Question

Discuss the following statement: If the temperature of the system increased, heat must have been added to it.

Answer 1

Consider the ideal gas law PV=nRT.
On one side you have Pressure and Volume. On the other side you've got the number of atoms, a constant (R), and Temperature.
If you keep the volume (V) the same and add more atoms (n) what happens to the Pressure (P)?

Answer 2

it increases?

Answer 3

Right, if you double the atoms then you double the pressure.\[2PV = 2nRT\]Keep the pressure the same then you double the volume.

Answer 4

I'm a little confused; what does that have to do with the heat?

Answer 5

There was another question, Heating an object causes its temperature to increase, which I answered by saying that the statement is not necessarily true. Heating an object does not always increase the temperature; for example, water when it is between two phases (liquid/solid or liquid/vapor) heating the water melts the ice into liquid or vaporizes that liquid into steam without increasing the temperature

Answer 6

I want to say that the statement that if temperature of the system increased heat must have been added to it is false because the temperature could increase without heat being added to a system

Answer 7

Taking the example of gas being compressed - that would increase the temperature without heat being added, right?

Answer 8

If the Temperature (T) goes up then:
If the Pressure stayed the same then the Volume went up (container expanded).
If the Volume stayed the same then the Pressure went up.
If the Pressure and Volume stayed the same then the number of atoms must have gone down.
Or any combination of these, filling a gas tank which has a fixed volume increases the number of atoms, increases the pressure, and increases the temperature. As the tank cools again the pressure goes up. It's always a balance.

Answer 9

so heat does not necessarily need to be added to change the temperature, you can vary other variables such as pressure, volume, etc?

Answer 10

Compress a gas (decrease the volume) increases the pressure, and temperature. Measure the volume and pressure, you can solve for the temperature.

Answer 11

okay I think I get it now ^_^

Answer 12

Thank you!

Answer 13

You can change everything but R (which is a constant) to change the temperature.

Answer 14

okay, thanks :)

Answer 15

I'll just throw this out there too, adding heat is still the easiest way to add heat.

Answer 16

yeah I figure it's easier to heat something than to compress it