You might have noticed that if you are trying to boil a lot of water
It takes longer than if you only wish to boil a small amount of water
This is all because of something called heat capacity
Keep watching to learn more
Before we get into details it is important to realize that there is a difference between heat and temperature
Temperature is a way of describing how hot or cold an object is and is measured in degrees Celsius
Whereas heat is a form of energy and is measured in joules?
The more heat transferred to an object the more its temperature will rise so heat and temperature are related, but they are not the same
So what is heat capacity?
The heat capacity of a substance is defined as the amount of heat required to raise the temperature of a material by one degree Celsius
However, what's more useful for us to think about is the specific heat capacity of the substance
This is as it says in the name a little bit more specific
It is the amount of heat required to raise one kilogram of a material by one degree Celsius
different materials have different known specific heat capacities
But we aren't always given a table like this so we need to know how to calculate specific heat capacities ourselves
We have this equation which can be written as symbols like this
The energy transferred is the heat energy absorbed or released
this equation can also be rearranged to
Work out, the temperature change subtract the old temperature from a new temperature
Let's have a look at a problem
Pause the video and attempt to calculate the specific heat capacity of lead
How did you get on?
The energy transferred is this
The mass is this and the temperature change is 10 degrees Celsius because it's this takeaway this
Using the rearranged equation substitute in the values and we get a hundred and twenty-eight joules per kilogram Celsius
Here is another practice problem pause the video and attempt to calculate the energy transferred to the LED
Did you get it right?
We could divide by 1000 to turn the answer into kilojoules
Notice that the answer is negative this time
It's because we called the LED the temperature change will always be negative if it is being cooled and positive if it is being heated
So there you have it to summarize
Specific heat capacity is the amount of energy needed to raise one kilogram of a substance by one degree Celsius
It's helpful because it allows us to work out how much energy we need to heat up or cool
down the substance to a desired temperature
To calculate it use the following equation
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