Viscosity: The Flow of Milk
Students exploring the viscosity of various fluids.Copyright 2012 Jennifer S. Haghpanah, Polytechnic Institute of NYU
Students study the physical properties of different fluids and investigate the relationship between the viscosities of liquid and how fast they flow through a confined area. Student groups conduct a brief experiment in which they quantify the flow rate to understand how it relates to a fluid's viscosity and ultimately chemical composition. They explore these properties in milk and cream, which are common fluids whose properties (and even taste!) differ based on fat content. They examine control samples and unknown samples, which they must identify based on how fast they flow. To identify the unknowns requires an understanding of the concept of viscosity. For example, heavy cream flows at a slower rate than skim milk. Ultimately, students gain an understanding of the concept of viscosity and its effect on flow rate.
Engineers commonly design equipment or devices that requires them to take into consideration the viscosity of particular fluids. Chemical engineers design chemicals of very different viscosities(ranging from rubber to petroleum to alcohols and aqueous solutions) and all their processes and reactions must take into account the flow rate of these substances. In the design of artificial heart valves and vascular stents, biomedical engineers must have an intimate knowledge of the flow rate and properties of blood when it flows through arteries and veins in order to design devices that function correctly. Mechanical engineers who design combustion engines consider the liquid flow rate of oils, petroleums and fuels under different conditions. Understanding the relationship between viscosity and flow rate are essential in any engineering process involving liquids!
After this activity, students should be able to:
- Explain the reasoning behind the varying flow rates of milks with various fat content.
- Describe the relationship between viscosity and flow rate, and extrapolate information from it.
- Explain the importance of viscosity consideration in scientific use and engineering applications.
- Collect and analyze data from an experimental set-up.
- Identify dependent and independent variables in an experiment.