Determining Concentration
Students use color sensors to measure the percent of light reflected from a solution.Copyright 2013 Jasmin Hume, Polytechnic Institute of NYU
Students quantify the percent of light reflected from solutions containing varying concentrations of red dye using LEGO© MINDSTORMS© EV3 bricks and color sensors. They begin by analyzing a set of standard solutions with known concentrations of food coloring, and plot data to graphically determine the relationship between percent reflected light and dye concentration. Then they identify dye concentrations for two unknown solution samples based on how much light they reflect. Students gain an understanding of light scattering applications and how to determine properties of unknown samples based on a set of standard samples.
Many types of engineers, such as chemical, biomedical and environmental engineers, often need to know information about solution properties (such as concentration) that is difficult to determine from visual observation alone. Regulating the concentration of various chemical compounds, whether soluble or insoluble, is important to chemical engineers working on large-scale production of medicines, food, oil and gas, and virtually every liquid you can think of. In another example, biosensors (designed by biomedical engineers) must be highly sensitive in order to produce accurate measurements of low biomolecule concentrations in biological fluids, such as blood and saliva. The technique of measuring concentration in a liquid using reflected light or light scattering is widespread in engineering industry applications, as it provides quick, convenient and fairly accurate concentration measurements in a process that can be automated with the help of robotics.
After this activity, students should be able to:
- Explain how light reflection can be used to measure the concentration of a solution.
- Draw an approximate linear regression through a given set of data.
- Calculate percent change and percent error.
- Use a set of standard solutions to determine information about the concentration of unknown solutions.