Question | Answer |
What are exothermic reactions? | Reactions in which more energy is released making new bonds for the products than is needed to break the bonds of the reactants- so energy is released |
What are some examples of exothermic reactions? | Combustion of fossil fuels, explosions, bond making |
What are endothermic reactions? | Reactions in which more energy is needed to break the bonds of the reactants than is released by the making of new bonds for the products- so energy is absorbed |
What are some examples of endothermic reactions? | Photosynthesis, bond breaking |
What is the rate of a reaction? | The speed at which it takes place |
What are examples of very fast and slow reactions? | Very fast: explosions, combustion
Slow: rusting of iron |
What is the collision theory? | The theory that for a reaction to occur, there must be successful collisions between the reactants |
Why are not all collisions successful? | If the particles collide with low energy |
What are rates of reaction affected by? | * higher temperature increases the speed of particles so they are more likely to collide & with more energy * larger surface area of a solid allows more collisions at one time * higher concentration of solution increases amount of particles |
What is a catalyst? | A substance that speeds up the rate of a chemical reaction without being changed by the reaction |
What are the advantages of using a catalyst? | Chemical reactions can be done at lower temperatures and pressures so it is cheaper and safer |
What are catalytic converters and what are they made out of? | devices fitted to car exhausts that reduce the release of pollutants in exhaust gases- they combine CO and urburnt fuel with oxygen- they are made out of transition metals e.g platinum, palladium, rhodium in a honeycomb structure with a large surface area |
What conditions do catalytic converters work best in? | High temperatures- faster rates of reaction |