4.1: How fast?
- Created by: Jordan64
- Created on: 23-04-16 12:19
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- C2.4: Rates and energy
- 4.1: How fast?
- 4.2: Collision theory and surface area
- 4.3: The effect of temperature
- Reactions happen more quickly as the temperature increases
- This means they collide more often, which increases the rate of reaction
- As well as colliding more frequently, they collide with more energy, which also increases the rate of reaction
- Reactions happen more quickly as the temperature increases
- This means they collide more often, which increases the rate of reaction
- As well as colliding more frequently, they collide with more energy, which also increases the rate of reaction
- As well as colliding more frequently, they collide with more energy, which also increases the rate of reaction
- Increasing the temperature increases the rate of reaction because particles collide more frequently and more energetically
- A small change in temperature has a large effect on reaction rates: a temperature rise of 10 degrees will roughly double reactions so they go twice as fast.
- Increasing the temperature increases the rate of reaction because particles collide more frequently and more energetically
- This means they collide more often, which increases the rate of reaction
- Reactions happen more quickly as the temperature increases
- As well as colliding more frequently, they collide with more energy, which also increases the rate of reaction
- A small change in temperature has a large effect on reaction rates: a temperature rise of 10 degrees will roughly double reactions so they go twice as fast.
- This means they collide more often, which increases the rate of reaction
- Reactions happen more quickly as the temperature increases
- 4.6: Catalysts in action
- Catalysts are used in industry to increase the rate of reactions and reduce energy costs.
- If fossil fuels are burned to provide energy for industrial reactions, using catalysts will help to conserve resources and reduce pollution.
- Some catalysts are expensive, but they can be economical because they do not need replacing very often
- This helps to reduce costs and reduce impacts on the environment.
- Many of the catalysts used in industry are traditional catalysts. They are often transition metals or their compounds
- Some of these metals and their compounds are toxic and may cause harm if they get into the environment
- They are used in many industrial processes because they can reudce the energy and the time needed for reactions.
- Modern catalysts are being developed in industry which result in less waste and are safer for the environment
- Finding new and better catalysts is a major area of research for the chemical industry.
- Nanoparticles offer exciting possibilities for developing new, highly efficient catalysts.
- If this can replace more traditional catalysts, they will reduce energy costs even further.
- Enzymes are biological catalysts that work at ordinary temperatures.
- If this can replace more traditional catalysts, they will reduce energy costs even further.
- Catalysts are used in industry to increase the rate of reactions and reduce energy costs.
- 4.5: The effect of catalysts
- A catalyst speeds up the rate of reaction
- They speed up the reactions and therefore lower the axctivation energy of the reaction so that more of the collisions result in a reaction
- A catalyst speeds up the rate of reaction
- 4.7: Exothermic and endothermic reactions
- Energy may be transferred to or from the reacting substances in a reaction
- When chemical reactions take place energy is transferred as bonds are broken and made
- A reaction in which energy is transferred from the reacting substances to their surroundings is called an exothermic reaction.
- The energy transferred often heats up the surroundings and so the temperature increases
- Exothermic reactions include:
- Combustion, such as burning fuels
- Neutralization reactions involving acids and bases
- Exothermic reactions include:
- The energy transferred often heats up the surroundings and so the temperature increases
- A reaction in which energy is transferred to the reacting substances from their surroundings is called an endothermic reaction
- Some cause a decrease in temperature and others require a supply of energy.
- When some solid compounds are mixed with water, the temperature decreases because endothermic changes happen as they dissolve
- Thermal decomposition reactions need to be heated continuously to keep the reaction going
- Some cause a decrease in temperature and others require a supply of energy.
- When some solid compounds are mixed with water, the temperature decreases because endothermic changes happen as they dissolve
- Thermal decomposition reactions need to be heated continuously to keep the reaction going
- Thermal decomposition reactions need to be heated continuously to keep the reaction going
- When some solid compounds are mixed with water, the temperature decreases because endothermic changes happen as they dissolve
- Some cause a decrease in temperature and others require a supply of energy.
