4.1- ENDOTHERMIC AND EXOTHERMIC REACTIONS Flashcards
What do most chemical reactions do when they proceed? (hint- energy)
give out or take in energy as they proceed
What can you do with the amount of energy involved when a chemical reaction takes place? (4)
measure energy values of fuels
calculate requirements for industrial processes
work out theoretical amount of energy to break bonds + amount of energy released when bonds made
helps predict whether or not reaction will take place
What forms can the energy involved in a chemical reaction be in? (3)
light, electrical, or most usually heat
What is thermochemistry the study of?
study of heat changes during chemical reactions
What happens to chemical bonds when a chemical reaction takes place?
chemical bonds break + new ones formed
What must be put in for bonds to break?
energy must be put in
What must be given out when bonds formed?
energy must be given out
As energy must be put in for bonds to break and energy given out for bonds to be broken, what do most chemical reactions involve?
involve energy change
What may the overall energy change in a chemical reaction result in?
energy being given out or taken in
What sort of reaction is it when energy has been given out?
reaction is exothermic
What sort of reaction is it when energy has been taken in?
reaction is endothermic
What do some reactions give out as they proceed?
heat
What are reactions that give out heat as they proceed called?
exothermic reactions
What is an example of an exothermic reaction?
neutralising an acid with an alkali
Where do some reactions take in heat from to keep the reaction going?
heat from surroundings
What is an example of an endothermic reaction? (hint- limestone)
breakdown of limestone (calcium carbonate) to lime (calcium oxide) + carbon dioxide
What is another example of an endothermic reaction? (hint- copper sulphate)
heating copper sulphate
What is the formula for blue copper sulphate crystals?
CuS04.5H20
How is the water molecules “with” the copper sulphate in blue copper sulphate crystals?
water molecules bonded to copper sulphate
What must be done to make white anhydrous copper sulphate from blue copper sulphate crystals?
bonds must be broken between water molecules and copper sulphate
What must be supplied to break the bonds between the water molecules and copper sulphate in blue copper sulphate crystals?
heat energy must be supplied
If a reaction is endothermic in one direction, what would it be like in the reverse direction?
exothermic
What is the amount of heat given out or taken in during a chemical reaction dependent on?
quantity of reactants
What is the energy usually measure in?
kJmol-1
What is there a large output of when fuels are burnt?
there’s a large heat output
What sort of reaction is it when fuels are burnt and there’s a large heat output?
very exothermic reactions
Example of endothermic reactions for cold packs?
NH4N03(s) + (aq) -> NH4N03(aq)
