Chemical Reactions and Energy You will be learning: 1.How to identify the source of energy changes in chemical reactions. 2.To compare and contrast exergonic and endergonic reactions. 3.How to examine the effects of catalysts and inhibitors on the speed of chemical reactions.

More Energy Out Exergonic reactions – Less energy is required to break the original bonds than is released when new bonds form. – Energy may be in the form of light or heat. – Examples: glow sticks or heat packs.

Exothermic Reaction – When heat is the primary form of energy given off. – Exo- prefix means “outside” – Thermic base word means “heat” – Burning, explosions

More Energy In Endergonic reactions – When the chemical reaction requires more energy to break bonds than is released. – Absorbs light, heat, or electricity – Example: cold pack

Endothermic Reaction – When the chemical reaction absorbs more heat than is given off. – Endo- prefix means “inside” – Thermic base word means “heat”

Catalysts and Inhibitors Catalysts – a substance that speeds up the rate of the chemical reaction without changing itself – After the chemical reaction you can take out the catalyst and have the same amount of catalyst that was originally put in. – Catalytic converters in the cars exhaust system changes harmful waste products into more inert by products faster. Inhibitors - a substance that slows down the rate of the chemical reaction – Food preservatives, salt, spices

A reaction that releases energy is called an _____ reaction exergonic

A reaction that absorbs energy is called an ____ reaction endergonic

Thermic means ____. heat

Thermic means _______.