In-class teacher demonstration

For the teacher:

• 1 standard size paper plate
• 25 mL water
• less than 2 g of ground black pepper
• 5-10 drops of liquid dish soap (Dawn or similar)

For the class to share

• laptop or computer with projector (to display Exploring Surfactants Presentation to class)

Part 1: Investigating surface tension and surfactants

Note: To test the surface pressures of different chemicals, each group will need to assemble a testing apparatus. This activity provides two options: Method 1 is a low-cost DIY version that will collect more general qualitative data, while Method 2 uses a scientific triple-beam balance (which may be available in some classrooms) to collect more precise quantitative data.

Method 1: Building a low-cost DIY surface tension balance

Each group needs:

• 3 18 oz. plastic cups
• 1 small weigh boat
• 1 spool of thread
• 1 sewing needle
• 2 small wooden dowels or chopsticks
• 1 pair of scissors
• 1 utility knife
• 1 permanent marker
• 1 ruler with units in centimeters
• modeling clay
• tape
• water, preferably distilled
• 2 g SLSA powder
• weigh boat
• spoon or stirring rod
• 100 mL graduated cylinder
• 1 ml bulb pipette
• permanent marker
• paper towels
• (optional) 1 electronic balance

For the entire class to share:

• 1 electronic balance

Method 2: Assembling a scientific beam balance apparatus

Each group needs:

• 1 50 mL beaker
• 1 spool of thread
• 1 medium plastic button (preferably flat-faced, 4 holes, approximately 17-20 mm in diameter)
• 1 ruler with units in centimeters
• (optional) 1 triple-beam pan balance (e.g., Ohaus Cent-O-Gram™ Balance or similar)

For the class to share

• 1 triple-beam pan balance (e.g., Ohaus Cent-O-Gram™ Balance or similar)

Part 2: Investigating protein aggregation solutions

Each group needs:

• 50 mL of four mystery solutions (labeled A, B, C, D) for testing. Each solution should be prepared at a 4% concentration using one of the following compounds: a surfactant (such as SLSA powder), a stabilizer (such as sugar), or potentially disruptive agents (such as borax or salt).
• 1 hand mixer with 2 eggbeater attachments
• 100 mL egg whites
• 5 small containers with transparent lids
• 1 bowl large enough to mix solutions in
• 5-10 pipettes
• 50 mL water, preferably distilled