Penny Perfect Properties (Solid-Liquid Interactions)
Students investigate the property dependence between liquid and solid interfaces and determine observable differences in how liquids react to different solid surfaces. They compare copper pennies and plastic "coins" as the two test surfaces. Using an eye dropper to deliver various fluids onto the surfaces, students determine the volume and mass of a liquid that can sit on the surface. They use rulers, scales, equations of volume and area, and other methods of approximation and observation, to make their own graphical interpretations of trends. They apply what they learned to design two super-surfaces (from provided surface treatment materials) that are capable of holding the most liquid by volume and by mass. Cost of materials is a parameter in their design decisions.
Demonstration of how a liquid and solid can interact allowing for the liquid to "stack" on the solid surface without spilling over the edges.Copyright 2009 Courtney Herring, Washington State University
In the field of heat transfer; mechanical, chemical and electrical engineers all work to increase the amount of heat that can be removed from surfaces. Maintaining a certain temperature on a surface is critical, especially in preventing circuit burnout in electronics such as computers, satellites and lasers. In many cases, engineers enhance heat transfer by coating surfaces with liquids. In those cases, the amount of liquid used and the nature of the liquid-solid interface are critical for successful designs. For example, too little contact between a liquid and solid can decrease, instead of increase, the heat removal. Engineers contribute their individual specializations to design challenges. If the goal is to improve heat transfer rates in electrical systems, a mechanical engineer may study the heat transfer through a heated surface using temperature measurements so as to be able to provide improvements to the design (construction). A chemical engineer may understand how materials properties affect the heat transfer through a heated surface and be able to provide improvements to the materials. And an electrical engineer may understand the effect that changing the heat transfer material has on the performance or efficiency of the electronics.
After this activity, students should be able to:
- Follow procedures to collect data while changing more than one variable.
- Represent measured data graphically and be able to explain in their own words what the graphical data means.
- Provide supported reasoning for final design recommendations using engineering concepts, such as surface tension is a changing property (soapy, salty, pure water), solid-liquid interface (smooth vs. rough).
Goals:
- Math competency: Skills and appreciation for data collection and analysis used in real life.
- Quantitative literacy: Ability to follow procedures and provide recommendations.
- Engineering applications: Engineering design process, material selection and cost considerations.
- Cultural relevancy: Follow procedures, collaborative work in small groups and hands-on activities.