Exothermic and Endothermic Chemical Reactions All chemical reactions involve bond breaking and bond forming. Energy is needed to break bonds and energy is released when bonds are formed. Chemical reactions are accompanied by a change in energy, mainly in the form of heat. A reaction is EXOTHERMIC if more energy is RELEASED than SUPPLIED. If more energy is SUPPLIED than is RELEASED then the reaction is ENDOTHERMIC www.makemegenius.com Free Science Videos for Kids

1. Exothermic Reactions A reaction in which heat is released The temperature in the system increases C (g) + O2 (g)  CO2 (g) + 393.5 kJ Heat reaction ΔH = -393.5 kJ Heat Heat

2. Endothermic reactions N2(g) + O2(g) + 180.5 KJ →→ 2NO(g) N2(g) + O2(g) + 180.5 KJ →→ 2NO(g) N2(g) + O2(g) + 180.5 KJ →→ 2NO(g) 2. Endothermic reactions A reaction in which heat is absorbed by the reactants The temperature in the system decreases N2(g) + O2(g) + 180.5 KJ → 2NO(g) ΔH = + 180.5 KJ Heat

www.makemegenius.com Free Science Videos for Kids Examples Exothermic Combustion of fuels Yeast & Hydrogen Peroxide Epson salts & water Endothermic Photosynthesis Acedic Acid & Sodium Bicarbonate www.makemegenius.com Free Science Videos for Kids © Teachable . Some rights reserved. http://teachable.net/res.asp?r=1910