Name: Melia ROkosh BLK: D

Penny Lab
Purpose:To determine how many drops of water fit on one side of a
penny.
Hypothesis:If the liquid placed on the penny decreases the surface cohesion, the penny will hold less drops of water, then without the soap solution, because the soap solution will weaken the bond between the hydrogen and oxygen atoms, and make it harder for the drops of water to stay on the penny.

Materials:

-One 100 mL beakerfilled with 50 mL of soap solution

-One dropper

-One 50 mL beaker filled with 25 mL of H2O

-Eight pennies

-8 paper towels

-One tweezer

Procedure:

Part A: Perform a CONTROL test for comparison with later results.

Step 1: Rinse a penny in tap water and dry completely.

Step 2: Place the penny on paper towel.

Step 3: Use an eye dropper to place drops of WATER on the penny (one at a time) until ANY amount of water runs over the edge of the penny.

Step 4: Record the number of drops for that trial in the table.

Repeat Steps 1 - 4 three more times before calculating your average.

Number of drops
TRIAL 1 / Number of drops
TRIAL 2 / Number of drops
TRIAL 3 / Number of drops
TRIAL 4 / AVERAGE Number of drops
17 drops / 26 drops / 16 drops / 33 drops / 23 drops

Part B: Perform tests with the TESTING LIQUID.

Step 1: Start with a “clean” penny. Rinse the penny in tap water and dry completely. Be sure to remove asmuch residue as possible - without using soap!

Step 2: Hold the penny with the tweezers provided, then dip it into the TESTING LIQUID. Allow extra liquid

to drip off the penny into the container before proceeding to the next step.

Step 3: Place penny on dry spot on a paper towel. Place drops of WATER on the penny (one at a time) untilANY amount of water runs over the edge of the penny.

Step 4: Record your observations and the number of drops for that trial in the table.

Repeat Steps 1 - 4 three more times before calculating the average.

TRIAL 1 / TRIAL 2 / TRIAL 3 / TRIAL 4 / AVERAGE
7 drops / 9 drops / 8 drops / 5 drops / 7 drops

Observations:

Experiment Without Soap solution:
/ Experiment With Soap solution:


In this picture, the first trail of the control groups experiment is being conducted, and a student is placing the drops of water in the middle of a dry and prewashed penny without the soap solution. / In this picture, the second trail of the experimental group is being conducted, and a student is placing the drops of water in the middle of a penny with the soap solution.

Results:

Group # / Average Number of water Dropson the Control Penny / Average Number of Drops on the
Penny submersedin the soap solution
Group One / 20 drops / 9 drops
Group Two / 25 drops / 8 drops
Group Three / 26 drops / 6 drops
Group Four / 23 drops / 7 drops
Group Five / 22 drops / 9 drops
Group Six / 14 drops / 5 drops
Class Average: / 22 drops / 7 drops

Conclusion:

This experiment investigated whether or not soap solutions have an effect on a drop of water’s ability to stay on a single penny. In order to study this problem, drops off water were put onto the penny through a dropper, firstly an experiment was conducted without a soap solution, and then a second experiment was conducted, except the penny was dipped in the soap solution. After the two experiments, the results were compared to see how they differed. Results showed that a soap solution does in fact break the bond between a hydrogen and oxygen atom. The average drops of water that could fit on a penny without the soap solution was 23 compared to the 7 drops that were able to fit onto the pennies with the soap solution. This proved that the hypothesis: “if the liquid placed on the penny decreases the surface cohesion, the penny will hold less drops of water, then without the soap solution, because the soap solution will weaken the bond between the hydrogen and oxygen atoms, and make it harder for the drops of water to stay on the penny” was supported, because the pennies without the soap solution proved its ability to hold the most amount of water droppings. The soap solution weakened the cohesive properties between the water molecules attraction to other water molecules. In addition, the soap solution reduced the surface tension at the surface of the body of water, and the “film” formed by the water molecules cohesion was weakened. For the most part, all of the group’s results were around the same, and the average was 22 without the soap solution and 7 with it, although there were some groups who brought down the average. Some possible reasons for receiving different results could be that not all the soap solution was washed off of the pennies before beginning the experiment, the table was shaking while the droppingswere being dropped onto the pennies or the droppings were not placed in the center of the penny, so they fell off faster due to the physics of it. Different ways to extend this experiment could be to test this hypothesis with a penny that has been dipped in water, another could be to use a larger coin like a loonie or a toonie, in order to see if a larger coin can hold a larger amount of water droppings. Questions about the experiment include: how can a single penny hold so many drops of water? How does the soap solution weaken the bond between the hydrogen and oxygen atoms? Are there types some soap solutions that make the bond between the hydrogen and oxygen atoms stronger? Finally, if the experiment was repeated a few changes that could be made to improve the experimental design would be to change the independent variable. This experiment’s hypothesis was supported, but what if the same experiment was conducted using another variable such as: a carbonated liquid, a sugary substance or hot water instead of cold water.