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?