c7//2 Flashcards
how do electrical cells work
using the differennce in reactivity of metals
what is a battery
the make up of two or more cells joined together
how is a higher voltage produced in a cell
the greater the difference in reactivity between the two metals.
what does the voltage in a cell also depend on
depends on the electrolyte
what happens in non rechargeable cells
once one of the reactants has run out, the cell will stop working
how can rechargeable cells be used again
cell is connected to a power supply which reverses the reactions that occur at each electrode which regenerates the original reactants
what is a fuel cell
is an efficient use of the energy from oxidising hydrogen
how fuel cells work
fuel cells are fed with hydrogen and oxygen to produce water. most of the energy released is transferred by electricity which can be used to do useful work.
where is hydrogen supplied to in a fuel cell
to the negative electrode and hydrogen diffuses through the electrode and reacts with hydroxide ions to form water
where is oxygen supplied to in a fuel cell
to the positive electrode where oxygen diffuses through the electrode and reacts with water to form hydoxide ions.
what is the overall change in the hydrogen fuel cell
the oxidation of hydrogen
what are advantages of hydrogen fuel cells
do not need to be electronically recharged
no pollutants produced (only water)
what are disadvantages of hydrogen fuel cells
hydrogen is highly flammable
hydrogen is difficult to store
what makes a metal more reactive in terms of ions
the metals tendency to form positive ions
give an advantage and disadvantage of reusable hand warmers against non reusable ones
advantage - less waste
disadvantage - has to be heated again which uses energy
