If a system absorbs 155.0 kJ of heat from its surroundings and the system does 45.0 kJ of work on its surroundings, what is the change in the internal energy of the system, in kJ

The air that we breath is made mostly of which gaseous molecule

Since the energy was not raising the temperature of the water during these segments, what was the energy used to do instead? your answer must include an explanation of what is happening to the molecules.

Two identical stars with mass m orbit around their center of mass. each orbit is circular and has radius r, so that the two stars are always on opposite sides of the circle. (a) find the gravitational force of one star on the other. (b) find the orbital speed of each star and the period of the orbit. (c) how much energy would be required to separate the two stars to infinity?