In phase change cycles and engines, the working fluids are gases and liquids. The engine converts the working fluid from a gas to a liquid, from liquid to gas, or both, generating work from the fluid expansion or compression.
*Rankine cycle (classical steam engine)
*Regenerative cycle (steam engine more efficient than Rankine cycle)
*Organic Rankine cycle (Coolant changing phase in temperature ranges of ice and hot liquid water)
*Vapor to liquid cycle (drinking bird, injector, Minto wheel)
*Liquid to solid cycle (frost heaving – water changing from ice to liquid and back again can lift rock up to 60 cm.)
*Solid to gas cycle (firearms  – solid propellants combust to hot gases.)