Introductory Biology

2.2 Water and Solutions

I learned the importance of water and its important properties. Water  is an major and interesting molecule to the closest order of approximation. Our body is 70% water because for about 4.1 billion years, life was underwater and we still  need water inside of us now. Water maintain homeostasis and stores heat well. Energy is needed to break hydrogen bonds between water molecules and much more energy should be added to water to make it boil/evaporate. Electronegativity is how bad the element wants electrons. Intra means within and inter means between. Intramolecular bonds are  bond between water  and lasts for millions of years are polar covalent bonds. Intermolecular bonds are bond between hydrogen and lasts for one millionth of a second and are hydrogen bonds. Intermolecular bonds are “emerging layer of complexity derived from simpler intramolecular polar covalent bond of H20″  which basically means water is different from other molecules and much of life depends on it.

Water is a medium and is for other things to be dissolved in. Water shares electrons equally, therefore it is a polar covalent bond. (poles are opposites) H2O is like little magnets since they are attracted to each other. Water is held together by hydrogen bonds and so they can break apart very quickly. Anything that is either ionic or charged will dissolve in water. Positively charged hydrogen are  attracted to negatively charged atoms and negatively charged oxygen are attracted to positively charged atoms. Cohesion form water molecules to stick to each other. And Adhesion is where water molecules stick to other charged/polar molecules. Water has surface tension because of hydrogen bonds between covalently bonded water molecules and lets the water behave like elastic.  Some organisms that can live on the water surface take advantage on the surface tension. The tubes draw water molecules up against gravity with adhesion. Some trees use this method of the tube to suck the water out of the ground and live up for more than 100 years.  Both cohesion and adhesion are very important properties of water and are taken advantage of by organisms.

Hydrogen bonds contribute to the water’s unique properties. It is important for organisms that live in the water that ice is less dense than liquid. Because ice is less dense than liquid, ice floats on top and insulates the water beneath it. If the ice was more dense than liquid, everything would freeze. When water evaporates, it takes the heat with it. Like for example, the body sweats to cool down.

Solutions are formed when many substances are dissolved by water. Polarity is important and it creates the hydrogen bonds between water molecules.  Non-polar molecules do not dissolve in the water since cell boundaries are created to avoid water. Some water molecules separate to hydrogen ions and hydroxide ions. The hydrogen ion concentration is the pH scale, which is a scale that measures the acidity. Acids are compounds that produce hydrogen ions while bases are the compounds that form hydroxide ions.Life prefers neutral, not too acid or too much of a base. The water’s molecular structure has positive and negative ends. The oxygen atom has a high electronegativity and partial negative charge.

*Entropy: measure of disorder in a system*


One thought on “2.2 Water and Solutions

  1. Yurika,

    Another excellent post for 2.2. To the closest order of approximation, we are water. I see you also picked out the word entropy, which is what happens in the absence of information, like the DNA we inherit to construct complexity.

    Mr. F.

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