1. Penny Lab: Exploring the Scientific Method
6th Grade
Penny Lab: Exploring the Scientific Method

2. Penny Lab We are going to explore:
Examination of changes in surface tension of a liquid between water and water with soap added
The effects of soap on the surface tension of water
How soap affects the cohesion of water molecules and the number of drops of water that can fit on a penny

3. Penny Lab
Brainstorm…
What do I know about water molecules and soap?

4. Penny Lab
Title
Laboratory Report:
_Drops on a Penny_

5. Penny Lab Research the following terms: Surface Tension Cohesion
Surface Tension: the force that causes the molecules on the surface of a liquid to be pushed together and form a layer
Cohesion: molecular attraction by which the particles of a body are united throughout the mass

6. Penny Lab
Problem:
Does adding soap to a penny reduce the surface tension of the water being added? OR
How does adding soap to a penny affect how many drops can fit on it?

7. Penny Lab Hypothesis Example
If soap is added to a penny, then more drops of water will fit on the penny.

8. Penny Lab Experiment Materials:
Part A: Penny, paper towel, eye dropper, 100% water solution
Part B: Penny, paper towel, eye dropper, 75% water & 25% soap solution
Part C: Penny, paper towel, eye dropper, 50% water & 50% soap solution

9. Penny Lab
Manipulated (Independent) Variable: the soap (what is added by you, the scientist!)
Responding (Dependent) Variable: number of drops of water that are able to be added (the quantitative observations collected in the data table)
* not included on Laboratory Report: Control
Control: adding water to the penny without soap

10. Penny Lab Safety Rules:
Always wear safety goggles when experimenting with chemicals (soap).
Never taste chemicals (or other substances) used for a lab experiment.
Keep lids on all containers when not in use.
Clean up spills immediately.
If any substance gets into your eyes or in a cut on your skin, notify your teacher and follow his/her directions.
Wash your hands before and after an experiment.
Clean up your lab area and materials after an experiment and return materials to their proper location.

11. Penny Lab Experiment Procedure
Rinse penny in tap water and dry completely
Place the penny on paper towel
Get solution (1, 2 or 3) and eye dropper
Use eye dropper to place drops of water on the penny (1 at a time) until water runs over edge
Record the number of drops for that trial in the table & calculate mean after 5 trials

12. Penny Lab
Data:

13. Penny Lab Results: Bar Graph of the Average of the three liquids:
*Example has 2 Bars, yours will have 3 bars, for the 3 solutions!*

14. Penny Lab Conclusion: Example
My hypothesis was unsupported. Soap decreased the number of drops of water that could be added. In Part A, the mean number of drops that could be added to the penny were….