Density difference of the same substance?

Density wouldn’t change in that situation. However density would change if the state of the material changes.

It could vary if it’s a compressible substance. On earth, the atmospheric pressure would shrink it, so it would become denser.

@thorninmud True, I was thinking about something like metal, when its solid its deser than when its a liquid, but a compressable substance would beaffected.

Think of a comparison: would English grammar be the same on the moon as on earth?

Thanks a lot to all of you! So, with a change in its chemical conditions, it would be comprehensible, if there is something changing. That’s what I was hoping to expect.

@XOIIO: If I would compare my English grammar skills dependent on the location, I believe it wouldn’t make any difference for me as a German native speaker (although that is no excusion, but at least my good will for trying).

Yes, as things become more compressed as the gravitational field increases.

Yes. Smush many things and they become more dense. Gravity can smush things. Air pressure can smush things. Air pressure and gravity are different on Earth versus the Moon.

@martzel86: …with a change in its chemical conditions, it would be [compressible]... I’d say physical, not chemical, conditions.

The effect of air pressure (which arises in the first place from gravitation) would only change the density of gas-filled objects like balloons or certain foams. Gravity itself should have no effect on density except for objects immense enough to experience tidal forces, which would tend to decrease density by outward tension.

In comparing earth and moon, note that (1) the moon’s gravity is 1/6 that of earth; and (2) the moon has no atmosphere, so its “air pressure” is always zero.

Permit me to quote from Wikipedia’s article on density:
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In general, density can be changed by changing either the pressure or the temperature. Increasing the pressure always increases the density of a material. Increasing the temperature generally decreases the density, but there are notable exceptions…

The effect of pressure and temperature on the densities of liquids and solids is small. The compressibility for a typical liquid or solid…roughly translates into needing around ten thousand times atmospheric pressure to reduce the volume of a substance by one percent.
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Note that the atmosphere on Venus, whose gravity is about 90% of earth’s, is almost 100 times that on earth—equivalent to diving in the ocean to a depth of 1 kilometer. Even at this crushing pressure, however, density would (according to quote above) only increase by 1/100 of 1% = a factor of 0.0001.

@Zaku I will now have to use the word “smush” on a physics term paper some day.

@thorninmud, think of density as the number of things in a given volume. If I have a 1m x 1m x 1m box with 10,000 marbles in it, the density of marbles in that box would be

ρ = n / V = 10,000 / m^3.

Since the actual definition of density requires a mass value instead of a dimensionless number, the compressed substance would have a greater mass in an equal volume.