What is the process called when a gas turns back into a liquid

Porque crees que el agua no podia subir mas de 10 m de altura con ese tipo de bomba

What does si stand for,when referring to a system of measurement

Six pendulums of mass mand length las shown are released from rest at the same angle theta from vertical. rank the pendulums according to the numberof complete cycles of motion each pendulum goes through perminute. a. l= 1m m=2kg b. l= 4m m=1 kg c. l= 2 m m= 2 kg d. l= 1 m m= 4 kg e. l= 2 m m = 4 kg f. l= 4m m = 4kg