Density

[wambam]

This is a very basic question but I'm somehow not grasping this concept.. the question in my EK physics 1001 book is:

A rigid container holds air (density 1.3 kg/m3) at 0 degree celcius. If the temp is increased to 273 degree celcius, what is the new density of the air?
-The answer is that the since the volume and mass remained the same, so the density remains the same.

I understand that logic can come from the p=m/v equation but I thought that if the temperature increases the density decreases because stuff expand when it's heated. Which is more correct?

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[chiddler]

The reason it does not change, given what you said, is because it is inside a container. It cannot expand! It wants to expand, which is why you'll see high pressure with increased temp, but it will not expand. Therefore, mass and volume remain the same.

 

[wambam]

That makes sense - thank you!!