The diagram below shows the different phase transitions that occur in matter.
 Three bars are shown labeled Solid, Liquid, and Gas. They are connected by arrows labeled 1 to 6. Arrow 1 points from liquid to gas; arrow 2 from solid to liquid, arrow 3 from solid to gas, arrow 4 from gas to liquid, arrow 5 from liquid to solid, and arrow 6 from gas to solid.
 Which best describes the process that arrow 1 represents?
 Molecules are speeding up during boiling.
 Molecules are depositing as ice on a surface.
 Molecules are slowing down during condensing.
 Molecules are moving from stationary positions.