When thermal energy is applied to a substance, its atoms or molecules gain kinetic energy.
Thermal energy refers to the total energy possessed by the atoms or molecules within a substance due to their random motion. This motion is often described as thermal motion or kinetic energy. When heat is added to a substance, such as by heating it, the energy is transferred to the particles, increasing their kinetic energy.
As the substance's temperature rises, its atoms or molecules gain more kinetic energy, leading to increased movement and faster vibration or rotation. This increase in kinetic energy is responsible for raising the overall temperature of the substance.
Conversely, when a substance loses thermal energy, its atoms or molecules lose kinetic energy, resulting in a decrease in temperature. This can occur through processes such as cooling, where heat is transferred from the substance to its surroundings, causing the particles to slow down and reducing their kinetic energy.
In summary, the application of thermal energy causes the atoms or molecules in a substance to gain kinetic energy, while the loss of thermal energy leads to a decrease in their kinetic energy.