Hands-on Activity Wet Pennies

Learning Objectives

After this activity, students should be able to:

• Give an example of a hypothesis that is based on an observation of a natural phenomenon.
• Give an example of an experiment designed to address a specific hypothesis.

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

• 3 small beakers (50-100 ml) or plastic cups (about 4 to 8 ounces) per group
• 1 disposable pipette per student, plus a few extras
• 1 penny per student
• rubbing (isopropyl) alcohol, two 16-ounce bottles
• vegetable oil, one 32-ounce bottle
• paper towels, several per student
• water

Worksheets and Attachments

Pre-Req Knowledge

Students should be able to calculate the average of four numbers less than 50.

Introduction/Motivation

This activity engages students' attention very quickly and thus requires little or no introduction. Simply divide the class into teams of four students each, provide the materials and written instructions for students, and let them proceed with the activity.

Procedure

Before the Activity

• Gather materials and make copies of the Wet Pennies Handout.
• As indicated in the student instructions, each team needs three containers (beakers or cups) of liquid: one containing water, one containing rubbing alcohol, and one containing vegetable oil. For each liquid, use about 2 ounces (about one-half inch of liquid height). Label the containers.

With the Students

1. Divide the class into groups of four students each.
2. Pass out the materials and handouts. Emphasize the need to follow the instructions carefully, especially in regard to the order of the liquids they test on their pennies.
3. After the experiment is done, lead a concluding class discussion, as described in the handout and Assessment section. Ask the Investigating Questions.

Vocabulary/Definitions

hypothesis: A tentative explanation for a fact or set of observations, which can be tested objectively.

Assessment

Concluding Discussion: As outlined in the Wet Pennies Handout, lead a class discussion so students can share and compare results and conclusions. Ask the Investigating Questions. Listen to students' discussion contributions and answers to gauge their level of comprehension.

Investigating Questions

• How many drops of water fit on your penny? Was this number similar to the number other members of your group got? What do you think could cause differences between the numbers you got? (Students might respond that individuals have different dropping styles [speed, height they hold the pipette above the coin, etc.] and that newer pennies seem to have a more distinct rim, which could allow more water to stay on the penny. They might also speculate that differences between the pipettes could cause different sized drops to form.)
• Did you get different averages for the three liquids? If so, which liquid allowed you to put more drops on the penny?
• Are your results consistent with those of other groups? In what ways are they the same or different?

Troubleshooting Tips

Some students may get the mistaken idea that the water-dropping activity is some sort of contest that they can win by getting the most drops, of any liquid, on the penny. Try to avoid giving students this idea, and if they come up with it on their own, explain that the point is for them to be able to fairly and accurately compare the numbers of drops of each liquid a penny can hold -- not to compare how many drops each student can get a penny to hold. To fairly and accurately compare the number of drops of each liquid a penny can hold, students need only try to use the same dropping technique (same squeezing pressure on the pipette bulb, same height it is held above the penny) for each liquid.

Activity Extensions

Students may want to immediately test the hypotheses they develop as part of this activity. If time allows, some of the ideas they are likely to generate can be quickly and easily tested, and it is a good idea to encourage their enthusiasm by letting them do so. See the Lesson Closure and Lesson Extension Activities sections of the How Many Drops? associated lesson or more information.

Copyright

Contributors

Supporting Program

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.

This activity was originally published, in slightly modified form, by Duke University's Center for Inquiry Based Learning (CIBL). Please visit http://ciblearning.org/ for information about CIBL and other resources for K-12 science and math teachers.