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What affects the rate of a reaction? Size of Temperature reactant of reaction mixture Concentration of reactants catalyst /pressure

What affects the rate of a reaction? 1. The effect of particle size

1. The effect of particle size

What affects the rate of a reaction? 1. The effect of particle size •Reducing the size of particles •increases the surface area •increases the number of collisions per second. •Increase the number of effective collisions. •Increase the rate of reaction.

Increasing the Surface Area of a Solid. A solid in a solution can only react when particles collide with the surface. The bigger the area of the solid surface, the more particles can collide with it per second. A powder has the largest surface area and will have the fastest reaction rate.

THE EFFECT OF SURFACE AREA ON REACTION RATES a reaction between magnesium metal and a dilute acid like hydrochloric acid. Increasing the number of collisions per second increases the rate of reaction.

THE EFFECT OF SURFACE AREA ON REACTION RATES Magnesium metal

THE EFFECT OF SURFACE AREA ON REACTION RATES Magnesium metal

What affects the rate of a reaction? 2. Temperature Increasing temperature will increase energy in the particles leads to an increased probability of favourable collisions.

What affects the rate of a reaction? 1. The effect of temperature •Increase the temperature •increases the kinetic energy of particles •Increases the number of collisions per second. •Increase the number of effective collisions. •Increase the rate of reaction.

What affects the rate of a reaction? 3. Concentration and Pressure Increasing concentration or pressure increases the rate of a reaction, because the particles are closer together and have an increased probability of favourable collisions.



THE EFFECT OF CONCENTRATION ON REACTION RATES

THE EFFECT OF CONCENTRATION ON REACTION RATES

What affects the rate of a reaction? 1. The effect of concentration •Increase the concentration •increases the no of particles/unit volume •increases the number of collisions per second. •Increase the number of effective collisions. •Increase the rate of reaction.

THE EFFECT OF PRESSURE ON REACTION RATES

THE EFFECT OF PRESSURE ON REACTION RATES

What affects the rate of a reaction? 1. The effect of pressure in gas •Increase the pressure of gas •increases the no of particles/unit volume •increases the number of collisions per second. •Increase the number of effective collisions. •Increase the rate of reaction.

What affects the rate of a reaction? 4. Catalyst Often a catalyst is there to provide a favourable surface for a reaction to take place The black object represents the catalyst

Properties of Catalysts - A catalyst will change the rate of a reaction. - The catalyst itself does not take part in the reaction - It is not changed by the reaction - it is not used up during the reaction. - A catalyst is usually a transition metal, a transition metal oxide

Examples CATALYSTS ON REACTION RATES Reaction catalyst Decomposition of hydrogen Manganese peroxide (IV) oxide, MnO2 Manufacture of ammonia by the Haber Process Iron Contact Process to make sulphuric Vanadium acid (V) oxide, V2O5

What affects the rate of a reaction? 1. The effect of catalyst •Catalyst provides alternative route •That has a lower activation energy •So more particles have energy equal or greater than activation energy. •Number of effective collisions increase. •Increase the rate of reaction.

What affects the rate of a reaction? 4. Catalyst How does a catalyst work? 1) A catalyst provides a surface on which the reaction can take place. This increases the number of collisions between the particles of the substances that are reacting.

How does a catalyst work?

How does a catalyst work?

What affects the rate of a reaction? 4. Catalyst How does a catalyst work? 2) A catalyst lowers the activation energy This means that the particles can react with less energy than they needed before the catalyst was added. (Think about it: if the government lowered the legal age to buy cigarettes, then more people could legally buy cigarettes. Similarly, if we lower the amount of energy needed for particles to react, then more particles can react).

Activation energy A catalyst provides an alternative route for the reaction. That alternative route has a lower activation energy.

Activation energy Activation energy with no catalyst Activation energy with catalyst

Factors What Collision affecting? is ? theory? Rate of reaction Activation Energy level energy? diagram? Effective collision?

Energy level diagram In an exothermic reaction, reactants have a higher energy level than the products.

Energy level diagram In endothermic reactions the reactants have a lower energy level than the products.