7. De acuerdo con esta clasificación, no es un hidrocarburo A. CH3-CO-CH3 B. CH4 C. C6H6 D. CH3-CH2-CH3 8. No se considera como compuesto orgánico A. Plásticos B. Dióxido de carbono C. Almidón D. Tejido óseo

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.