1. what is the difference between mechanical advantage and efficiency?

Mechanical advantage is a measure of how much your force is multiplied, efficiency is a measure of how much of the work you do actually goes to moving the thing you're trying to move.

Consider a system of pulleys used to lift a heavy load: the pulleys provide a mechanical advantage to let you lift the load more easily, but in addition to moving the load, you also have to move the rope and the pulleys. 

Adding more pulleys may increase the mechanical advantage, but it also increases the amount of  extra stuff you're moving. 

The more extra stuff you're moving, the less efficient the system.

Evaporation: this is when warmth from the sun causes water from oceans, lakes, streams, ice and soils to rise into the air and turn into water vapour (gas). water vapour droplets join together to make clouds! condensation: this is when water vapour in the air cools down and turns back into liquid water.