Transcript Slide 1

How many Joules of energy are required
to raise the temperature of 75 g of water
from 20.0oC to 70.0oC?
Heat
Heat =
= mass x ∆T x specific heat
75 g x 50.0 oC x 4.18 J/g oC
Heat = 15675 J ~ 16,000 J = 16 kJ
A 250.0 g metal bar requires 5.866 kJ to
change its temperature from 22oC to 100.0oC.
What is the specific heat of the metal?
Heat = mass x ∆T x specific heat
5.866 kJ = 250.0 g x 78 oC x Cp
5.866 kJ
=
Cp =
250.0 g x 78 oC
0.00030 kJ
g oC
= 0.30 J
g oC
The specific heat of zinc is 0.096 cal/goC.
Determine the energy required to raise the
temperature of 250.0 g of zinc from room
temperature (24oC) to 150.0oC.
Heat = mass x ∆T x specific heat
Heat = 250.0 g x 126 oC x 0.096 cal/goC
Heat = 3024 cal = 3.0 x 103 cal
= 3.0 kcal
A 20.0 g piece of metal at 203oC is dropped
into 100.0 g of water at 25.0oc. The water
temperature rises to 29.0oC. Calculate the
specific heat of the metal(J/goC). Assume
that all of the heat lost by the metal is
transferred to the water and no heat is lost
to the surroundings.
Heat = mass x ∆T x specific heat
Heat lost by metal = Heat gained by water
Heat = mass x ∆T x specific heat
Heat lost by metal = Heat gained by water
Heat gained by water:
Heat = 100.0 g x (29.0 – 25.0)oC x 4.18 J/goC
= 1672 J = 1700 J
Heat lost by metal:
1700 J = 20.0 g x (203 – 29.0)oC x Cp
oC
1700
J
=
.49
J/g
Cp =
20.0 g x 174oC