The Thermodynamics of Hand Warmers

Name: The Thermodynamics of Hand Warmers
Brand: Flinn Scientific
SKU: PF2051

Item #: PF2051

Price: $50.00

In this lab experience, students investigate the energy changes that accompany the dissolution of common laboratory salts in water and apply the results to design a hand warmer that is reliable, safe and inexpensive. Based on temperature measurement results, students will determine that dissolution of NaOH and CaCl2 releases heat energy, whereas dissolution of NaCl and NH4Cl absorbs heat from the surroundings. Then they will explain the results, based on differences in the strength of ionic bonds in the solid compounds, intermolecular water forces, and the interactions between ions and water molecules in solution. Finally, students will propose the design of hand warmers using a solution of CaCl2 or NaOH in water and instant cold packs using aqueous NH4Cl.

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Safety: Before conducting the lab, review the safety precautions on the student page with the class. Then discuss any safety precautions that are specific to your science laboratory or classroom. Safety glasses, a lab coat, and gloves must be worn at all times. Calcium chloride and ammonium chloride are slightly toxic. Sodium hydroxide is corrosive to body tissue, especially eyes and skin.

Materials Included in Kit

Consumable:
Ammonium chloride, 350 g
Calcium chloride, 300 g
Sodium chloride, 300 g
Sodium hydroxide, 500 g
Polystyrene cups, 20
Weighing dishes, 50

Additional Materials Required
Beakers, Borosilicate Glass, 250-mL, 10
DLAB Classic Magnetic Stirrer/Hot Plate, 10
Flinn Digital Thermometer, 10
Flinn Scientific Electronic Balance, 410 x 0.01-g, 10
Gloves, Terrycloth, General Purpose, 10
Ring Support, with Rod Clamp, 4", 10
Support Stand, 6" x 9", 10
Student Timer, 12-pack, 1
Cylinder, Borosilicate Glass, 100 mL, 10

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