Internal energy (U) is defined as the total energy of a closed system. Internal energy is the sum of potential energy of the system and the system's kinetic energy and the internal energy of a system can be increased by introduction of matter, by heat, or by doing thermodynamic work on the system.
B. adding heat to the system and having the system do work on the surroundings
Explanation:
The internal energy of a system is the energy contained within the system. From first law of thermodynamics we have the equation : dq=du+dw
and we know that energy can neither be created nor destroyed; energy can only be transferred or changed from one form to another therefore du is zero. dq = dw this means that the entire heat supplied is converted into work (on the surroundings)
However, some of the heat supplied is also used to increase the internal energy of the system
If the half-life of 14C is 5730 years, when this period of time has passed it will have been halved, it is called the exponential decay law of radioactive isotopes.
