What experience shows that during the transition of internal energy from one body to another, its value is preserved?

The experience of mixing water of different temperatures is a good example of the transfer of internal energy from one object to another, in which the total energy of the system is saved.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.