Hands-on Activity: Messin' with Mixtures
Contributed by: Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder

 SummaryIn this activity, students investigate the properties of a heterogeneous mixture, trail mix, as if it were a contaminated soil sample near a construction site. This activity shows students that heterogeneous mixtures can be separated by physical means, and that when separated, all the parts will equal the whole.
 Engineering Connection Relating science and/or math concept(s) to engineering Separation of mixtures based on physical means is something that engineers are involved with quite frequently. Environmental engineers may be concerned with separating oil from water in the case of an oil spill, and chemical engineers may work with separating gasoline from oil to use for fuel. Both of these examples deal with separation by physical means but engineers might also work with separation of mixtures or solutions through chemical means. Engineers also use separation of mixtures and solutions in designing water and air treatment processes, and new medicines.

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 Grade Level: 5 (5-7) Group Size: 2 Time Required: 30 minutes Activity Dependency :None Expendable Cost Per Group Keywords: My Rating: Avg Rating: Not Yet Rated.Teacher Experiences  |  Share your experience!

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Educational Standards :

• a. Find equivalent forms of commonly used fractions, decimals, and percents using models, drawings, and computational strategies (Grade 5) [2009] ...more
• a. Develop, communicate, and justify a procedure to separate simple mixtures based on physical properties (Grade 5) [2009] ...more
• b. Share evidence-based conclusions and an understanding of the impact on the weight/mass of a liquid or gas mixture before and after it is separated into parts (Grade 5) [2009] ...more
•   Common Core State Standards for Mathematics: Math
• c. Find a percent of a quantity as a rate per 100 (e.g., 30% of a quantity means 30/100 times the quantity); solve problems involving finding the whole, given a part and the percent. (Grade 6) [2010] ...more
•   International Technology and Engineering Educators Association: Technology
• E. Technologies can be used to repair damage caused by natural disasters and to break down waste from the use of various products and systems. (Grades 6 - 8) [2000] ...more
•   Next Generation Science Standards: Science
• Conduct an investigation to determine whether the mixing of two or more substances results in new substances. (Grade 5) [2013] ...more

After this activity, students should be able to:
• Discuss properties of mixtures and solutions.
• Discuss methods for separating mixtures and solutions into their original components.
• Describe several engineering applications for mixtures and solutions.

Each group needs:

• Small bag of trail mix
• M&M® candy or other small candy – 3 pieces per student
• Stop watch or other timepiece
• Calculator
• Two copies of the Soil Sleuths worksheet

For the class to share:

• A balance for measuring mass
• A few cans of mixed nuts, fruit cocktail, or other items that list percentages of amounts contained

Today we are going to talk about mixtures and solutions. A mixture is made up of two or more kinds of matter, but sometimes you can still see the different components, like sand and water. A solution is a special type of mixture where you cannot tell the difference between the components, and it cannot be separated easily.
What are some other differences between a mixture and solution? Well, mixtures retain their original properties, and solutions do not. In most cases, a solution has different properties than the two or more parts that went into making it. Also, solutions are the combination of a solute and a solvent. For example, in salt water, the salt is a solute and water is the solvent. Is it possible to separate the different substances in a solution? The answer is yes. In salt water, the two parts of the solution may be separated by evaporation. Other times it may be as easy as using a filter or a screen.
Who can think of another example of a mixture or solution? (Have students list answers such as, bubble mix, lemonade, milk, etc.) What is the difference between milk and Italian salad dressing? (Possible answers include: difference in color, the milk is the same throughout the whole bottle while the dressing separates after it sits for a bit.) Mixtures and solutions that are the same throughout (like milk, Kool-Aid®, etc) are called homogenous. Ones that are not consistent throughout (like Italian salad dressing, oil and water, etc.) are heterogeneous. Heterogeneous mixtures and solutions are normally much easier to separate. Filtering is an easy way to separate heterogeneous mixtures. Large rocks can easily be separated from small rocks and sand. It is much harder to separate the individual parts of Kool-Aid® (water, sugar, Kool-Aid® packet mixture).
Why would an engineer care about mixtures and solutions? Well, engineers design ways to help separate mixtures and solutions in industrial, commercial and environmental processes. Can you think of any engineers that have worked with the mixtures or solutions we listed a minute ago? Chemical engineers work with the foods we encounter every day. They need to know what chemicals are safe to mix with foods when designing fertilizers and preservatives to keep food healthy for us to eat. Another example is environmental engineers working with acid mine drainage. Acid mine drainage is when metals from mining sites break down into the surrounding ground water and surface waters. This water from the mining area can become acidic and discolored, and disrupt the surrounding stream ecosystems. These areas can also be a health concern to humans who use the same groundwater resources. Engineers work on cleaning up the mixtures and solutions of metals and bacteria in acid mine drainage areas as well as streams, drinking water, air and soils. Engineers use knowledge of mixtures and solutions to help create environmental policies, and design water treatment processes, ways to help the environment, and new medicines to help people.
In this activity, we are going to look at a heterogeneous mixture as if it were a contaminated soil sample to be cleaned up by environmental engineers. We will separate the mixture by filtration and then create a solution using M&M® candies. Are you ready?

