Saturday, August 31, 2013

The Properties of Water

Water...agua...H2O. However way you say it, water is the same anywhere you go. It is a life source to not only us humans, but to other organisms out there, as well. In biology, it is so much more.

Today I am going to talk about the different properties of water. There are four main properties specifically that I am going to touch on: cohesive/adhesive behavior, ability to moderate temperature, expansion upon freezing, and versatility as a solvent. However, before I begin to talk about water, I feel that I should go over some things about polarity and hydrogen bonding in order to fully understand these four properties.

Water molecules are polar. That is a fact. But why are they polar? Well, they are polar because of this little thing called unequal sharing. The oxygen in the water molecule attracts the two electrons from the hydrogen, one from each. Now, why are water molecules capable of hydrogen bonding with four neighboring water molecules? Well, for starters, a hydrogen bond has the ability to take a positive side hydrogen and a negative side oxygen, and create a bond between them. It is a weak bond, but it is still bale to keep water together. This entire process is called cohesion, but we'll get back to that later. You see, because the oxygen has a 2- charge, it can attract two hydrogen atoms from two other water molecules. And each hydrogen can attract one oxygen atom, which makes two more water molecules. In total, that makes four neighboring water molecules.    

Alright, now that we have gone over that, let's talk about cohesive and adhesive behavior. Cohesion is the ability of water molecules to be able to bond to each other. In other words, hydrogen bonding! An example of cohesion is how insects like water striders can walk on the surface of a pond without breaking the surface. Although the water strider is denser than water, it doesn't sink. This is because of surface tension and cohesice behavior. The ability of cohesion to keep water together allows the water strider to sit and walk on top of those hydrogen bonds.



Adhesion is the ability to have water attached to something else. For example, if a straw has a negative charge, water is able to bond along the straw. This is called capillary action, the ability of a water molecule to do adhesion and be able to move up a straw. The bigger the straw, the less capillary action.

Capillary action is also very important in plants. Plants transport water from the roots all the way up to the leaves. For this process to occur, both cohesion and adhesion are needed. So, the water begins to come up from the roots. In order to go up to the leaves, the water molecules stick along the plant; this is where adhesion comes into play. Cohesion occurs when the water molecules going up the plant begin to stick and attach themselves to each other. You see, both cohesion and adhesion are working here at the same time. In a tree, the water molecules would go up along the trunk tubes inside the tree until it reached the top, where the leaves are. However, not all of the water stays on the leaves. Water on a leaf can easily evaporate (turn from liquid to vapor) through the leaves' pores. Ninety percent of the water sucked in by the roots is lost at the surface of the leaves at the top of the tree or plant.

Water also has the ability to moderate temperature. It is able to resist temperature changes due to hydrogen bonding. Hydrogen bonds are able to break and be created, and in order for water to increase in temperature the hydrogen bonds must break. By doing this, the water rises to its high boiling point. The hydrogen bonds can also release and take in some energy. This entire property of water allows bodies of water to maintain temperatures by storing heat from the sun and by releasing heat when the air around it gets cooler. Different materials store different amounts of heat. Let's take gold and water, for example. Water takes about thirty times longer to heat than gold, which means it stores about thirty times more calories. 

Just as water can heat up and boil, it can also freeze! When water boils, the molecules begin to move rapidly. Furthermore, when water freezes, the molecules slow down and once the hydrogen bonds get to a certain temperature, they become stable and form a crystalline pattern. This crystalline pattern is very "open," causing the water, now ice, to become denser than liquid water. There is less mass, but the same amount of volume, and for this reason, ice floats. 


One last thing to know about water is that it is known to be a versatile solvent. It is sometimes know as the "universal solvent." Water is capable of dissolving with more materials than any other liquid. It is such an effective solvent because it readily forms hydrogen bonds. For instance, let's take a lysozyme molecule in a nonaqueous environment. The moment you add water, you get different polarities. This causes the hydrogen bonding. Your result will look like salt. The water molcules begin to split up the NaCl into smaller pieces. When an ionic compound is dissolved in water, each ion is surrounded by a sphere of water molecules, a hydration shell.

These are only some of the many things to know about water. I'm sure there is more I could tell. For instance, how hydronium and hydroxide are the products of the dissociation of water. Or how their concentration in pure water is 1e-7 M. But for now, this is all I can say. Until next time!






