Alrighty, so Water first.
I think we can all agree- water is pretty sweet. I mean, its the #1 reason we're able to live on planet Earth. So, what makes it so special? Why can it dissolve almost anything (without being corrosive)? Why does it comprise 70% of our body mass? Campbell (my textbook) explains that the following properties of water allow it to be the "super" substance:
- High Heat of Vaporization-- it takes a LOT of energy to get 1 gram to evaporate.
- High Specific Heat-- this one's pretty similar to the above quality- it just means it can absorb a lot of heat before actually going up a degree in temp.
- Hydrogen Bonding-- the hydrogen atoms are positive, and make bonds between the slightly negative oxygen. This pretty much makes all the other properties possible.
- Evaporative Cooling-- as the "excited" molecules evaporate, the kinetic energy loss "cools" down the substance left behind (ie our skin).
- Adhesion and Cohesion-- the first is water sticking to other things, and the second is water sticking essentially to itself.
Practical application of cohesion and adhesion-- plants draw water up through their roots using this chemical property.
- Floatation of Ice-- as water freezes it expands- preventing bodies of water from freezing solid (the ice floats to the top leaving liquid underneath).
- Universal Solvent-- Water dissolves ionic and polar substances. It's also pretty good at forming colloids with large hydrophilic molecules.
- Surface Tension-- because of the hydrogen bonding, water's surface acts like a piece of plastic wrap. This is pretty useful for a wide assortment of bugs, as seen in the picture.
I hope you're all familiar with water's dissociation into H+ and -OH. In pure water this 'reaction' happens back and forth equally (we call that equilibrium). When you start adding acids and bases, the respective levels of H+ and -OH teeter-toter, causing a shift in the pH scale. Also note that it goes by logarithms- so powers of 10, not 1.
Alrighty, next comes the Organic Chemistry stuff. I'll make this short, sweet, and to the point...
Carbon Basics:
http://www.dummies.com/how-to/content/the-basics-of-organic-chemistry.html
Functional Groups 'Cheat Sheet':
http://www.dummies.com/how-to/content/organic-chemistry-1-for-dummies-cheat-sheet.html
Most of this chapter was about the role Carbon plays in forming the 'molecules of life'. In other words, it was an overview of the practical molecular 'uses' of carbon (just as the previous chapter highlighted useful properties of water and the respective application).
Something I found VERY interesting-- Carbon is what it is because of it's four valence electrons. It's ability to make four bonds allows hydrocarbons, ketones, alkenes, alcohols, etc. to be formed. We are carbon based life forms. That being said- researchers are now looking into Silicon based life. This compound also has four valence electrons and may have similar bonding abilities as carbon. Hmm... Silicon based aliens? Food for thought.
