Calculating Heat Capacity
Heat capacity is the amount of energy required to increase
the temperature of an object by 1˚C. The amount of energy
depends on how big the object is (my Dodge Grand Caravan
takes longer to warm up in the morning than my Toyota Prius)
and what the object is made of (water in the tea kettle takes
longer to heat up than the metal of an empty tea kettle).
We can compare heat capacities of different materials by
using a number called the specific heat capacity, which is
really heat capacity per gram. Here is the formula.
Mass (g)
o
Change in Temp ( C)
Q = m × c × ΔT
Heat (J)
 J 

Specific Heat 
 g oC 


1) How much heat does it take to warm 50 g of water by
20˚C?
Substance
Specific
heat
J/g °C
Aluminum
0.900
Bismuth
0.123
Copper
0.386
Brass
0.380
Gold
0.126
Lead
0.128
Silver
0.233
Tungsten
0.134
Zinc
0.387
Iron
0.450
Mercury
0.140
Alcohol (ethyl)
2.400
Water
4.186
Ice (-10˚C)
2.050
Granite
0.790
Glass
0.840
2) How much heat does it take warm a 50 g coffee cup (glass) by
20˚C?
Good Stuff
Q = m × c × ΔT
m = Q ÷ (c × ΔT)
c = Q ÷ (m × ΔT)
ΔT = Q ÷ (m × c)
Power P = Q ÷ t
3) If the temperature of 100 g of Styrofoam went up 5˚C when you added 3,000 J of heat,
what is its specific heat?
4) The sun shines on a 1000 g rock (granite) and adds 1500 J of heat to the rock. How much
does its temperature rise?
5) Making Tea
A. A kettle (400 g of iron) is used to boil 1 liter of water (1000 g). If the kettle and
the water both start at 20˚C, how much heat does the stove have to produce for
the water to come to a boil (assuming all of the heat goes to warming the kettle and
the water)?
B. If you wanted to make your tea in 1 minute (60 s), how much power does the burner
need to generate?