What type of reaction occurs without being started by some outside force a. spontaneous reaction b. physical reaction c. activation energy reaction d. backward reaction

Liquid water turns into water vapor at which step in the water cycle

Which best explains how a heat pump can heat a room? cold air from the house is moved through pipes, where it absorbs thermal energy. warm air from outside is pushed into the house to replace the cold air. combustion warms the air when chemical energy is transferred to thermal energy. fuel is used to move a piston, which pushes warm air into the house.

Diagram of the evolution of land plants?