Endothermic vs Exothermic Reactions Mrs Chan Energy Energy

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. 2

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. 3

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. 4

Endothermic Processes • Any change in matter in which energy is absorbed from the surroundings to the system is an endothermic process. 5

Endothermic Process Examples Physical Changes The melting of ice Chemical Changes The reaction between barium hydroxide and ammonium nitrate The boiling of water 6

Exothermic Processes • Any change in matter in which energy is released from the system to the surrounding is an exothermic process. 7

Exothermic Process Examples Physical Changes The freezing of water Chemical Changes The explosive reaction between hydrogen and oxygen to form water The condensation of water 8

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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. 10

• Conservation of Energy in a Chemical Reaction 11

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. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. 12