Energy that flows from an objective with a higher temperature to an object with a lower temperature

Gunpowder residue is most likely to show up where on a shooters hands

What are atoms of the same element with varying number of neutrons

Oxygen undergoes an isentropic expansion from 120 degree c and 280 kpa absolute to 140 kpa absolute. determine the final temperature of the oxygen and the amount of work per kg of o_2 produced in the process if it is adiabatic.