an exothermic reaction is one that causes a rise in temperature to its surroundings. it releases energy
an endothermic reaction is one that causes a decrease in temperature in the surroundings. takes in energy
reacting particles must collide with sufficient energy in order for bonds to be broken
in a chemical reaction:
atoms are rearranged
old bonds broken
new bonds formed
activation energy is the minimum amount of energy that particles must have for a reaction to take place
catalysts increases the rate of reaction by reducing the activation energy and providing an alternate pathway
bond breaking = endothermic
bond making = exothermic
cells release energy by the chemicals inside reacting and releasing electricity
simple cells are made by placing 2 different metals into a beaker containing an electrolyte
a battery is 2 or more cells connected together
in a hydration fuel cell, hydrogen and oxygen are supplied to the cell. the fuel is oxidised to produce a potential difference, the hydrogen is oxidised to produce water
fuel cells are becoming more popular as traditional methods involve many stages, are less efficient and more polluting