energetics Flashcards
what is enthalpy
the change in energy that normally occurs during a reaction
what is enthalpy change
the heat change in a reaction at constant pressure
what are the standard conditions
100 kPa pressure
298K (25°C)
what are endothermic reactions
reactions that absorb energy from the surroundings
what are exothermic reactions
reactions that release energy to the surroundings
in endothermic reactions, the products are … in energy than reactants, the delta H value is …
higher
positive
in exothermic reactions, the products are … in energy than reactants, the delta H value is …
lower
negative
to break a bond, energy needs to be …
absorbed
when bonds are formed, energy is …
released
when more energy is used to break bonds than make bonds, this is an … process and so delta H is …
endothermic
positive
when more energy is used to make bonds than break bonds, this is an … process and so delta H is …
exothermic
negative
enthalpy change =
total energy to break bonds - total energy released forming bonds
what is calorimetry used to work out
the enthalpy change of combustion
why are there wind shields and a lid in a calorimetry experiment
a lid is planed on top to prevent heat loss and wind shields placed by the flame to prevent a draught moving the flame
how to calculate energy transferred from calorimetry experiment
q = mcΔT
q - heat energy lost or gained (J)
m - mass of all liquids (g)
c - specific heat capacity of water (4.18)
T - temperature change (K)
