Simply put, viscosity is the measure of a fluid’s thickness or its resistance to deformation or change. Fluids can either be liquid or gas. A type of force called stress can cause viscosity, which is the outcome of friction among fluid molecules moving around at various speeds.
What you need:
• A tall graduated cylinder
• Hand sanitizer
• Liquid glue
• Cooking oil
What to do:
- Test the sample liquids one at a time. Fill your graduated cylinder with a liquid. Make sure to leave about two centimeters of space at the top to prevent overflow. Each time you fill the cylinder with liquid, do so to the same height.
- Take the marble and hold it at the mouth of the cylinder. Prepare your stopwatch with your free hand. Start the timer once you let go of the marble and let it drop into the liquid. Stop the timer when the marble reaches the bottom.
- Document the height of the liquid, the type of liquid, and the length of time (in seconds) the marble traveled from the top to the bottom of the cylinder.
- After repeating these steps on all the sample liquids, calculate the average time:
Average time = (1st time + 2nd time + 3rd time) / 3
- Calculate the marble’s average velocity as well:
Velocity = distance (height of your liquid) / time (average time)
From least to greatest viscosity, the liquids are: water, cooking oil, syrup, glycerin, hand sanitizer, honey, and liquid glue. (*** Note that the viscosity of the liquids depends on the brand.)
The friction that occurred between the fluid molecules counters fluid deformation and change. The marble’s weight (gravitational force) also stresses the liquid sample. The best samples that resist these changes are the high viscosity ones like liquid glue and honey.
Viscosity is usually temperature-sensitive. Gases and liquids become thinner or less-viscous when they are heated.
You can try this experiment on other sample liquids such as peanut butter, ketchup, blood, and chocolate syrup.