Predict the energy trend as a substance changes from a solid to liquid to gas on this graph. A) It would increase from bottom left to top right. B) It would decrease from top left to bottom right. C) It would be a horizontal line as energy would remain constant. D) It would increase from solid to liquid, then decrease from liquid to gas.

Which of the following best describes internal energy? a. the difference between the kinetic and potential energies of the particles in a system b. the sum of the kinetic and potential energies of the particles in a system c. the sum of the kinetic and thermal energies of the particles in a system d. the difference between the kinetic and thermal energies of the particles in a system