Lesson Plan

Surface Tension

Dropping water on a penny to see surface tension in action. This will take place over two one hour sessions.

Students will be able to identify that surface tension is the skin-like surface that holds water together.

Students will be able to state that surface tension gets stronger with salt and weaker with soap. 


ISTE standards: 

1a. Apply existing knowledge to generate new ideas, products, or processes. 

1c. Use models and simulations to explore complex systems and issues. 

2d. Contribute to project teams to produce original works or solve problems.

3d. Process data and report results.

4c. Collect and analyze data to identify solutions and/or make informed decisions. 


Grades 2 - 4
All Notes
Teacher Notes
Student Notes

1 Hook/ Attention Getter

Day 1: Introduce the topic by showing a video of water bugs "walking" on the surface of the water. Ask: How do you think that these water bugs stay on top of the water? Invite students to see task card #1 to answer this question in the preassessment. 

Student Instructions

See task card #1 to access the pre-assessment question 

2 Direct Instruction

Activity: Exploring

Introduce the idea of surface tension. Have students record the definition of surface tension in the glossary of their science notebooks: The skin-like surface that holds water together. Discuss this definition as a class. 

Student Instructions

Record the definition of surface tension in glossary. Engage in class discussion. 

3 Guided Practice

Activity: Exploring

Introduce the penny activity. Demonstrate for the class how to set up materials. Explain process of dropping one drop of water at a time very slowly. Make sure to count how many drops fit on the penny before the water spills over. After giving a demonstration, have students set up the same materials and repeat the process of dropping water on the pennies. Invite students to see task card #2 to record data. 

Student Instructions

Listen and watch attentively.  Once the teacher is finished with the demonstration of the experiment, work in pairs to complete the experiment. See task card #2 to record data while performing the experiment. One partner will carry out the experiment while one partner records. Partners will switch roles after five trials each. 

4 Independent Practice

Activity: Exploring

Walk throughout the classroom giving assistance as needed. Introduce repeated experiment with salty and soapy water, explaining that this is what we will be doing next class. 


Day 2: Have students start by repeating the experiment with salty water. Once students are finished experimenting with salty water, have them repeat the process with soapy water. Have students access task code #2 again to record their data. 

Student Instructions

Continue to carry out experiment. Use task card #2 to record data. Clean up materials when finished. 


Day 2:Repeat the experiment using soapy water and salt water. Use the link of task card #2  to record data about how many drops of each type of water were able to fit on the penny with each trial. 

5 Independent Practice continued

Activity: Drawing

Invite students to see task card #3 in order to draw their observations of the water on the penny. Have students discuss their observations as a table group. 

Student Instructions

See task card #3. Follow the link to draw observations of the water on pennies. Engage in discussion about observations as a table group. 

6 Wrap Up

Activity: Conversing

Record data of how many drops fit on the penny for each type of water for the whole class, having each group report their highest data. Hold a class discussion about results and observations. Discuss the difference in the data and observations for regular, soapy, and salty water.  Facilitate discussion with the end goal of having students understand that the dome that the water formed on the penny was an example of surface tension holding water together and that surface tension gets weaker when soap is added, and stronger when salt is added. 

Student Instructions

Participate in discussion, share ideas, data, and observations.


By the end of this discussion, students should be able to identify what surface tension is and how it is affected by soap and salt.