Download Specific Heat and Calculating Heat Absorbed - Varga

Recall the definition of a calorie:
The amount of energy required to raise the temperature
of 1 gram of pure water by 1 degree Celsius.
Also recall that the calorie is equal to 4.184 J.
That quantity, 4.184 J/g°C, is known as the specific heat
of water. The symbol for specific heat is (c).
The specific heat of any substance is the amount of heat
required to raise one gram of the substance by one
degree Celsius.
To raise the temperature of water by 1 degree Celsius
requires 4.184 J of energy.
You will find that other substances require much less
energy to raise their temperatures by 1 degree Celsius.
It turns out that water has a much higher specific heat
capacity than concrete does.
The specific heat of concrete is 0.84 J/g°C, whereas the
specific heat of water 4.184 J/g°C.
If you have 1 kg of each substance at 0°C, which of them
will take more energy to raise to a temperature of
50°C?
It takes more energy to heat the water to 50
degrees Celsius than it takes to heat the
concrete block to 50 degrees Celsius!

It seems like if we know the specific heats of many
substances, we should be able to tell how much heat is
required to raise the substances to a certain
temperature.

And guess what? We can!
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It turns out that three important things matter when
calculating the heat lost or gained by a substance:
Mass
There is a direct relationship between
mass and the amount of heat required to
raise a substance to a specific
temperature. The symbol for mass is m.
In other words, the relationship between
mass and heat required is linear.
Temperature Change
The temperature that you want to raise a
substance to is equally important as the
mass of the substance that you have.
Temperature change is often given the
symbol Δt, and is equal to final
temperature – initial temperature.
Specific Heat
The specific heat of the substance is
important because it tells you exactly
how much heat is required to raise the
temperature of the substance.
The symbol for specific heat is (c).
These 3 important factors lead us to the heat equation:
q = mc Δt
Where:
q = heat (energy in J)
m = mass (in grams)
c = specific heat (in J/g°C)
Δt = temperature change (in °C)
1.
12 g of ethanol were heated from an initial
temperature 6.2 °C to a final temperature of
19.8 °C. How much heat was absorbed by
the ethanol?
2.
The temperature of a sample of iron with a
mass of 10.0 g changed from 50.4 °C to 25.0
°C with the release of 114 J. What is the
specific heat of iron?