• Site Information
• Lesson Plans
• Teaching Resources
• Class Activities
• Financial Literacy

• Teacher's Guide Quick guide to this
  site's resources

• Teacher's Network
  Get all the news on
  the latest education
  resources from the
  United States Mint
  right in your in-box!
  Sign up Today!

How Many Drops?

Main Subject Area: Science

Additional Subjects: Mathematics

Duration of Lesson:  90 minutes

Keywords:

• Surface Tension

Brief Description:

Students will explore surface tension and the effect that tensioactive substances (soap) will have on it, through the use of coins. They will also collect data on coins and their different properties.

National Standard(s):

• Science as inquiry
• Physical science

Additional Subject Area Standard(s):

• Data Analysis and Probability
• Problem Solving

Objectives:

Students will explore surface tension and the effect that tensioactive substances (soap) will have on it, through the use of coins.

Students will collect data on coins and their different properties.

Materials (online):

Materials (offline):

For each group of 4 students you will need:

1 penny, 1 nickel and 1 quarter

Graphing paper

Eye dropper

Bottle of water

Soap (glycerine or dish soap)

Paper towels

Coins Used in Lesson:

Circulating pennies, nickels and quarters

Grade Level(s):   6-8  

Procedures (online):

Procedures (offline):

1. Brainstorm with your students about their knowledge of the composition of coins.

2. Discuss the concept of surface tension as a class.

3. Ask your students to estimate and record how many drops of plain water they think will fit on each of the coins. Have them estimate for each side (obverse and reverse.) Then have the students record their estimates for the number of drops each side of each coin will hold of soapy water.

4. Have your students clean each of the coins and make sure there is no remaining soap.

5. Have your students test their hypotheses by dropping first the plain water on each side of each coin and then the soapy water. They should record their results next to their predictions.

6. Each group of 4 can make a chart of their results. Stem and leaf plots of their predictions and actual results help the students to see their data. Students can then analyze the data for the mean, median, mode, and average.

7. Students should then draw and write conclusions based on their data.

Assessment / Evaluation:

Students’ notes and graphs can be used for assessment.

Differentiated Learning Options:

As an extension students can add 15 drops of plain water to a penny. Then add 3 drops of soapy or salty water and see what happens.