CH151 Viscosity Racetrack Teacher Kit
Jacob Laser
Description: Students will observe the physical properties of several liquids in order to make an educated guess as to which liquid will dribble down a uniform ramp the fastest.
Learning goal: Students will understand some of the array of physical properties that can be present in a liquid. They will begin look for correlations between different physical properties.
Recommended grades: 2-7
Key concepts
Viscosity = How much a substance resists flowing. Also known as thickness
Surface tension = The skin formed on the surface of a fluid caused by intermolecular attraction of the surface molecule to the rest of the liquid.
Materials (20 students):
Water + blue food coloring
Green soap
Isopropyl alcohol + red and blue food coloring
Liquid starch
Vegetable oil
5 cuvettes
1 balance
1X50ml graduated cylinder
5 capillary tubes
1 box of 500 Eye droppers
50 small uniform buttons with a diameter of less than 15 mm
5 small weigh boats
5 ½” by ½” squares of aluminum foil
10 sheets of corrugated plastic w/ 5 grooves about 4” long
10 large weigh dishes
Procedure
Draw this table on the board and fill with data as it is determined.
water / isopropanol / oil / soap / starchdensity
capilary height
mixes with water (yes/no)
surface tension (buttons)
average place in race
Students will determine the density of each liquid
· Measure the volume of a cuvette
· Zero out a scale with the cuvette on it
· Fill one cuvette with each liquid and mass each
· Determine the densities of each liquid
Students will test capillary action of each chemical
· One student will measure for each chemical
· Place finger over one end of capillary tube
· Place capillary tube down to bottom of liquid inside cuvette
· Release finger and count to 20
· Measure how high the liquid column extends over the edge of the cuvette
Students will test if the substances mix with water
· Put a drop of each liquid in its own cup of water
Students will test relative surface tensions of the liquids
· Add small buttons to a sheet of aluminum on the surface of the liquid to see how much weight is needed to break the surface tension (for more advanced students you can have them calculate the exact amount of pressure needed to break the surface tension in Pascals)
Students will place one drop (up to the second small area of the pipette before the main section) of each chemical into the edge of the corrugated plastic.
· Tilt the plastic and see which is fastest.
· Average the results of the class to determine fastest liquid