The atoms in a liquid state of matter have a definite volume, eventhough they acquire the shape of the container that contains them, the volume will always be the same, while in a solid the shape and volume will remain constant, on the other hand for a gas, the substance will fill the container where it is, having different volumes.
Potential energy diagrams represent the energy transfer in chemical reactions in a diagram called a potential energy graph and/or a reaction progress curve. A potential energy diagram shows the adjustment in potential energy of a system as reactants are changed.