1. The problem statement, all variables and given/known data Think about forces between molecules, and explain why we might expect B(cm^3/mol) to be negative at low temperatures but positive at high temperatures. 2. Relevant equations 3. The attempt at a solution Well at low temperatures the motion of particles are not as high as they would be at high temperatures, so there is less kinetic energy so wouldn't they attract each other and opposite charges attractive but the product of two different charges are negative. As the temperature increases, the kinetic energy increases and attrative intermolecular forces begin to break apart and therefore a repulsive forces arises between the particles. Therefore the charges of the particle either must be both positive or both negative , therefore the product of the charges of the two particles are positive.