heat of reaction (∆H)

net change of chemical potential energy of the system

exothermic reactions

reactions which transform chemical potential energy into thermal energy

endothermic reactions

reactions which transform thermal energy into chemical potential energy

bond breaking

energy and that bond formation releases energy.

stronger bond requires

more energy to break and releases more energy when formed

∆H > 0

endothermic reaction

∆H < 0

exothermic reaction

exothermic reactions release heat thus

increase the temperature of the surroundings

endothermic reactions absorb heat thus

decrease the temperature of the surroundings

activation energy

the minimum energy required to start a chemical reaction

Define the activated complex

a high energy, unstable transition state between the reactants and the products

Define reaction rate

the change in amount or concentration per unit time of either a reactant or product

average and instantaneous reaction rate

average reaction rate measures the change in reactant or product concentration over a period of time, while the instantaneous reaction rate measures the rate of change at a specific point in time. 

factors that affect the rate of chemical reactions

These include concentration of reactants, temperature, surface area, catalysts, and pressure (for gases).

Define a catalyst

A substance that increases the rate of a chemical reaction without being consumed in the process.

Explain that the collision theory

a reaction will only proceed when reactant particles collide effectively. An effective (or successful) collision is one instates that for a reaction to occur, reactant particles must collide with sufficient energy and the correct orientation.

Explain in terms of the collision theory that reaction rate is directly proportional to

the number of effective collisions per unit time

Suggest and explain suitable experimental techniques for measuring the rate of a given reaction

measuring of gas volumes, turbidity (e.g. precipitate formation), change of colour and the change of the mass of the reaction vessel over time to determine reaction rates.