Energy Change Flashcards
what do chemicals store?
a certain amount of energy
what is an exothermic reaction?
an exothermic reaction is one which transfers energy to the surroundings usually by heating . It is evident by a temperature increase
what is an example of an exothermic reaction?
BURNING FUELS
NEUTRALISATION
OXIDISATION
what are everyday examples of exothermic reactions?
- hand warmers
- self heating cans
what is an endothermic reaction?
an endothermic reaction is one which takes in energy from the surroundings. This is evident by a temperature decrease
what is an example of an endothermic reaction?
sports injury cold packs
how can energy transfer be measured?
taking the temperature of the reagents, mixing them in a polystyrene cup and measuring the temperature of the solution at the end
why do you use a polystyrene cup?
to try reduce heat loss
how can you further reduce heat loss in the energy transfer experiment?
put the polystyrene cup into a beaker of cotton wool and use a lid
what is an example an energy transfer experiment?
HCL + NaOH
- put 25cm3 of 0.25 mol/dm3 of HCL and NaOH into separate beakers
- place beaker into water bathe 25 degrees
- take temperature every 30 seconds - record highest temperature
- repeat 1-4 with 0.5 mol/dm3 and 1 mol/dm3 of HCL
what is needed to break bonds ?
ENERGY
what happens during a chemical reactions (bonds) ?
old bonds are broken and new bonds are formed
what type of process is bonds breaking?
ENDOTHERMIC
what type of process is bonds forming?
EXOTHERMIC
what is electrolyte?
it is a liquid which contains ions that react with the electrode
