Does heating a body increase its mass?

[Robin04]

Does the mass-energy equivalence mean that if we heat a body then its mass will increase?

 

[CWatters]

Yes. Google will find an explanation.

 

[CWatters]

I should add it's a very small effect. E=mc^2 so m=E/c^2 and c is big.

 

[Robin04]

So this means that the mass is not only dependent on the quantity of matter in that object, right?

 

[weirdoguy]

Well, I think it's hard to strictly and generally define what "quantity of matter" is. I would say that is a good non-relativistic heuristic about what mass is. In relativistic physics mass is defined by $$m=\frac{1}{c^2}\sqrt{E^2-p^2c^2}$$
E and p are of course frame-dependent, but it turns out that m is not, so it is a good and non-problematic generalisation of Newtonian mass. Contrary to what is known as "relativisitc mass"...

 

[anorlunda]

Have a look at this article.
https://en.m.wikipedia.org/wiki/Invariant_mass

Warning, some of that article is more advanced than B level.