Concentrate This! Sugar or Salt...
Students investigate the property dependence between concentrations and boiling point. In section 1, students first investigate the boiling point of various liquid solutions. In section 2, they analyze data collected by the entire class to generate two boiling point curves, one for salt solutions and one for sugar solutions. Finally, in section 3, students use the data they have analyzed to determine how to create a solution that has a particular boiling point and is a cost-effective design.
A beaker on a hotplate.Copyright 2010 Courtney Herring, Washington State University
In the field of chemical engineering, it is important to understand the dependency of concentration on the physical properties of a liquid. Small changes (intentional and unintentional) in the composition of a liquid mixture can make dramatic changes to the liquid's boiling, melting or freezing point, density, viscosity or surface tension. Chemical engineers must understand how these changes can impact the function of a substance so they can account for, and design, new substances. For example, small changes can make the difference between your car starting in the winter or not, depending on whether or not the correct chemical composition of anti-freeze or motor oil was used.
After this activity, students should be able to:
- Follow step by step procedures to conduct an experiment.
- Apply the concept of concentration changes to alter boiling point.
- Correctly use units of concentration.
- Calculate solute mass from a known concentration and solvent mass.
- Determine when boiling occurs and measure a liquid's boiling point.
- Apply the understanding of boiling points and altering boiling points to a real-life engineering situation.
GOALS:
- Math competency: Skills and appreciation for data collection 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: How to follow procedures, collaborative work in small groups and hands-on activities.