- Thermal decomposition reactions need to be heated continuously to keep the reaction going
- When some solid compounds are mixed with water, the temperature decreases because endothermic changes happen as they dissolve
- Some cause a decrease in temperature and others require a supply of energy.
- Energy may be transferred to or from the reacting substances in a reaction
- 4.9: Using energy transfers from reactions
- Endothermic reactions can be used to cool things
- Endothermic changes can be used in instant cold packs for sports injuries
- Some chemical cold packs contain ammonium nitrate and water that are kept separated.
- When mixed together, the ammonium nitrate dissolves and takes in energy from the surroundings - this can be used on sports injuries, or to cool drinks.
- The reaction is reversible, but not in the pack, so this type of pack can only be used once.
- When mixed together, the ammonium nitrate dissolves and takes in energy from the surroundings - this can be used on sports injuries, or to cool drinks.
- Some chemical cold packs contain ammonium nitrate and water that are kept separated.
- Endothermic changes can be used in instant cold packs for sports injuries
- Exothermic changes can be used to heat things
- An example is hand-warmers and self-heating cans
- Some hand-warmers use a reversible reaction such as the crystalisation of a salt - once used, the pack can be heated in boiling water to re-dissolve the salt - this can be re-used many times
- Some hand warmers can't be used again because they use reactions such as the oxidation of iron or the reaction of calcium oxide with water - both non-reversible
- An example is hand-warmers and self-heating cans
- Endothermic reactions can be used to cool things
- An average rate can also be found by measuring the time it takes for a certain amount of solid in the solution.
- If a gas is given off in the reaction, it's average rate can be found by measuring the time taken to collect a certain amount of gas
- The gradient or slope of the line on a graph of amount of reactant or product against time tells ups the rate of reaction at that time.
- We can collect the data for the graph by measuring the mass of gas released or the volume of gas produced at intervals of time
- Other possible ways include measuring changes in colour, concentration or pH of a reaction mixture, over time.
- We can find the rate of a chemical reaction by measuring the amount of reactants used up over time or by measuring the amount of products made over time.
- An average rate can also be found by measuring the time it takes for a certain amount of solid in the solution.
- If a gas is given off in the reaction, it's average rate can be found by measuring the time taken to collect a certain amount of gas
- An average rate can also be found by measuring the time it takes for a certain amount of solid in the solution.
- Steeper gradient = faster reaction
- We can collect the data for the graph by measuring the mass of gas released or the volume of gas produced at intervals of time
- Factors that increase the chance of collisions, or the energy of the particles will increase the rate of reaction.
- Factors that will increase the rate of reaction include:
- Temperature
- Concentration of solutions
- Pressure of gases
- Surface area of solids
- Using a catalyst
- The minimum amount of energy that particles must have in order to react is called the activation energy
- Collision theory states that reactions can ONLY happen if particles collide
- 4.2: Collision theory and surface area
- Collision theory states that reactions can ONLY happen if particles collide
- Factors that will increase the rate of reaction include:
- The rate of a chemical reaction also increases if the surface area of any solid reactants is increased
- This increases the frequency of collisions between reacting particles
- Factors that increase the chance of collisions, or the energy of the particles will increase the rate of reaction.
- Factors that will increase the rate of reaction include:
- Temperature
- Concentration of solutions
- Pressure of gases
- Surface area of solids
- Using a catalyst
- The minimum amount of energy that particles must have in order to react is called the activation energy
- Collision theory states that reactions can ONLY happen if particles collide
- Collision theory states that reactions can ONLY happen if particles collide
- Factors that will increase the rate of reaction include:
- Increasing the pressure of a gas puts more molecules into the same volume, ad so they collide more frequently.
- This therefore increases the rate of reactions that have gases as reactants
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