The statement 'The more particles a substance has at a given temperature, the more thermal energy it has' is true. The kinetic molecular theory of gases has three main laws and one of them is the average kinetic energy of the particles in a gas. The average kinetic energy of the gas particles is the behavior and movement it does in the surroundings. It is directly proportional to temperature wherein if you increase the temperature, the kinetic energy of a particle also increases. It will also decrease its movement or its kinetic energy if the temperature lowers.