In 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.
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- Colorado: Math
- Use proportional relationships to solve multistep ratio and percent problems. (Grade 7)  ...show
- Colorado: Science
- a. Develop, communicate, and justify a procedure to separate simple mixtures based on physical properties (Grade 5)  ...show
- 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)  ...show
- 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)  ...show
- 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)  ...show
- Next Generation Science Standards: Science
- Conduct an investigation to determine whether the mixing of two or more substances results in new substances. (Grade 5)  ...show
- 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
- 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
|Composed of multiple parts with different properties and not uniform throughout.|
|A mixture or solution that is uniform throughout.|
Before the Activity
With the Students
- Have students define what a mixture and a solution is.
- 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.
- Have the students observe their trail mix and ask them to classify it as a mixture or a solution.
- 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.
- 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.
- 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%.
- 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.)
- 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.
- 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.)
- 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
Trimpe, Tracy. Science Spot, Chemistry Lesson Plans, September 4, 2006, accessed September 7, 2006. http://www.sciencespot.net/Pages/classchem.html#Anchormixtures
Brian Kay, Daria Kotys-Schwartz, Malinda Schaefer Zarske, Janet Yowell
© 2006 by Regents of the University of Colorado
Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
Last modified: February 11, 2016