Purpose
To illustrate the concept of density by making a density column that can be used to determine the relative densities of several solid objects.
Materials
- Syrup (brown) or light corn syrup
- Dishwashing detergent (green)
- Water (colored red with food coloring)
- Vegetable oil (yellow)
- Ethanol (colored blue with food coloring)
- 250 mL glass graduated cylinder
- Small ice cube
- Small
- Small piece of
- Read the MSDS/WHMIS sheet for ethanol
- Ethanol is highly volatile and flammable, ensure no open flames are present (candle, Bunsen burner)
- Avoid inhalation of ethanol vapors
Procedure
- Pour 50 mL of syrup in a 250 mL glass graduated cylinder and let the liquid settle.
- Tilt the graduated cylinder and pour in 50 mL of dishwashing detergent slowly down the side of the cylinder then let the liquid settle in the upright position. The detergent should form a layer on top of the syrup.
- Repeat step 2 for the other liquids: red colored water, vegetable oil, then blue colored alcohol.
- Drop in various items (ice, cork, chalk, …) and observe the level the object sinks or floats at.
- Cover the cylinder in plastic wrap and leave undisturbed for several days before re-examining.
- Shake the graduated cylinder and re-examine after several minutes.
Results
The colored liquids layer in the column (from bottom to top: brown, green, red, yellow, blue).
Follow-up Teaching Notes
The liquids, with the exception of the oil, are miscible so care must taken when layering them.
Connections
Density, separation methods, solubility, diffusion.
Extension
- Students could determine the densities of the liquids to generate order of pouring the liquids.
- The actual densities of the solids can be determined and compared to their position in the density column.
Disposal/Clean-up
Contents of the cylinder can be safely poured down the drain but ensure that solids are strained out or removed from the sink trap and placed in the garbage.
