1. 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
Free Science Videos for Kids

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

3. 2. Endothermic reactions
N2(g) + O2(g)  KJ →→ 2NO(g)
N2(g) + O2(g)  KJ →→ 2NO(g)
N2(g) + O2(g)  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)  KJ → 2NO(g)
ΔH = KJ
Heat

4. 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
Free Science Videos for Kids
© Teachable . Some rights reserved.