The sum of the energy of a substance is the sum of the kinetic energies and potential energies of all of the molecules in the substance.

word missing in your sentence is "Mechanical"

Explanation:

The mechanical energy of a body is defined as the sum of kinetic energy plus potential energies.

The kinetic energy due to the movement and depends on the velocity squared

Potential energy is a configuration energy and the relative position of the body depends on another arbitrary point where this energy is taken as zero

 Therefore the word missing in your sentence is "Mechanical"