Basic Chemistry

Last year, the moment I finished chemistry, I rejoiced. I literally had my own little private party and blasted music in my room while throwing out anything I had that had to do with chemistry. I thought I was never going to have to deal with chemistry ever again. Going into honors biology, you can imagine my my reaction when I found out I wasn't exactly done with the subject. I immediately regretted throwing all of my chemistry related work out. Now that chemistry has become a part of my life again, there are a few basic things I need to know in order to get back into the routine.

Probably the first important thing to know is what the difference is between a proton and an electron. Well, for starters, protons have a positive charge, while electrons have a negative charge. Protons are found in the center of an atom, along with neutrons which have no charge, while electrons surround the nucleus. A proton and an electron have a charge of the exact same size, only one is negative and one is positive. Have you ever heard the saying "opposites attract?" Well, when it comes to protons and electrons, the saying is true. 

When you hear someone talking about the number of protons in a nucleus, that person is talking about the atomic number. The atomic number can be used to determine the number of neutrons in an atom, along with the atomic mass number. When you subtract the atomic number from the atomic mass number, you get the number of neutrons in an atom! Pretty simple, right? The atomic number is also used to distinguish an element. This brings me to the next important thing to know about chemistry. An element is a pure chemical substance made entirely of  one type of atom. For example, every element contains atoms containing a certain amount of protons and electrons. If you change the number of protons an atom has, you completely change the type of element it is. There are about 118 elements total. You can find these elements on a periodic table.
Elements can be classified as a metal, nonmetal, or a metalloid. Each element is represented by letter symbols. For example, the letter symbol for carbon is C, and the symbol for lead is Pb. One last thing to know about elements is that they can't be broken down by chemical reactions.

A compound, however, can be broken down by chemical reactions. Compounds are, obviously, things that are composed of more than one element, a mixture. They contains atoms of different elements combined together in a fixed ration arranged a certain way through chemical bonds. There is an endless list of compounds. Each is represented with a formula. You can classify a compound as ionic or covalent. 
Covalent and ionic bonds are formed in compounds and they are the only types of atomic bonds. A covalent bond is formed between two nonmetals when they have similar electronegativities. Neither nonmetal atom is strong enough to attract electrons from the other; therefore, for stabilization, they share their electrons with others. These bonds have a low polarity and a definite shape. An ionic bond is formed between one metal and one nonmetal. Nonmetal are stronger than metals and can attract electrons easily from metals. Just like protons and electrons, they attract because "opposites attract." Ionic bonds have a high polarity and no definite shape.













These are just some of the basic things to know about chemistry. There is so much more to be learned. In my case, there is so much more to be re-learned. So I guess it's time for me to get studying!

Friday, August 23, 2013

Doing the Milk Dance

A couple of days ago, I watched a video titled "Dancing Milk" for my honors bio class. http://www.youtube.com/watch?v=_oC1FlJBsVA After watching this video, I came up with a hypothesis as to why the milk and food coloring interacted the way they did. Soap is a type of degreaser; therefore, the dish soap is attacking the fat in the milk. My partner also brought up a good point about how the dish soap is a base, so it reacts with the acid, or the milk.

In order to prove both of our hypotheses, we created two experiments. For my hypothesis, we used coffee mate creamer, which, like the milk, contains fat. We poured 10 mL of creamer into a small plate. Next, we added a few drops of red and green food coloring. Then came time for the dish soap. My partner and I first used a diluted dish soap and the reaction looked similar to the reaction with the milk in the video. However, we then added a concentrated dish soap, and as soon as we did a clear bubble formed in the middle of the colored milk.  


We did this exact procedure two more times and continued getting the same results...



When we finished with this experiment, my partner and I decided to move on to her acid-base reaction hypothesis. This time we used vinegar as our acid and, similar to our other experiment, we used 10 mL. Just as before, we added a few drops of green and red food coloring, plus a drop of dish soap. The reaction was not as we expected. Though the color did seem to dance at first, they did not move the same way they did with the milk and creamer. We did this experiment two more times, and nothing really happened. There was no bubble formed and the movement was not the same.
My partner and I were expecting both the creamer and the vinegar to react similarly to how the milk reacted with dish soap. However, we were proven wrong and only the creamer reacted in a similar manner. So, my hypothesis about the degreaser (the dish soap) attacking the fat in the milk and being the cause of the food coloring's interaction with the milk was indeed correct.