If I heat up a material, does it gain weight according to E=mc2?

Question

The heated material has more energy than before, so does it weigth more?
I know the gain would be very very very small, but does this happen? m=E/c2

Answer 1

Yes.

You add energy ΔE,
you gain extra mass Δm = ΔE/c², and
you gain extra weight ΔW = Δmg = gΔE/c².

More accurately, the rest mass of heated body increses because its energy E increases, but momentum remains the same (it gains energy while remaining at rest).

Answer 2

I don't know about you, but I feel fat when I get on an airplane. It must be my increased potential energy being turned into mass......











/sarcasm.
Don't you just hate it when people take relativity and its concepts out of context? I do.

By the way I'm with Garret J on this one, you're increasing its THERMAL energy. The only way to increase its mass is to add KINETIC energy. Thats what relativity is about, it makes no mention of thermal energy. The E=mc^2 comes from the more complete formula E^2 = (pc)^2 + (mc^2)^2, where p is momentum. If the material is at rest, then the equation reduces to E=mc^2.
You're not doing any conversion by adding heat to the material.

RickB: You're right, you got me on the thermal energy part, I faileded to think about it that way. However, I'm still not satisfied that by adding heat to a material, you're increasing its mass. Einstein's equation says that if you have so and so energy, it is the equivalent of so and so mass, but you have to CONVERT it from one form to the other first through some sort of a nuclear reaction, or maybe another way I'm not familiar with.
Just having heat or other energy around does not automatically equal mass, I still don't see how adding heat to a material will automatically increase its mass, yes you're increasing its thermal energy and the molecules of that material will move around faster, causing the material to expand and even change states, but the mass will remain the same since there's no conversion going on and the chemical composition stays the same. 1 gram of ice is still equal to 1 gram of water, and they're still H2O.
So far the only ways I know of that we can convert mass to energy is by nuclear fusion or fission which completely changes one atom to another, and I have no idea if we have even found a way to convert energy into mass, at least none that I know of besides say accelerating a particle to relativistic velocities.

But, I'll ask one of my professors tomorrow and see what he says.

Answer 3

Yes, its weight increases. One way to look at this is: as you heat it up, the molecules move faster, and (according to relativity) motion causes mass to increase.

Garret J is mistaken when he says that E=mc² "...only applies to CONVERTING energy to mass and mass to energy." In fact, the formula implies that WHENEVER your energy increases, so does your mass, and vice versa. When you're riding in a fast car, you have more mass than when you're sitting still.

To HRH The Fresh Prince: Thermal energy IS kinetic energy! The molecules are moving faster.

Answer 4

The relativistic (inertial) mass of the atoms contribute to the rest mass of the object. The rest mass of an object is the sum total of its internal energy / c^2 ... period. There is no "conversion" required. What is it about "equals" that some people don't understand?

Answer 5

Yes, if you pump energy into an object, its mass is bound to increase according to that formula. Conversely, when energy leaves the confines of the object, its mass drops. This applies to any radioactive decay, for example.

Answer 6

i would say no
because energy does not have mass, it is not mass.

You can turn mass into energy and energy into mass
i believe e=mc2 to be expression as to how much potential energy is in mass and how much potential mass in energy

other wise all heavy(relatively hi mass) objects would be hot

if you heated it up the mass would go up an temperature down

Answer 7

No. It gains energy, but the formula:

E = m * c ^2

only applies to CONVERTING energy to mass and mass to energy. You're not doing any conversion there. You're simply adding to the thermal energy of the material. If there were some way to convert the thermal energy INTO matter, then it might gain mass, but I can't think of anything that would do that.

Answer 8

Yes. relatily