C5 Energy Changes Flashcards
what’s an exothermic reaction?
an exothermic reaction is on which transfers energy to the surroundings, usually by heating. this is shown by a rise in temperature
what is an endothermic reaction
an endothermic reaction is one which takes in energy from the surroundings. this is shown by a fall in temperature
examples of exothermic reactions everyday
hand warmers
self heating cans
examples of endothermic reactions everyday?
sports injury packs
how do you test the effect of acid concentration on the energy released in a neutralisation reaction between hydrochloric acid and sodium hydroxide?
1) put 25 cm cubed of 0.25 mol/dm cubed of hydrochloride acid and sodium hydroxide in separate beakers
2) place the beakers in a water bath set to 25 degrees until they are both at the same temp
3) add the hydrochloride acid followed by the sodium hydroxide to a polystyrene cup with a lid
4) take the temperature every 30 secomnds amd reacor the highest temperature
5) repeat steps 1-4 using 0.5 mol/dm cubes and then 1 mol/dm cubed of hydrocholic acid
what happens during a chemical reaction?
old bonds are broken and new bonds are formed,
energy must be supplied to break existing bonds - endothermic processes
energy must be released when new bonds are formed - exothermic process
bendo
break bonds - endothermic
mexo
make bonds - exothermic
what does an exothermic reaction profile look like
the reactants are at a higher energy than the products. the initial rise in the line represents the energy needed to break the old bonds and start the reaction. the different in height represents overall energy change represent the energy given out.
what is the activation energy?
the minimum amount of energy the reactants needed to collide with each other and react.the different in height represents overall energy change represent the energy taken in
what does an endothermic reation profle look lie?
the reactants are lower energy than the products
