SCH 4U1
CALCULATING THE HEAT
Suppose a propane torch was used to heat up a sample of
water. How is the heat that is transferred calculated?
There are three factors that affect the amount of heat.
1) The mass of the object – grams (g)
2) The temperature loss/gain – degrees Celsius (oC)
3) The specific heat capacity – the amount of heat required to
raise the temperature of 1.0 g of the substance 1.0oC – J/g.oC
So, amount of heat = mass x specific heat capacity x temperature
q = m x c x t
Problem 1
A 100.0 g sample of water (system) was heated by a propane
torch. The temperature rose from 16oC to 27oC, calculate the
heat gain in kJ.
Solution
m= ____________
t = ______________
c = 4.18 J/g oC
q = ______________
q = ______________________
q = __________________
Did the system go through an exothermic or endothermic
process?
__________________
The heat ___________ by the propane is equal and opposite to
the heat _____________ by the water.
Problem 2
A 25.0 g sample of ice (system) was heated on a stirring hot plate
until all the ice melted and the temperature of the water remains
at 0oC. Calculate the heat (in kJ) gained by the water/ice system.
Solution:
q=
q=
q=
q=
m x ∆Hfus
___________________
_________________
______________
Exo/endo = ______________________
Problem 3
A clear, colourless liquid with an initial mass of 154.4 g has some
of its vapour condense so the liquid has a final mass is 177.1 g. It
was calculated that 25.0 kJ of heat were removed during
condensation. Calculate the ∆Hvap. Is the substance water?
Solution:
q = m x ∆Hvap
∆Hvap = ______________
∆Hvap = ____________________
∆Hvap = ______________
This substance is ___________.
Exo/endo = ____________________