It might come as a surprise but, specific heat capacity has plenty of real-world applications. Understanding this concept is an important step in understanding heat, temperature, and the world around you.
Read this guide for everything you need to know about specific heat. When conversions get tough, use our specific heat capacity calculator for instant and accurate results between 15 common units.
Before talking about specific heat capacity, it helps to understand what heat and temperature are.
Yes, heat makes things hot, and temperature is a measure of how hot something is. But let's get scientific.
Heat is the transfer of thermal energy between two objects and it's measured in units of Joules.
And temperature is the average kinetic energy of the constituent particles of a substance.
Every object is made up of particles, whether they're atoms or molecules. And in every object, those atoms and molecules are constantly vibrating and moving in random directions.
The higher the temperature of an object, the more the object's constituent particles move.
Temperature is measured in degrees Kelvin (or Celcius or Fahrenheit, but scientists use Kelvin).
To give you an idea of scale, if an object has a temperature of zero Kelvin, it's particles are completely motionless (this is impossible in practice).
Ice melts at 273 Kelvin and water evaporates at 373 Kelvin.
If you take two objects with different temperatures and put them next to each other, heat will flow from the object with higher temperature to the object with lower temperature.
This should be obvious to anyone who has touched something hot and felt a rush of heat.
And how much will the objects' temperatures change as a result of the transfer of heat?
To answer that, you need to understand heat capacity.
Heat capacity is a measure of how much the temperature of an object changes when you add heat to it.
For example, if you add heat to an object with high heat capacity, its temperature will barely change. But if the object had a low heat capacity, its temperature would skyrocket.
Think of it as a measure of how much heat the object can hold. The heat capacity of an object depends on the substance the object is made of, but it also depends on the mass of that object.
A giant tub of water will have a higher heat capacity than a small cup of water. That's because, in the giant tub, there's more water to disperse the incoming heat.
So heat capacity doesn't tell us much about the ability for the substance itself to absorb heat. For that, we need to understand specific heat.
Specific heat capacity is heat capacity divided by mass.
It answers the question: how many Joules of heat do I need to increase the temperature of one gram of something by one degree Kelvin?
This allows us to compare different substances without worrying about differences in mass.
For example, the tub of water and the cup of water have the same specific heat capacity.
The heat transfer equation helps us calculate quantities of heat and changes in temperature.
We've discussed the concepts of heat, temperature, and specific heat. Now, it's time to put them all together mathematically. This is the heat transfer equation:
Where:
How much heat is required to raise the temperature of a kilogram of water by ten degrees Kelvin?
We take the above equation, plug 1,000 grams in for m and 10 Kelvin in for ΔT. But what do we plug in for C? We have to find the specific heat of water.
Find a table of specific heat capacities online, and you'll see that water has a value of 4.18 Joules/gK. Plug that value in, solve the equation, and you get:
q = 41,800 Joules.
Now, consider a different problem:
How much will the temperature of a kilogram of silver increase if you add 41,800 Joules (the same amount of heat and mass as in the problem above)?
Let's first rearrange our equation to solve for ΔT. We get:
ΔT = q/(Cm)
Then, we look up the specific heat of silver (it's .24) and solve for ΔT. We get:
ΔT = 174 degrees Kelvin
Yikes, that's hot! It's much easier to raise the temperature of silver than water.
Water has an exceptionally high specific heat capacity. That's why it does such a good job of cooling you down.
If you tried to use a piece of cold silver to cool you down, it would quickly reach your skin temperature and stop transferring heat.
But water will absorb a lot more heat before it reaches your skin temperature (if it ever does).
The main reason for water's high specific heat capacity is its hydrogen bonds.
Hydrogen bonds are a force that exists between water molecules. It's the same force that makes the surface tension of water so devastating for anyone unlucky enough to fall off a bridge.
These bonds prevent water molecules from moving around too much and thus prevent a rise in temperature.
We won't get too deep into all the different factors that affect specific heat. Just remember that stronger internal bonds generally mean higher heat capacity.
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