The following slides should help you with your revision, but should not be your only form of revision. Remember to use your notes, a textbook, websites and Past Papers to help you. You can also ask a chemistry teacher for help too.
What is a chemical reaction? A chemical reaction is when one or more new substances are formed.
Give examples of a change in appearance? Bubbles of gas. A colour change. A solid forms. An energy change
Give examples of an energy change? A bright flame. A sound is produced. The container heats up or cools down.
What factors affect the speed of a reaction? Particle size. Concentration. Temperature. Presence of a catalyst.
An enzyme is a biological catalyst. What is an enzyme? An enzyme is a biological catalyst.
What name is given to a reaction in which heat is given out? An exothermic reaction.
What name is given to a reaction in which heat is taken in? An endothermic reaction.
Give examples of reactions. Iron rusting. Making toast. Epoxy resin glue setting. Lighting a match. Food going mouldy.
Give examples of physical change? Melting ice. Puddles evaporating. Nail varnish drying. Sugar dissolving.
Why does making the particle size smaller speed up the rate of a reaction? Smaller particle size increases the surface area. More surfaces for collisions to occur.
Give examples of a using smaller particle size to increase the rate of a chemical reaction? Using powdered chemicals rather than lumps of chemicals. Mince cooks quicker than lumps of beef.
Why does increasing the concentration speed up the rate of a reaction? Increases number of reacting particles. Increases number of collisions.
Give examples of a using higher concentration to increase the rate of a chemical reaction? Using bleach to take dyes out of clothes. Lab acid reacting faster with marble than Acid Rain with marble.
Why does increasing the temperature speed up the rate of a reaction? Increasing the temperature gives particles more energy. More collisions occur.
Give examples of a using higher temperature to increase the rate of a chemical reaction? Making toast, dries out bread quicker than leaving it out in the open. Car exhausts rust faster than the bodywork of a car.
Why does lowering the temperature decrease the rate of a chemical reaction? Decreasing the temperature, takes energy away from particles. Fewer particles collide.
Storing food in a fridge. Freezing food. Give examples of using a lower temperature to decrease the rate of a chemical reaction? Storing food in a fridge. Freezing food.
What is a catalyst? A catalyst speeds up the rate of a reaction, but is chemically unchanged itself at the end of the reaction.