# UnitStudents as Scientists

### Summary

Through two lessons and their associated activities, students do the work of scientists by designing their own experiments to answer questions they generate. Through a simple activity involving surface tension, students learn what a hypothesis is—and isn't—and why generating a hypothesis is an important aspect of the scientific method. In the second activity, with bubble gum to capture their interest, students learn to design and conduct controlled experiments to answer their own questions about the amounts of sugar (or artificial sweetener) in bubble or chewing gum.

### Engineering Connection

Designing experiments to test hypotheses is an act of engineering creativity. Scientists practice engineering whenever they design new experiments to test hypotheses. In addition chemical engineers spend time in laboratories creating products that have never existed before, everything from adhesives to cleaners to shampoos and fertilizers.

### Unit Overview

In the first lesson and its associated activity, students conduct a simple test to determine how many drops of each of three liquids can be placed on a penny before spilling over. Because of the different surface tensions of the three liquids—water, rubbing alcohol and vegetable oil—more water can be piled on top of a penny than either of the other two liquids. However, this is not the main point of the activity. Instead, students are asked to come up with an explanation for their observations about the different amounts of liquids a penny can hold. In other words, they are asked to make hypotheses that explain their observations, and because middle school students are not likely to have prior knowledge of the property of surface tension, their hypotheses are not likely to include this idea. Then, they are asked to come up with ways to test their hypotheses, although they do not need to conduct these tests. The important points for students to realize are that 1) the tests they devise must fit their hypotheses, and 2) the hypotheses they come up with must be testable in order to be useful.

In the second lesson, students chew bubble gum until it loses its sweetness, and after allowing the chewed gum to dry for several days, they determine the amount of mass lost. From the mass lost, they calculate the percentage of sugar that was in the gum originally. This teacher-led activity causes students to generate new questions about the varieties of chewing gums and their ingredients, and it also points out the need for controls. Students then design and execute new, controlled experiments based on their own questions. When students ask their own questions and devise ways to answer them scientifically, they begin to truly understand and appreciate the scientific method.

### 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.

See individual lessons and activities for standards alignment.

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### More Curriculum Like This

Middle School Lesson
How Much Sugar Is in Bubble Gum?

After a piece of gum loses its sweetness, it can be left to dry at room temperature and then the difference between its initial (unchewed) mass and its chewed mass can be used to calculate the percentage of sugar in the gum. This demonstration experiment is used to generate new questions about gums ...

Middle School Activity
Does Your Chewing Gum Lose Its Sweetness?

Student chew a piece of gum until it loses its sweetness, and then leaves the gum to dry for several days before weighing it to determine the amount of mass lost. students work in groups to design and conduct new experiments based on questions of their own choosing.

Middle School Lesson
How Many Drops?

In this lesson and its associated activity, students conduct a simple test to determine how many drops of each of three liquids can be placed on a penny before spilling over. The three liquids are water, rubbing alcohol, and vegetable oil; because of their different surface tensions, more water can ...

Middle School Activity
Wet Pennies

Students conduct a simple test to determine how many drops of each of three liquids—water, rubbing alcohol, vegetable oil—can be placed on a penny before spilling over. Because of their different surface tensions, more water can be piled on top of a penny than either of the other two liquids. Howeve...

### Assessment

After completion of this unit, expect students to be able to:

• Describe a simple experiment and state a hypothesis that could be tested by the experiment. An example of such an experiment could be that a student tested the effects of adding fertilizer to the soil of a bean plant grown in a flowerpot. (A suitable hypothesis might be: "Adding fertilizer causes the plant to grow taller than it would without the addition of fertilizer.) Then students describe a test of the hypothesis. (For example: Growing two plants under identical conditions, one with fertilizer added and one without.)
• As a written assignment, explain why a control should have been used in the initial gum experiment.
• As a written assignment, describe an experiment to determine whether sugarless gum loses as much mass after chewing as regular gum.

### Contributors

Mary R. Hebrank, project writer and consultant, Duke University

### Supporting Program

Engineering K-Ph.D. Program, Pratt School of Engineering, Duke University

### Acknowledgements

This content was developed by the MUSIC (Math Understanding through Science Integrated with Curriculum) Program in the Pratt School of Engineering at Duke University under National Science Foundation GK-12 grant no. DGE 0338262. However, these contents do not necessarily represent the policies of the NSF, and you should not assume endorsement by the federal government.