Does heat affect the mass of an object?

[treeelf5150]

Recently our Physics teacher did a demo with us on anodes and cathodes to determine the electric charge on an electron. During a certain part of the demo, he had to dry the copper cathode to determine the difference in weight. He then told us it was very important tat he waited until the copper had cooled before he massed it again. He asked us why, but none of the class could figure out why. So he told us to go home and research it on the internet. I have been, but I have seen both yes's and no's about whether the temperature would affect the weight. Can someone explain to me why ou would have to wait to weigh the copper again?

 

[Jewish_Vulcan]

Consider my idea, Maybe it is because E=MC^2, tempature is a measurement of kinetic energy and heat is the flow of thermal energy so they are all related. So if you increase the tempature or TE then would it not cause the mass to decrease? Do not believe me without verifaction though because I have only used the E=MC^2 equation to calculate binding energy, I am not too familiar of its applications. Furthermore I know that the specific heat of an object is based off its mass and other properties, here is the equation for specific heat capacity
C(specific Heat Capacity)=Q(heat in joules)/M(mass kg)*ChangeTemp(Kelvins or Celcius)
but the equation would not explain the mass changing, it assumes that the mass is constant for that heat capacity and describes "how much energy it would take to heat 1kg of a substance by one kelvin or celcius")

 

[treeelf5150]

Consider my idea, Maybe it is because E=MC^2, tempature is a measurement of kinetic energy and heat is the flow of thermal energy so they are all related. So if you increase the tempature or TE then would it not cause the mass to decrease? Do not believe me without verifaction though because I have only used the E=MC^2 equation to calculate binding energy, I am not too familiar of its applications. Furthermore I know that the specific heat of an object is based off its mass and other properties, here is the equation for specific heat capacity
C(specific Heat Capacity)=Q(heat in joules)/M(mass kg)*ChangeTemp(Kelvins or Celcius)
but the equation would not explain the mass changing, it assumes that the mass is constant for that heat capacity and describes "how much energy it would take to heat 1kg of a substance by one kelvin or celcius")

yes, that sort of makes sense, I was thinking maybe it doesn't increase the mass, but the weight? Also maybe something to do with conduction waves... I'm not sure, he's supposed to tell us the next time we meet for class but it's just itching at me I wanna know why

 

[Jewish_Vulcan]

yes, that sort of makes sense, I was thinking maybe it doesn't increase the mass, but the weight? Also maybe something to do with conduction waves... I'm not sure, he's supposed to tell us the next time we meet for class but it's just itching at me I wanna know why

I know the feeling haha, remember Fweight=M(mass kg)*G(gravity 9.81m/s^2 on earth), so if mass increased Fw would increase. If we are not in a vacuum then convection currents could cause the mass to change. Please describe the setup of the experiment in more detail, what happened before and then after the change in mass?