ENERGY CHANGES Flashcards
what is an exothermic energy transfer
transfer to the surroundings
what is an endothermic energy transfer
transfer from the surroundings
what is a reaction profile
diagram showing how the energy changes in a reaction
what is bond energy
the energy required to break a bond or the energy released when making the bonds
what is activation energy
minimum amount of energy required before a collision will result in a reaction
in terms of bond making and breaking what is an exothermic reaction
less energy is required to break the bonds than is released when making bonds
in terms of bond making and breaking what is an endothermic reaction
more energy is required to break the bonds than is released when making bonds
how are chemical cells made
connect two different metals (electrodes) in a solution (electrolyte)
what is a battery
two or more chemical cells connected in series
how does the p.d of a cell depend on the metals that the electrodes are made of
the bigger the difference in reactivity, the greater the p.d
how can some cells be recharged
by applying an external current
why can some cells not be recharged
the reaction cannot be reversed
what is a fuel cell
cell that uses a fuel and oxygen to generate electricity
in the hydrogen fuel cell what is the overall reaction
2H2 + O2 —-> 2H2O
give an advantage of the hydrogen fuel cell
only product is water, do not need to be electrically recharged
