energy changes Flashcards
endo vs exo
exo: energy TO the surroundings
endo: energy FROM the surroundings
do endo or exo reactions increase temperature
increase: exo
decrease: endo
what does an exothermic reaction look like on a graph
products is lower
what does an endothermic reaction look like on a graph
products are higher
what is activation energy and what does it look like on a reaction profile
minimum amount of energy needed for a reaction to happen
space between reactant and peak graph
on which reaction profile is energy release and which is energy absorbed
exo: release
endo: absorb
how do you work out the overall energy transferred in a reaction
bond breaking - bond making
4 examples of exothermic reactions
oxidation
combustion
neutralisation
hand warmers
2 examples of endothermic reactions
thermal decomposition
sports injury ice packs
how do rechargeable batteries work
external electric current applied, reverses reaction
what is chemical cell
two electrodes, connected by wire, in contact with an electrolyte. change flows
how does a chemical cell work
chemical difference between electrodes and electrolyte sets up potential difference between electrodes
wire enables this charge to flow, producing energy
what happens as the difference in reactivity increases in chemical cells
greater potential difference produced
what are fuel cells and how do they work
use a fuel and oxygen from air to generate electrical energy
fuel enters, becomes oxidised, sets up potential difference within cell
what happens in a hydrogen fuel cell
electricity generated from hydrogen and oxygen.
hydrogen is oxidised to produce water