 Heterogeneous: Composed of multiple parts with different properties and not uniform throughout. Homogeneous: A mixture or solution that is uniform throughout.

Before the Activity

Prepare the materials and copy the Soil Sleuths worksheet.

With the Students

1. Have students define what a mixture and a solution is.
2. Give each group a small bag of trail mix. Explain to the students that this is a small sample of soil that was found outside of a construction site. Most soils are made up of many different small components. Some of the components in this soil sample are contaminants (dust, lead, paint). Soil contaminants can have high health risks when we come in direct contact with the soil or when the contaminants break down into the surrounding ground water and into our water resources. As environmental engineers, they need to determine the percent of each material found in the soil sample. This will help them decide how to clean up the contaminated soil.
3. Have the students observe their trail mix and ask them to classify it as a mixture or a solution.
4. Once they have determined that the bag is a mixture, have the students find the mass of each item/part. For this step, the students need to weigh everything. This includes little pieces of cereal or the "skins" from the peanuts.
5. Using the Soil Sleuths Worksheet as a guide, have the student groups compute the percentage of each part of the trail mix (i.e., What percent of the trail mix is peanuts?) Explain that this is one way engineers may measure the amounts of materials in something like a soil sample, in order to determine what materials are present and what form of clean up is needed. The teacher may need to help explain how to compute percentages depending on students' math level.
6. Have students round their percentages to the nearest hundredth. Compare this process of rounding money – dollars and cents. The final percentage should be close to 100%.
7. Have the students analyze their soil samples. For example, if peanuts and raisins are normal components of soil, such as minerals and organic matter, then how many contaminants (other parts of the trail mix), such as lead, dust and paint, were found in the sample? What percentage of the soil was contaminated? (Have the students add the percentages of the "other parts.") Was their sample pretty contaminated or not? What situations would a contaminated soil sample be of concern to engineers? (Possible answers: where animals graze, where people are building homes, parks, schools, playgrounds, drinking water, etc.)
8. Discuss other everyday products that provide information about percentages, such as canned juices and cocktail nuts. If possible, bring in a few of these items to show the students.
9. Finally, let the students enjoy the snacks as they discuss how a mixture is different from a solution. (When they are finished with Part 1, the teacher may let the students eat the trail mix, if desired.)

Be sure to have the trail mix in bags and the worksheets copied. Go over the directions and worksheet before the students attempt this activity. Be sure to give instructions before you pass out the candy.

Pre-Activity Assessment

Discussion Questions: Solicit, integrate and summarize student responses.
• What is one difference between a solution and a mixture? (Possible answers: Mixtures retain their original properties, solutions do not. Solutions cannot be separated by filters.)

Activity Embedded Assessment

Worksheet: Have the students complete the Messin' Around Worksheet; review their answers to gauge their mastery of the subject.

Post-Activity Assessment

Engineering Application: Have the students write a "report" for the construction company that was working the site where the contaminated soil was found. They should include in their report: if the soil was highly contaminated, what percent of contaminants was found in the soil, why these contaminants should be removed, and a recommendation for how their engineering firm might remove the contaminants from the soil for the construction company. (The last part is creative writing, since only filtering was focused on in the activity.)
Graph it! As an extra math extension, have students create a pie chart of their percentages from Part 1.

Have the students discuss how they could turn the trail mix bag into a solution. Allow student to write down their steps for completing this task and share their ideas with the class.
Have students research types of soil, water or air contamination. Have them report back to the class on what engineering processes have been developed for cleaning up these types of contamination, including bioremediation and electromechanical processes.
Have the students complete the oil spill activity in TeachEngineering.com. This activity has students create a model oil spill and discuss strategies for separating the oil from the water, a heterogeneous mixture.

For lower grades, do not use the Soil Sleuths Worksheet, only use observation techniques. Have the students make a list of things they learned, including differences and similarities of mixtures and solutions.

Trimpe, Tracy. Science Spot, Chemistry Lesson Plans, September 4, 2006, accessed September 7, 2006. http://www.sciencespot.net/Pages/classchem.html#Anchormixtures

Contributors

Brian Kay, Daria Kotys-Schwartz, Malinda Schaefer Zarske, Janet Yowell