Final answer:
An object with more particles generally has greater thermal energy than one with fewer particles because thermal energy is the sum of the kinetic energy of all the particles, and more particles result in more motion and energy.
Step-by-step explanation:
If an object has more particles, its thermal energy is generally greater than an object with fewer particles. This is because thermal energy is the sum of the kinetic energies of all the particles within an object, and more particles typically mean there is more motion to account for.
Thermal energy is the energy associated with the motion of particles in a substance. When particles collide, the one with greater kinetic energy transfers some of its energy to the one with less, causing a net transfer of heat from warmer to cooler bodies. The total internal energy of a system, which includes thermal energy, depends on the kinetic and potential energies of the atoms and molecules within it.
Thus, thermal energy increases with both the average velocity of the particles and the number of particles. Simply put, if you heat up a larger amount of substance to the same temperature, it will contain more thermal energy than a smaller amount, because there are more particles contributing to the total energy.