For the first lab, a group of people, including myself, tested how many drops of water would fit on the surface of a penny. To control the size of the drops, we used a plastic water dropper. We then repeated the experiment using alcohol instead of water. The lab results are displayed below.
Name Water Alcohol
Ana 102 38
Skylar 101 48
Kalee 27 58
During the experiment, the water formed one drop on the penny. We discovered that this occurred due to surface tension, cohesion, and adhesion. As the water drops were placed on the penny, the drops stuck together and to the surface of the penny. The surface tension was able to keep the droplet together and not spill off the side of the penny.
http://www.factfixx.com/wp-content/uploads/2011/06/surface-tension-water-penny.jpg
What made the water cohere so well? The water was able to cohere due to the positive and negative charges found in H2O molecules. Has anyone ever told you that opposites attract? The positive and negative charges found in H2O attract, causing the molecules to form hydrogen bonds and create a "clump". A visual example is shown below.
http://healingearth.sites.luc.edu/sites/default/files/styles/chapter_photo/public/images/3D_WaterHbnds_wiki.jpg?itok=Sq8fyeJI
When we repeated this experiment with alcohol, we found that it did not cohere or adhere as well as water did. This was because alcohol molecules do not have the type of makeup that would allow them to form bonds as easily as water.
http://2012books.lardbucket.org/books/principles-of-general-chemistry-v1.0/section_08/46eb65b7be278a0cd7b95b9e59b49ebb.jpg
As you can see, alcohol molecules do not "pair up" as well as water. The bonds they form are much weaker than water, causing them to break easily and evaporate.
Because water coheres so well, it is able to travel through live organisms. For example, human bodies contain 60% water. We need water in order to regulate body temperature, distribute nutrients, keep mucus membranes moist, and flush waste from our system. So how does water reach every part of the human body to be able to accomplish these tasks? This occurs because of coherence and adherence. When you drink water, it enters and is absorbed into your system. It adheres to the walls of your body, while cohering to the other water molecules in your system. This forms a tight, "locked" system. The water stays together, then evaporates as you perspire. This water then needs to be replenished. Though humans can survive for weeks without food, they can only survive a few days without water.
The second lab we did worked with how water adheres to different surfaces. For this lab, we placed one large drop of water on a square section of waxed paper. We then tried to separate the drop of water using a wood toothpick.
https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh4vlQtgQ7eGV1hPn3WMBtXlk85HVuTUfpW2MTKvTce8H0hS_UozTsxuRkPbqRIBuH56LNgq3YTyKEd8K83uJ16ajqoVx_VxXMb9OiG0hyphenhyphenHEOM6Bi5XdeoXkqX-bGO-qnK8iROOgGOu1qE/s1600/photo.JPG
We found that the water did not adhere well to the waxed paper and simply moved when touched by the toothpick. This proved that the cohesion of water was stronger than its adherence to the waxed paper and toothpick.
For the last experiment, we tried to transport water from one glass beaker to another using only a piece of string.
http://images.kiwicrate.com/live/main/tstep/iea9268cb43f5/abc2e714f3e7.jpg
When the water traveled along the string, it adhered well to it, using it as a path to the other beaker. The surface tension of the water was strong enough to where the water did not spill. The water also cohered to its other molecules, which allowed it to flow evenly and naturally.
Through all of these labs, we were able to test the amazing properties of water and how these properties play into everyday life. We discovered how water coheres ad adheres, how surface tension allows it to travel without "breaking" and how hydrogen bonds connect everything together.
No comments:
Post a Comment