These clear 250 mL Nalgene jars contain substances whose densities vary from 0.4-11.3 g/cm3. They can be passed around the classroom. 

Curriculum Notes 

This demo is usually used when the concept of density is being introduced. Presentation time varies.

One day of lead time is required for this project.

Discussion 

These substances can be presented as three pairs:

• white powders (polyvinyl alcohol and baking soda)
• clear liquids (grain alcohol and water)
• metals (aluminum and lead)

Technical data:

• polyvinyl alcohol, [-CH₂CHOH-]_n, MW = ~133,000
• grain alcohol (ethanol), CH₃CH₂OH, MW = 46
• water, H₂O, MW = 18
• baking soda (sodium bicarbonate), NaHCO₃, MW = 84
• aluminum, Al, AW = 27
• lead, Pb, AW = 207.2

Materials 

Six 250 mL Nalgene jars with the following labels:

• polyvinyl alcohol, 0.4 g/cm³
• grain alcohol, 0.79 g/cm³
• water, 1.0 g/cm³
• baking soda, 2.2 g/cm³
• aluminum, 2.7 g/cm³
• lead, 11.3 g/cm³

Procedure 

Jars may be passed around the classroom for students to examine. 

Safety Precautions 

None of these substances pose acute health hazards. Grain alcohol (ethanol) is a flammable liquid. A fire extinguisher should be available when presenting this demo. Lead can pose a chronic health hazard; any lead spills should be cleaned up thoroughly.