Italics Topics are Triple Science ONLY
, Chapter 8 – Rates of Reaction
- The rate of a reaction can be found by monitoring the amount of reactants used up over time.
- Alternatively, you can find out the rate of reaction by measuring the amount of products made over time.
- The gradient of a line on a graph tells you the rate of the reaction, a steeper gradient means a faster reaction.
- To calculate the rate of a reaction at a specific time, draw the tangent to a curve then calculate its gradient.
- An example of a controlling the rates of reaction in everyday life is cooking cakes in an oven or adding more
- detergent to the washing machine.
- There are four main factors that affect the rate of chemical reactions:
• Temperature
• Surface area of solids
• Concentration of solutions or pressure of gases
• The presence of a catalyst
- Reactions can only take place when particles (atoms, ions or molecules) of reactants come together. They need
- to collide with enough energy to cause a reaction to take place. This is known as the collision theory.
- The minimum amount of energy that particles must have before they can react is called the activation energy.
- Increasing the frequency or increasing the energy of particles increases the rate of reaction.
, Chapter 8 – Factors affecting rates of reaction
- Surface area affects the rate of reaction. It can be investigated using marble chips and marble powder with HCl.
- The smaller the size of the pieces of solid material, the larger its SA:V ratio.
- In a large lump of solid, particles inside cannot react with the solution, so they have to wait for the particles on
- the surface to react first. This slows the reaction down.
- In a smaller lump of solid, like powder, each tiny piece of solid is surrounded by solution, so more particles are
- exposed to the solution meaning the reaction can take place quicker.
- Temperature affects the rate of reaction. It can be investigated
- using different temperatures of sodium thiosulfate with HCl.
- A higher temperature means that the particles collide more
- often and with more energy.
- When particles collide more frequently, it increases chances of
- them reacting thus increasing the rate of reaction.
- Concentration affects the rate of reaction. It can be investigated
- using HCl and Mg strips or sodium thiosulfate with HCl. Low Surface Area High Surface Area
- A higher concentration means that there are more particles in Low Concentration High Concentration
- a volume. As they are ‘more crowded’, collision is more likely. Low Pressure High Pressure
- This increases the frequency of collisions which increases Low Temperature High Temperature
- rate of a reaction. Low Rate High Rate
, Chapter 8 – Catalysts on Rates of Reaction
- Some reactions only work in extreme temperatures or extreme pressures.
- This in industry costs lots of money, however, reactions can be sped up & reduce energy costs using catalysts.
- A catalyst is a substance that changes the rate of a reaction, but it isn’t used in the reaction, so can be reused.
- Many of the catalysts in industry involve transition metals. Different ones are used for different reactions.
- Examples include iron, used to make ammonia, and platinum, used to make nitric acid.
- Catalysts are used normally in the form of powders, pellets, or fine gauzes. This gives them the biggest
- possible SA:V ratio, making them as effective as possible as the reactions they often catalyse involve gases
- reacting on their surfaces.
- Catalysts increase rates by providing an alternative reaction
- pathway to the products with a lower activation energy.
- This means, that with a catalyst a higher proportion of reactant
- particles have sufficient energy to react.
- It increases the frequency of EFFECTIVE collisions.
- Usually cheaper to use catalyst than to pay for extra energy. (+)
- Catalysts save money, energy, and so the environment. (+)
- Preserves non-renewable resources. (+)
- Stops more CO2 entering the atmosphere when burnt. (+)
, Chapter 8 – Rates of Reaction
- The rate of a reaction can be found by monitoring the amount of reactants used up over time.
- Alternatively, you can find out the rate of reaction by measuring the amount of products made over time.
- The gradient of a line on a graph tells you the rate of the reaction, a steeper gradient means a faster reaction.
- To calculate the rate of a reaction at a specific time, draw the tangent to a curve then calculate its gradient.
- An example of a controlling the rates of reaction in everyday life is cooking cakes in an oven or adding more
- detergent to the washing machine.
- There are four main factors that affect the rate of chemical reactions:
• Temperature
• Surface area of solids
• Concentration of solutions or pressure of gases
• The presence of a catalyst
- Reactions can only take place when particles (atoms, ions or molecules) of reactants come together. They need
- to collide with enough energy to cause a reaction to take place. This is known as the collision theory.
- The minimum amount of energy that particles must have before they can react is called the activation energy.
- Increasing the frequency or increasing the energy of particles increases the rate of reaction.
, Chapter 8 – Factors affecting rates of reaction
- Surface area affects the rate of reaction. It can be investigated using marble chips and marble powder with HCl.
- The smaller the size of the pieces of solid material, the larger its SA:V ratio.
- In a large lump of solid, particles inside cannot react with the solution, so they have to wait for the particles on
- the surface to react first. This slows the reaction down.
- In a smaller lump of solid, like powder, each tiny piece of solid is surrounded by solution, so more particles are
- exposed to the solution meaning the reaction can take place quicker.
- Temperature affects the rate of reaction. It can be investigated
- using different temperatures of sodium thiosulfate with HCl.
- A higher temperature means that the particles collide more
- often and with more energy.
- When particles collide more frequently, it increases chances of
- them reacting thus increasing the rate of reaction.
- Concentration affects the rate of reaction. It can be investigated
- using HCl and Mg strips or sodium thiosulfate with HCl. Low Surface Area High Surface Area
- A higher concentration means that there are more particles in Low Concentration High Concentration
- a volume. As they are ‘more crowded’, collision is more likely. Low Pressure High Pressure
- This increases the frequency of collisions which increases Low Temperature High Temperature
- rate of a reaction. Low Rate High Rate
, Chapter 8 – Catalysts on Rates of Reaction
- Some reactions only work in extreme temperatures or extreme pressures.
- This in industry costs lots of money, however, reactions can be sped up & reduce energy costs using catalysts.
- A catalyst is a substance that changes the rate of a reaction, but it isn’t used in the reaction, so can be reused.
- Many of the catalysts in industry involve transition metals. Different ones are used for different reactions.
- Examples include iron, used to make ammonia, and platinum, used to make nitric acid.
- Catalysts are used normally in the form of powders, pellets, or fine gauzes. This gives them the biggest
- possible SA:V ratio, making them as effective as possible as the reactions they often catalyse involve gases
- reacting on their surfaces.
- Catalysts increase rates by providing an alternative reaction
- pathway to the products with a lower activation energy.
- This means, that with a catalyst a higher proportion of reactant
- particles have sufficient energy to react.
- It increases the frequency of EFFECTIVE collisions.
- Usually cheaper to use catalyst than to pay for extra energy. (+)
- Catalysts save money, energy, and so the environment. (+)
- Preserves non-renewable resources. (+)
- Stops more CO2 entering the atmosphere when burnt. (+)
