# Can we relate volume to amount of matter?

Is volume the amount of matter in a body?If so, one kilogram water should have the same volume in its gaseous form. If we think of it, there is more space between the molecules of water in gaseous form, so some would say that the volume of water in gaseous form is more than the volume of water in liquid form. But we should ignore the the intermolecular space and only count the space occupied by the atoms. Since the number of atoms is constant therefore volume should be constant.Am I right?

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## 2 Answers

Volume is not really about the amount, but about the space occupied. Let's perhaps stay at the macroscopic quantities to make the things easier to understand. We'll see that the concepts roughly translate to microscopic quantities as well.

Consider that I have one cup of lightly packed flour. The volume occupied is one cup, and the flour in the cup has some mass. Now, if I pack some more flour into the cup (suppose you press hard), the volume will stay the same, but the mass (or the amount of atoms in the cup) will change.

Atoms too have different sizes, depending on its type. For instance, a plutonium atom is about three times the size of a hydrogen atom. But it's 244 times heavier and contains 94 protons (hydrogen contains just one)! So the volume does not scale proportionally to the "amount of matter" (if by "matter" you mean elementary particles within the atom), as you put it. We're not even dealing with multiple molecules here, but individual atoms, yet we fail if we try to link these two quantities.

Remember that $V=\frac{m}{\rho}$, volume is proportional to the mass divided by its density.

(perhaps this would be more suitable for a comment)

Volume measures the area.
Matter simply put, is a measurement of particles that have mass in the object at rest.
Density is the mass of the object divided by its volume.

Is volume the amount of matter in a body? So No is the Answer :)

If I follow your question you might be interested in how the the Ideal gas law describes gases.

PV=nRT

This equation looks at how (V)Volume, (P)Pressure and (T)Temperature are related With an amount of a matter.