# Mass and Density relationship

1. May 24, 2010

### jaketodd

Are mass and density always in a 1 to 1 relationship? For example, can there be a material that takes up more space without it having more mass than another material that takes up less space?

Thanks,

Jake

2. May 24, 2010

### Staff: Mentor

I can't parse your English. Can you rephrase the question?

3. May 24, 2010

### TheAlkemist

*edit*
Yes. Ice vs water. When water freezes (to ice) it increases its volume (space) by about 9% due to the "open lattice" crystal structure.

Last edited by a moderator: May 4, 2017
4. May 24, 2010

### jaketodd

If an object has mass X, then can there be another object, also with mass X, which takes up more space than the first object?

5. May 24, 2010

### jaketodd

Ok, so a unit of water is smaller than if you freeze that water, but does the ice actually take up more space, not just the dimension lengths of the object, but taking up more space (more matter per unit area)?

6. May 24, 2010

### TheAlkemist

What do you mean by "dimension lengths"?

Last edited: May 24, 2010
7. May 24, 2010

### jaketodd

The length, width and height of the object.

8. May 24, 2010

### pallidin

Take some water and have 1-ounce remain liquid, while a second(separate) ounce is frozen.

They both weigh the same(same mass), but the frozen ounce has greater volume and less density than the liquid sample.

9. May 24, 2010

### jaketodd

This may clarify my question:

Under any circumstances, can something block more photons, for example, than something that has more mass?

10. May 24, 2010

### Staff: Mentor

Of course: otherwise all objects would have the Sam density.

11. May 24, 2010

### Integral

Staff Emeritus
A kg of Al vs a kg of Iron? Or the other way round, compare the mass of 1cm3 of Al vs the mass of 1cm3 of Iron.

Could you try to be a bit more specific in your question.

12. May 24, 2010

### Integral

Staff Emeritus
Please try to figure out just what you are asking. A m2 of card board has a much bigger shadow then a similer mass of iron or any other metal.

13. May 24, 2010

### Ali Inam

Obviously, the mass will remain the same

But the volume cant be the same if you are considering water and ice

So,

Density may change

14. May 24, 2010

### vaibhav1803

$$M=\oint\rho \partial V$$

...it isnt allowing latex preview so theres supposed to be a volume element
$$\partial V$$ in there in case its missing.

for a constant density case,

$$M =\rho V$$

the rest i believe you can figure out yourself...through the equation

15. May 24, 2010

### jaketodd

Perhaps a material where all the molecules are polarized and facing the same direction compared with a material with the same number of molecules but forming structures that wouldn't let as many photons through? In this example, the two materials would have the same mass. Is this possible?

Thanks,

Jake

16. May 24, 2010

### vaibhav1803

completely possible, any reason why it shouldn't happen?

17. May 24, 2010

### jaketodd

Anyone?

18. May 24, 2010

### Staff: Mentor

Obviously yes. Consider a 1 kg piece of lead and a 1 kg piece of Styrofoam.

I think you are not asking what you really want to know. Please try to think your question through a bit better.

19. May 26, 2010

### TheAlkemist

OK. I might get what you're asking here. I think it's a question of substance and form.

Substance:
The mass of an object is equal to the sum of the masses of all the atoms/molecules that make it up.

Form:
The form a material assumes depends on the nature of the interactions between the atoms/molecules that it's made of. Between the interacting atoms/molecules is "space", the amount of which essentially determines the density of the material.

The way a material interacts with photons certainly depends on how the atoms/molecules are arranged.

DaleSpam explains this above with lead and Styrofoam.