The Wonder of Water
"Have you ever spent a long, hot day working out in the sun? What makes that kind of work bearable? Tall glasses of ice-cold water! I'm sure at one time or another you've taken a big drink of water and finished with a refreshed "Ahhh!" A drink of water is probably the best all-around thirst quencher and refresher known to man. As I am sure you already know, we can live for as many as two weeks without food, but if we were to go even a few days without water, we would surely die. Indeed, without water, life as we know it simply cannot exist."
- Excerpt taken from page 81, first paragraph of module #4, in the science textbook.
During our lab on Wednesday, October 12th, the students completed six experiments; all involving, this necessary for life, substance called water. How often do we use water? I can rattle off a whole list of things just in our daily household chores. Even though we see water as a simple, everyday naturally renewable resource that is often taken for granted, let's see what cool things the students discovered about it! Enjoy!
Getting everything set up for the first experiment
Experiment 4.1 : The Chemical Composition of Water
Austin (my apologies for no headshot) added epsom salts to tap water in a small glass beaker and stirred.
Branden then added the brand new 9-volt battery to the liquid. Immediately, the terminals starting bubbling. It took us a minute to get it just right, sitting straight up, as there was a crunchy cushion of salt at the bottom. We let that sit for about 10 minutes to allow all the air bubbles trapped inside the battery casing to escape, because extra air would effect the outcome of our experiment.
After the 10 minutes was up, Emily and Branden held a glass test tube each while they topped off each one with a bit of the solution from the beaker. They covered the openings and carefully inverted the tubes and placed them into the solution and onto the top of each of the terminals of the battery. They did try this several times before they were successful in submerging the filled tubes without any of the water pouring out. Flawless! Branden held them into place to prevent them from falling over.
What was supposed to happen : The positive terminal released oxygen into one test tube and the negative terminal released hydrogen into the other test tube. If executed perfectly, the negative side would have collected twice as much hydrogen as oxygen on the positive side. Despite what Dr. Wile presumed would happen (see pg. 83), this is exactly what happened! Good job group!!
What we learned :
We collected more hydrogen gas than oxygen gas,
which indicates there are more hydrogen atoms that oxygen atoms in a water molecule. :)
Experiment 4.2 : Water's Polarity
In this experiment, Leslie poked a hole into the bottom of a styrofoam cup, so water could flow out of it easily in a small stream. Erin and Emily used a comb and ran it through their hair in attempts to create static. They held the comb next to the stream of water in hopes the water would curve or bend. Yea, it never did. Not sure what exactly went wrong here, but I guess it might be what Dr. Wile calls experimental error. :(
We should have seen the stream of water bending toward the comb. Why should that have happened? When Erin and Emily combed their hair, the comb picked up stray electrons in their hair and as a result, became negatively charged. The negative charges on the comb attracts the positive charges in the hydrogen atoms in the water molecules. So, the water molecules all turned around so that their hydrogen atoms pointed toward the comb. Cool huh? Try this again at home to see if you can get a rise (or a curve) out of your water! :)
Experiment 4.3 : Solvents and Solutes
This was a short, simple experiment that proves that water does not dissolve everything. Austin, Emily and Branden mixed several different solids and substances into five different cups of water. Sugar - dissolved. Salt - dissolved. Canola oil - did not dissolve. Olive oil - did not dissolve.
Sugar and salt
The oils
None of us are probably surprised by the results of the experiment. But why? That is the question...and considering I would have to write several pages just to explain it, I will just leave that to you to review on your own in your textbook if you wish to, pages 91-93.
Experiment 4.4 : Comparing Solid Water to Solid Butter
The students heated butter on the stove while they filled one glass with water. They filled another glass with the melted butter. They dropped a piece of ice into the water and a piece of cold butter into the melted butter. The ice floated, but the butter melted. Why?
*Did not get a picture of this experiment because I was tending to the
butter on the stove, so I'm just adding a general picture for reference.
The molecules that made up the solid butter were closer together than the molecules that made up
the liquid butter. As a result, the solid butter pushed through the liquid butter and sank.
When water is a solid, its molecules must stay in a rigid, geometric arrangement. That rigid arrangement requires the molecules to be a certain distance apart. When water is a liquid, however, its molecules are free to move around. As a result, hydrogen bonding bonding can pull them closer together. As a result, water molecules are closer together when water is liquid compared to when water is a solid. Because of this, the ice cube could not push it's way through the water molecules, and the ice cube stayed afloat.
Experiment 4.5 : Water's Cohesion
The students filled a bowl with water, placed a paperclip on a sheet of toilet paper and gently placed that on top of the water in the bowl. When the paper sunk to the bottom of the bowl, the paperclip stayed afloat. They added a drop of dish soap and the paperclip immediately sank.
They did the same thing again, except this time, they used a bowl of vegetable oil. As soon as the paper sank, the paperclip did as well. (Only got a picture of the oil)
The phenomenon demonstrated in the experiment is called surface tension.
You can review this term and why there was a difference on page 98-99 of your textbook.
Experiment 4.6 : The Forces Between Molecules
The students used a glass vase with a smooth bottom, candle wax and water for this experiment. Noah and Austin worked together, one rubbed wax onto half of the bottom of the vase, then the other placed the vase bottom up under running water. The water on the smooth half ran off and spread out. The water on the waxed half beaded up and came together.
On the smooth side the water molecules were more attracted to the glass than themselves and therefore spread out. On the waxy side, the water molecules were more attracted to themselves than it was to the wax, so they clung together and beaded up. Pretty cool, huh?
Hope you have enjoyed the blog so far an maybe learned a few things along the way! I am looking forward to our next lab! We are talking about The Hydrosphere!
