How is dense matter related to temperature?

Question

Piper Hoffman · Accepted Answer

The less energy there is (this could be heat energy - linking to temperature), the denser the object will be.

Particles that are more energetic will move faster and faster, which will cause them to become less dense and more dispersed. A water molecule that makes up solid, dense ice will have less energy than a water molecule that makes up gaseous, less dense steam, and as a result, an object with less energy is likely to be denser than one with more. Imagine a room full of toddlers; if they aren't feeling very energetic, they will all sit together and sleep in a small space, crammed together; if they are feeling very energetic, however, they will spread out and move around more. Let me know if there is anything else I can do. I hope this helps.

Piper Hoffman · Answer

In a perfect gas under constant pressure, the density is inverse proportional to the temperature.

This question is complicated because different particles behave depending on whether they are in a gas, solid, superfluid, or any other state of matter. For the purposes of this discussion, I will only consider a gas—more specifically, a perfect gas—because temperature and density are clearly defined. The equation for a perfect gas is as follows: #PV=k_bNT# where #P# is the pressure, #V# is the volume, #k_b# is a the constant of Boltzmann, #N# is the number of particles and #T# is the temperature. The density can be defined as the number of particles per unit of volume #\rho=N/V#. If we consider that the pressure stay constant, then we have #TN/V=P/k_b# #T=K/\rho# where #K# is the constant quantity #K=P/k_b#. As a result, the temperature is inversely proportional to density, which implies that as density rises, temperature falls and vice versa.

Declan Carroll · Answer

undefined The relationship between temperature and density of matter is based on the thermal expansion and contraction of materials; a rise in temperature generally causes the density of matter to decrease, while a fall in temperature generally causes the density to increase.