Purpose

To demonstrate surface effects.

Materials

1-L Beaker or shallow glass pie pan

1 g Flowers of sulfur (fine sulfur powder)

1 mL Dishwashing detergent in beaker

Tap water

Petri dish

25 mL Homogenized fresh whole milk (4% milk)

Food coloring

Thin-stem transfer pipet

Triple-beam balance

Support stand with ring

Wire circle with wire loop (60 cm heavy gauge aluminum wire; solder; soldering iron; suitable soldering work surface)

Safety and Disposal

There are no unusual hazards in this experiment. No special precautions are required in this experiment; follow routine laboratory precautions. The materials used in this activity may be disposed of safely at the sink.

Procedure

1. Place 500 mL tap water in a 1-L beaker. Sprinkle some powdered sulfur on the surface of the water. Dip your clean dry finger into the water, and note the effect on the sulfur.

2. Dip your finger into some liquid dish detergent, and then dip it into the beaker containing the sulfur. Note the effect on the sulfur.

3. Fill a Petri dish bottom half-full of whole milk. Drop some food coloring onto the surface. Fill a transfer pipet with some liquid dishwashing detergent. Place a few drops of the detergent on the inside wall of the Petri dish above the level of the milk. Note any evidence for reaction. After a long period of time, the apparent changes cease.