Increase in cloth's mass When we iron our clothes does the mass of the cloth increase, since energy transformation and transfer happens, Einstein's energy mass relation comes to action and causes increase in mass.
Am I right or wrong?
 A: Assume that we started with a dry cloth, use a dry iron (no steam) and don't initiate any chemistry (you don't want to burn the collar, after all).
There are two way to look at this.


*

*On a macroscopic scale the cloth (taken as a whole) has gained internal energy, so it simply is more massive. No "transformation" is required. The energy exists in the more energetic bounds between atoms and molecules and that is mass. Just as the proton is mostly binding energy rather than the (very small) rest energy of the valence quark content.

*On the microscopic scale the heat ends up almost entirely in thermal motion of existing molecules without changing or exciting the molecules. So the molecules have the same mass they did before.
If you have excited some of the molecules than those molecules (taken as a whole) are more massive than before, but their unexcited atoms are not. And so on, up and down the energy/distance scales.

Aside: There seems to be a lot of misunderstanding about this. There is no magic which transforms energy from "energy" into "mass". Energy in internal degrees of freedom acts as mass as long as the physics you are interested in can't probe those internal degrees of freedom. When you can probe a particular scale you become able to separate the kinetic energy of the components and their interaction energy and their mass (which may consist partly of binding energy of smaller components, too).
