Hands-on Activity Concentrate This!
Sugar or Salt...

Learning Objectives

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.

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

NGSS: Next Generation Science Standards - Science

Common Core State Standards - Math

International Technology and Engineering Educators Association - Technology

State Standards

Materials List

Section 1- Boiling Point Data

Each group needs:

• beaker tongs or hot gloves
• calculator
• 300 ml beaker
• thermometer
• burner or hotplate
• 200 ml water
• Section 1 Worksheet
• graduated cylinder
• glass stir rod
• aluminum foil (4" x 4" piece) used to form a lid over beaker during boiling

To share with the entire class:

• electronic balance (capable of weighing 200 ml water plus beaker weight)
• salt, approximately 250 g for every other group (each group only tests one solute)
• sugar, approximately 540 g for every other group (each group only tests one solute)

Section 2 - Data Analysis

Each group needs:

• Section 2 Worksheet
• calculator
• ruler

Section 3 - Design

Each group needs:

• beaker tongs or hot gloves
• calculator
• 300 ml beaker
• thermometer
• burner or hotplate
• 200 ml water
• Section 3 Worksheet
• graduated cylinder
• glass stir rod
• aluminum foil (4" x 4" piece) used to form a lid over beaker during boiling

To share with the entire class:

• electronic balance (capable of weighing 200 ml water plus beaker weight)
• salt, approximately 100 g per group
• sugar, approximately 180 g per group

Worksheets and Attachments

Pre-Req Knowledge

Students should be familiar with:

• Math concepts: line graphs and fractions.
• Science concepts: concentration, mass, weighing practices, boiling point.

However, this activity could be used as a means of introducing some or all these concepts.

Introduction/Motivation

(The motivation for this activity is to familiarize students with concentrations by providing opportunities for them to first create solutions and calculate the concentration based on solute mass, test solutions for boiling point, then predict performance of other concentration based on data analysis, and then finally to calculate solute mass based on the needed concentration, and verify their prediction through testing boiling point of the new solution. Students also will understand the importance of determining the cost of a solution and relate this cost analysis to the engineering design process; engineers must optimize cost of materials in designs.)

How do chemical engineers design new materials and products in the lab? The method of test, analyze and validation is common practice in engineering. Today you will be doing the same thing. This gives you the opportunity to explore and understand data analysis in true lab situations where you must try to control as many variables as possible to produce the most accurate results.

What is the connection between chemistry and chemical engineering? (Listen to student ideas.) Chemical engineering is the application of a person's knowledge of chemicals, mixtures and solutions to solve real-world problems. What might be some examples? (Listen to student ideas.) There are so many examples. One example is that chemical engineers design specific anti-freeze and motor oil chemical solutions to help your car work more efficiently and effectively in specific conditions.

Procedure

Before the Activity

• Gather materials.
• Make copies of Section 1 Worksheet, Section 2 Worksheet and Section 3 Worksheet.
• Test the salt and sugar concentrations to confirm the boiling point curves. Be sure to include the boiling point of the pure water sample.

With the Students

Before start of the lab:

Introduction to Solutions

1. Discuss what makes a solution: a solvent plus a solute.
2. Give examples of solutions and have students come up with their own examples (use Worksheet 1 to help guide this).
3. Describe concentration as a means of describing (defining) a solution. Concentration is a measure of how much of some substance is contained in a mixture.

• Introduce units and decide which ones will be used in the labs.
• Introduce equation to calculate concentration based on masses of solute and solvent (use Worksheet 1 to help guide this).

4. Discuss why concentration might be an important property of a mixture and how concentration may change other known properties (density, viscosity, surface tension, boiling point, freezing point). Specifically, use this information to introduce the concept of chemical engineering.

• Salt water fish tanks.
• Saline solutions used in hospitals.
• Why salt is put down on roads in the winter or why we make homemade ice cream by spreading salt on the ice. This is an example of engineering the defined environment- applying what engineers know about melting points and solutions to fix a real-world problem.

5. Discuss how to use lab equipment.

• Review how to use and read a thermometer.
• Review how to use a balance and tare weights if necessary (ensure they are familiar with grams as opposed to ounces which sometimes appear on electronic balances).

