GK-12 Sensors!
Portable Module

Title: Endothermic/Exothermic Reactions

Author: Michael Lewark

Discipline: Chemistry

Introduction

An exothermic reaction produces heat, and endothermic reactions absorb heat from the surroundings. During an exothermic reaction, more energy is produced from the formation of new bonds than energy is required to break existing bonds. The surplus of energy that is released is lost as heat.

The opposite is generally true for a reaction which is endothermic. More energy is required to break existing bonds than is released when new bonds are formed. The shortfall of energy is absorbed from the surroundings and a cooling effect can be measured.

Associated Maine Learning Results

H. ENERGY - SECONDARY GRADES - 9.
Demonstrate an understanding that energy can be found in chemical bonds and can be used when it is released from those bonds.

Required Equipment

• TI CBL
• TI86
• Vernier temperature probe
• 250mL beaker
• Styrofoam cup

Suggested Chemical Combinations

For exothermic reaction:

• 30 mL of 6 M HCl solution + a piece of magnesium metal
• 20 mL of concentrated Sulfuric Acid + 50 mL of water

For endothermic reaction:

• 10 g of solid baking soda + 30 mL of citric acid solution
• 16 g Ammonium Thiocyanate + 32 g Barium Hydroxide
• 25 g ammonium nitrate + 250 ml of tap water

Procedure

See PDF document.

Expected results

The exothermic reaction will get warm and the endothermic reactions will get cold.

Troubleshooting

Any problems with the CBL usually can be corrected by referring to its manual. If the reaction is not dramatic enough check whether the proper amounts of chemicals were used.