Why do people act like they are your friends, then talk and whisper behind your back to another?

it's just the way of people, of course there are some that don't but a lot of us have a tendency to want to fit in. If there with a group of friends that don't like you most people will talk behind your back to fit in with that group. Either that or their just fake and simply never liked you to begin with

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.