Hi, I am having a hard time understanding this concept. I know that the problem is isoberic because it has constant pressure. I also know we use w=-PdeltaT , but I missing a certain relationship with temperature. I know for internal energy is at equilibrium temperature and pressure are both equal. an we find internal energy by U=Q+W. Please help I dont know how else to attack the problem???

1)What mass of helium requires 40.0 J of work to be done on it at a constant pressure

to change its temperature from 250 K to 350 K?

2)What is the change in internal energy of a 25 g sample of water as it is converted to

steam at 100C at a constant volume?

3)How much entropy is gained during the previous process?