Hydrogen Bonds

• Weakest Bonds
• Only between polar molecules.
• No exchange of electrons
• Attraction between slightly positive hydrogen atoms in one molecule and a slightly negative atom in the other molecule. Like a magnet.
• Hydrogen forms covalent bonds
• All about the bonds between molecules containing hydrogen, not hydrogen itself.

Covalent Bonds

• May or may not form polar molecules.

Non-Polar Molecule

• Always covalent
• Molecule formed via covalent bonding when atoms/electrons are evenly distributed and have similar electronegativity.

Polar Molecules

• Molecules that have a charge. Electrons are shared unevenly creating a molecule w/ a lightly positive side and a slightly negative side.

Ionic bonds are always polar

4 Properties of Water

Cohesion

• Water sticks to itself.
• Cause: Hydrogen bond is attractive
• Effects: Surface tension (Water Striders), Water transport up plants

High Heat Capacity (Temperature Stability)

• Energy has to break hydrogen bonding before water molecules can move.
• Oceans moderate climate, our body temps stay stable.

Lower Density when Frozen

• Ice floats.
• Ice forms rigid crystal structure w/ more space between molecules.
• Do to having less bonds when frozen, the molecules are less densely spaced.
  • Frozen water has 3 bonds between the molecules.
  • Liquid water has 4 bonds between the molecules.

Excellent Solvent - The Universal Solvent

• Cause: Polar water molecules surround and separate charged ions and other polar molecules.
• Effects: Dissolves salts, sugars, proteins.
  • Enabled chemical reactions in cells.
  • Transport of nutrients and waste.
• Water prefers to form other stronger bonds over the weak hydrogen bonds between itself.

"Like Dissolves Like"

• Water is polar
• Polar dissolves in polar
• Nonpolar dissolves in nonpolar
• More protons = stronger positive charge pulling on electrons = dissolves faster?

Solutions

All mixed in. Can't be separated by filtration/sight.

Solvent

The dissolving medium

Solute

What gets dissolved.

Concentrations

Amount of solute per amount of solvent.

Hydrophillic

Water-loving. Polar. Dissolves.

Hydrophobic

Water-fearing. Repels water. Doesn't dissolve.

Amphipatic

Both hydrophillic and hydrophobic. Larger molecule.

pH

The amount of H+ in a solution.

• Molecules that have H or OH can change the pH when mixed with water.
• Water breaks it's HOH structure into H+ and OH- when mixed with other molecules.
• Electrolytes help balance pH in blood.

Acidic

Larger # of H+ compared to OH- ions.

• Very reactive.
• Can donate H+ to other chemicals.

Basic

Larger # of OH- compared to H+ ions.

• Neutralizes acids.

What Regulates pH

• Proton Pumps
  • Biological mechanisms that pump out ions, like H+.
• Buffer System
  • Acts like a sponge to absorb/release excess H+ ions.

Carbon

Organic compound == has carbon.

• 4 electrons in the valence, outer shell.
  • This means it can form bonds with up to 4 other molecules.