energetics Flashcards
define an exothermic reaction.
a reaction during which energy is transferred from the system to the surroundings, meaning temperature rises
define an endothermic reaction
a reaction during which energy is transferred from the surroundings to the reactants.
give the word equation for energy change.
energy change = mass x specific heat capacity x temperature change
give the symbol equation for energy change
Q= m x c x (delta)T
give the word equation for enthalpy change
enthalpy change = energy/ number of moles (of limiting reagent)
give the symbol equation for enthalpy change
(delta)H = Q/n
define the enthalpy change
a measure of the change in the heat content of the reactants as the products are formed
in an exothermic reaction, is enthalpy change positive or negative and why?
in an exothermic reaction, enthalpy change is negative as energy is lost from the system
in an endothermic reaction is the enthalpy change positive or negative and why?
in an endothermic reaction the enthalpy change is positive as energy is taken into the system.
describe an experiment to investigate temperature change in displacement, dissolving and neutralisation reactions.
- put substance 1 into a polystyrene cup and record its temperature
- add substance 2 and stir with a thermometer. record the highest/lowest temperature
describe how to conduct an experiment to investigate temperature change in a combustion reaction
burn the chosen substance in a spirit burner. place the spirit burner under a beaker full of water and record the temperature change.
is bond breaking endothermic or exothermic?
endothermic
is bond making endothermic or exothermic?
exothermic
give the equation for enthalpy change in terms of bonds broken and bonds made
enthalpy change = bonds broken - bonds made
if energy used to break bonds > energy used to make bonds, then?
reaction is endothermic
