Endothermic vs Exothermic Reactions Mrs. Chan

Energy Energy is the capacity to do some kind of work, such as moving an object, forming a new compound, or generating light. Energy is always involved when there is a change in matter.

System and Surroundings The universe is divided into two parts: The SYSTEM is the part of the universe on which to focus attention. The SURROUNDINGS includes everything else in the universe.

All physical and chemical changes involve a change in energy. Every Change in Matter Involves a Change in Energy All physical and chemical changes involve a change in energy. Some involve releasing energy, some involve absorbing energy.

Endothermic Processes Any change in matter in which energy is absorbed from the surroundings to the system is an endothermic process.

Endothermic Process Examples Physical Changes Chemical Changes The melting of ice The boiling of water The reaction between barium hydroxide and ammonium nitrate

Exothermic Processes Any change in matter in which energy is released from the system to the surrounding is an exothermic process.

Exothermic Process Examples Physical Changes Chemical Changes The freezing of water The condensation of water The explosive reaction between hydrogen and oxygen to form water

The Law of Conservation of Energy Energy can be absorbed by the surroundings or released to the surroundings, but it cannot be created or destroyed. The law of conservation of energy states that during any physical or chemical change, the total quantity of energy remains constant.

Conservation of Energy in a Chemical Reaction

Temperature vs Heat Temperature – Measure of the random motions (average kinetic energy) of the components of a substance. Heat – Flow of energy due to a temperature difference.