Simplify the following text for a Grade 9 native English-speaking person.
Original: Thermal energy is also often used as a property of single particles to designate the kinetic energy of the particles . An example is the description of thermal neutrons having a certain thermal energy , which is meant as the kinetic energy of the particle that is equivalent to the temperature of its surroundings .
Simplified: In thermal physics , thermal energy is the type of energy that has a system that increases with its temperature .