I arrived at my biology class several minutes earlier than usual. Sitting near the back of the class, I noticed that there were hardly any people in my vicinity. This made me feel uneasy and I considered moving to a more populated area. But, as I expected, by the time class had started, almost all of the seats were full. Someone behind me asked his neighbor about what he missed from the previous class and I began to shuffle through my notes in an attempt to remember what we had done. I saw several doodles and they looked pretty good. This prompted me to work on a few drawings until we started taking notes.
As the class took notes, several students asked questions about the material we were covering. I noticed that there were only three people who regularly ask questions. I came to the conclusion that these people didn’t have trouble understanding what we were learning, but were trying to impress the teacher.
I noticed that a girl two rows ahead of me had a tattoo behind her ear. It crudely depicted a house with two letters inside of it. My focus temporarily strayed from note taking and I began to ponder what this tattoo could mean.
By the time we had finished taking notes, I was very hungry. As the class came to a close, this hunger occupied most of my thoughts. Before long, we were dismissed and I packed up my things, ready for lunch.
Water is a very versatile molecule. As you probably know, it essential to life on Earth. Its molecular formula is H2O, which means it consists of two hydrogen atoms and one oxygen atom. Water is classified as a polar molecule because it is unequally charged. This imbalance of charge allows water molecules to link via Hydrogen bonds. Below is an example of how water molecules interact with one another.
These hydrogen bonds contribute to some of water’s awesome properties. For instance, H-bonds directly influence water’s ability to float when frozen. When water reaches zero degrees Celsius, it undergoes a phase change from liquid to solid. In their solid state, water molecules form a crystal lattice. (For reference, see the photo below.) This crystal lattice takes up more space than liquid water, but weighs the same. So, because of its crystal lattice, solid water is less dense than liquid water, which means it floats. In lakes, rivers, and other bodies of fresh water, ice insulates marine life from the cold. If ice didn’t float, large amounts of marine life would die every winter.
Another one of water’s interesting qualities is its ability to dissolve many compounds. Because water is a polar molecule, it dissolves other polar molecules. As a rule of thumb, “like dissolves like.” This means that polar solvents dissolve polar solutes and non-polar solvents dissolve non-polar solutes. Water dissolves other polar substances in a very interesting way. The positively charged regions of water surround the negatively charged regions of the solute while the negatively charged regions of water surround the positively charged regions of the solute. This creates what is called a hydration shell around the solute. Water’s unique capabilities as a solvent make many chemical reactions possible. These chemical reactions are very important and ultimately allow for us to survive.