1. Entropy statement: Whenever a spontaneous process takes place, it is accompanied by an increase in the total entropy of the universe”.
2. Kelvin-Planck statement: it is impossible to take heat from a hotter reservoir and convert it completely into work by a cyclic process without transferring a part of heat to a cooler reservoir.
3. Efficiency statement: Even an ideal, frictionless engine cannot convert 100% of its input heat into work.
4. Clausius statement: Heat flows spontaneously from hot objects to cold objects and to get it flow in the opposite direction, we have to spend some work.
