# What expands when an element heats up?

Two part question - Not sure if this is Physics based or Chemistry though, maybe both.

Quite simply, if I warm up a gram of mercury (I use mercury for its obvious reaction to heat), it will expand. What part of the mercury is expanding? Is it the space between the atoms, or the Atoms themselves?

If its the space between the atoms, then what fills the gap?

I`m confused. Thank you.

Update:

@ Retsum - What space? A vacuum? if so then what keeps it from imploding back in?

Or is the energy of the heat simply converted to mass as in e=mc2 what expands the element until its cooled and the energy (and therefore the mass) reduced?

Update 2:

m=e/c2 i mean.

Update 3:

2 excellent answers there. Narayans was the closest to resoving my issue. I am mildly familier with the anomaly of `dark matter and its counter part `dark energy`. My question was specifically the on a molecular level. Its the energy itself expands the element. The space in between is a vacuum. I think i`ve got it! Einsteins equation has very little to do with it, though i guess if you heated an element it would gain a tiny amount of mass due to the 2 being one of the same. Maybe i should ask another question about that.

Relevance

as you heat something up, particles gain kinetic energy, they move faster and faster. now lets take a solid and heat it up, as particles or molecules vibrate faster, they cover more distance and take up more space, the particle itself doesn't enlargen, it is all the particles together taking up more space which causes the whole solid to take up more space.

nothing fills the gap, empty space does.

if you meant what "keeps space in BETWEEN partices from imploding", then this is easy, imagine the particles vibrating, the kinetic energy of these particles is what keeps it from imploding. space is trying to be filled actually, ie, particles are trying to hold each other together, but as you heat the particles up, the kinetic energy that they gain starts to oppose the forces that are trying to keep particles together.

In other words, the solid is trying to implode and become as small as possible but when you heat the solid, particles in it gains kinetic energy and starts moving with a force large enough to oppose the force that is trying to make it implode.

good question..

what you said is interesting.

but if u meant "what keeps space from imploding ie the space all around us in the universe" then

now look at this, why is the space expanding, shouldnt gravity of all the matter in space supposed to slow the expansion, shouldnt the gravity of all matter pull every thing together, but instead every thing (ie galaxies) is moving further away from each other faster and faster, because there is something that is opposing the gravitational pull of the galaxies on each other, this is what we call dark energy and humans are just learning about, this is what keeps space from imploding.

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