Make observations about the penny. Purpose: To gain a better understanding of surface tension by observing the special properties of water. Do Now: Make observations about the penny. What are some of the characteristics the Heads side of the penny have? What are some of the characteristics the Tails side of the penny have? (How do they feel different? How do they look different?)

Properties of water Cohesion Water molecules are attracted to other water molecules. The oxygen end of water has a negative charge and the hydrogen end has a positive charge. The hydrogens of one water molecule are attracted to the oxygen from other water molecules. This attractive force is what gives water is cohesive properties.

Properties of Water Surface Tension Surface tension is the name we give to the cohesion of water molecules at the surface of a body of water. The cohesion of water molecules forms a surface “film” or “skin.”

What are we changing during this experiment? Experiment Design What are we changing during this experiment? What are we testing or measuring in this experiment? The side of the penny. (Heads and Tails) This is our Independent Variable (IV) How many drops of water that can fit on the penny. This is our Dependent Variable (DV)

Create a hypothesis using the If/then/because format. If you need help creating your hypothesis use the guiding questions found at your table.

Procedures Obtain 4 small pieces of paper towel, one penny, one pipette, and one beaker with 50 mL of water. Wipe the penny clean with the paper towel and place the penny heads side up on one small piece of paper towel. Pipette small drops of water on the penny, counting each drop. Keep adding drops until the water bubble bursts and runs onto the paper towel. Not counting the final drop that made it burst, record the number of drops that fit onto the heads side of the penny. Record the results in data table 1. Repeat the same procedure (steps 2-5) for the heads side again. Repeat the procedure two more times, but now use the tails side of the penny. Record those two trials.

Procedures Continued Calculate the average number of drops for the heads side of the penny. Record the results in data table 1. Calculate the average number of drops for the tails side of the penny. Record the results in data table 1. Side of Penny Trial 1 Trial 2 Averages Heads   Tails

Conduct Your Experiment Work Period Conduct Your Experiment

Close/Share Compare your data with the other people at your table. Class discussion to share results. Clean up

In your own words, explain surface tension. Exit Ticket In your own words, explain surface tension.