Energy Changes Flashcards
whats an exothermic reaction?
transfers energy to the surroundings so temperature of surrounding increases
examples of exothermic reactions?
combustion, many oxidation reactions and neutralisation
what are everyday uses of exothermic reactions?
self heating cans and hand warmers
what are endothermic reactions?
takes energy in from surroundings so temperature of surroundings decreases.
examples of endothermic reactions?
thermal decomposition and reaction of citric acid and sodium hydrogencarbonate, sports injury packs
what is the activation energy?
minimum amount of energy that particles must have to react.
what must happen during a chemical reaction?
energy supplied to break bonds in reactants
energy released when bonds in the products are formed
what impacts the voltage produced by a cell?
the type of electrode and electrolyte
how can a simple cell be made?
connecting 2 different metals in contact with an electrolyte.
what do batteries that consist of 2 or more cells connected together in series provide?
a greater voltage
what happens in non-rechargeable cells and batteries?
chemical reactions stop when one of the reactants has been used up.
what happens in rechargeable cells and batteries?
chemical reactions are reversed when an external electrical current is supplied.
what are fuel cells supplied by?
an external source of fuel e.g hydrogen and oxygen or air.
fuel is oxidised electrochemically within a cell to produce a pd