6. Introduce the definition of chemical engineering and describe real-life problems that chemical engineers might try to solve. Refer to the Introduction and Motivation section as an example.

Day 1: Section 1

1. Hand out Section 1 Worksheet.
2. Introduce the activity, engineering connection, and strategy for the four-day lab:

Day 1: Section 1 Worksheet (definitions and determining boiling point of various solutions).

Day 2: Section 2 Worksheet (data analysis and determining the best line of fit on a graph for various concentrations of salt and sugar).

Day 3 and 4: Section 3 Worksheet (design and test a solution to have a specific boiling point based on previous calculations; connect this "design criteria" to what engineers must do, that is, meet specifications).

3. Discuss results (if time at the end of class, once everyone is done).

Day 2: Section 2

1. Hand out Section 2 Worksheet.
2. Discuss results (if time at the end of class, once everyone is done).

Day 3: Section 3

1. Hand out Section 3 Worksheet.
2. Discuss how students can calculate the solute mass necessary to achieve the required boiling point.
3. Have students design their solutions and begin conducting the tests.

Day 4: Section 3 (continued)

4. Report results and check solutions.

Vocabulary/Definitions

boiling point: The point at which one can see a steady/continuous/rapid boiling of a liquid. This point is also characterized by a constant temperature, as long as the concentration is not being changed.

concentration: A measure of how much of some substance is contained in a mixture.

solute: The material being dissolved in a solution, typically the material present in a lesser mass, and the material that is changing state. In this activity example, the salt and sugar are the solutes.

solution: A mixture of two or more substances. In this activity, salt water solution or sugar water solution.

solvent: The liquid substance able to dissolve other substances. In this activity, water is the solvent. The solvent does not change its state when forming a solution.

Assessment

At activity end, review and grade completed student worksheets to gauge their mastery of the concepts.

Safety Issues

• Students should not drink any chemicals even those labeled water or soda because contamination is always possible.
• Students should always use safe lab practices especially when working with heat. Use tongs when handling hot containers and wear lab goggles to protect eyes.

Troubleshooting Tips

Be sure to test the boiling point of the water that will be used. A deviation of a few degrees in boiling point may exist, depending on elevation and water supply.

Ensure that the thermometers being used are accurate and precise enough to capture half-degree changes in temperature. One option is to use digital thermometers. Also, ensure that the thermometer range covers the range of boiling points possible with the solutions (~212 °F to 240 °F).

During boiling, if water vapor (steam) is escaping from the beakers, it means the concentration inside the beaker is increasing due to a loss in solvent mass. To ensure the least error, encourage students to keep beakers completely covered. If possible, use rubber bands to secure the foil lids on the beakers.

Activity Extensions

To reinforce students' understanding of concentration, provide them with two or three unknown solutions for which they must determine the concentrations. Then, as an added challenge, challenge students to develop a method to determine if the unknown is a salt or sugar solution. This would be based on the mass of the solution as long as they are given the mass of the solvent.

Ask students to create concentration curves based on other measurable properties such as density. They could then compare to see if one measurement is a better predictor for determining an unknown.

Have students perform cost analysis of their solutions for section 3, comparing their group results to other group results.

Activity Scaling

• For lower grades, minimize testing to only one solute (salt) then have students collect data as a class. During section 3, have students calculate the cost to create the required boiling point solution.
• For upper grades, have students determine the effect each solute has on the boiling point error. For example, for a one-degree boiling point increase, it requires more sugar than salt. Therefore, the same precision of weighing results in a lower error associated with the sugar solution than the salt solution. Have students come up with methods to minimize these measurement errors. In addition, have students come up with an equation to determine the boiling point of a solution containing water + salt + sugar.

Copyright

Contributors

Supporting Program

Acknowledgements

This content was developed by the Culturally Relevant Engineering Application in Mathematics (CREAM) Program in the Engineering Education Research Center, College of Engineering and Architecture at Washington State University under National Science Foundation GK-12 grant no. DGE 0538652. However, these contents do not necessarily represent the policies of the NSF, and you should not assume endorsement by the federal government.