By Mike Isley
Produt Developer

Water is an amazing liquid. Not only is it the main solvent of cellular protoplasm, it also helps moderate climates with its high heat capacity. Water absorbs a large quantity of heat and slowly releases it over a period of time. This is the reason coastal climates are more moderate than climates farther inland. Water’s specific heat capacity—the amount of heat needed to raise a gram by a degree Celsius—is 1 cal/g ^oC. On the other hand, quartz sand has a much lower specific heat capacity of only 0.2 cal/g ^oC. So it takes 5 times more energy to heat 1 g of water than it takes to heat 1 g of sand. This is why, by midmorning on a warm sunny day, it is difficult to walk barefoot on beach sand—while the ocean, with its higher heat capacity, still feels relatively cool.

Safety

Wear safety gloves and safety glasses and take all necessary safety precautions while conducting both of these activities.

Money Laundering

Materials

• $1 Bill (or higher—donated by a student)
• Beaker, 250 mL
• Graduated Cylinder, 100 mL
• Denatured Ethyl Alcohol, 60 mL
• Water (tap is fine), 40 mL
• Crucible Tongs
• Match or Bunsen Burner

Procedure

1. Put on safety gloves and safety glasses.
2. Ask a student to “lend” you a dollar bill or one of higher denomination. (This demo is even more dramatic with a $5, $10, or $20 bill.)
3. Tell the class that money has germs, so you want to sterilize the bill.
4. Pour 40 mL of water into a 100-mL graduated cylinder.
5. Continue filling the cylinder with denatured ethyl alcohol to the 100-mL mark.
6. Pour the solution into the 250-mL beaker.
7. Submerge the bill completely in the solution, and tell the class that you are “money laundering.”
8. Remove the bill, unfold it, and tell the class you need to dry it quickly.
9. Hold a corner of the bill with crucible tongs while igniting the diagonally opposite corner with a burning match or Bunsen burner. Then remove the heat source.
10. Observe that the flames don’t consume the bill and also dissipate without aid. This should surprise the students.
11. Since the bill should be moist from the remaining water, pat it dry with a paper towel.
12. Have students “brainstorm” as to why the bill did not burn in the flames.
    Answer: The 40% water in the solution absorbed the heat and kept the bill from burning.

Boiling Water in a Paper Cup

Materials

• Paper Cup (non-waxed)
• Ring Stand (with iron ring and wire gauze)
• Bunsen Burner (with gas lighter)
• Water (tap is fine)

Procedure

1. Put on safety gloves and safety glasses.
2. Fill the paper cup a little over halfway with water.
3. Place the cup of water on the wire gauze and heat it with the Bunsen burner.
4. Watch the top of the cup burn down to the water level and stop.
5. Turn off the burner.
6. Have the students explain why the paper cup does not burn below the water level. Answer: Due to its high heat capacity, the water absorbed the heat and kept the cup from reaching its ignition temperature of 233^o C.

Note: Do not try this with a Styrofoam™ cup. Styrofoam™ is a good insulator and prevents the water from absorbing the heat.