Develop a textel adrop of water is made up of his substances. one substance is
open. the second substance is called oxygen. the smallest particles of water
o n are up of parts hydrogen and one part exygen write a formula for
the smallest part of water. stet by wing symbols for hydrogen and oxygant)

Which of the following statements is true? a. most heat energy is easily recovered and used for useful actions. b. friction causes molecules to vibrate more slowly. burning air and gasoline in an c. engine changes chemical energy into mechanical energy. it is impossible to d. change mechanical energy into mechanical energy.