Polarity of Molecules
Non-Polar Molecule
- Can't be formed by ionic bonds due to the transfer of electrons resulting in polarity.
- Molecule formed via covalent bonding when atoms/electrons are evenly distributed and have similar electronegativity.
Polar Molecules
- Molecules that have a charge.
- Ionic bonds always form polar molecules.
- Covalent bonds may or may not form polar molecules.
- Electrons are shared unevenly creating a molecule w/ a lightly positive side and a slightly negative side.
Hydrogen Bonds (Van der Waals Forces)
- Weakest Bonds.
- No exchange of electrons.
- Only between polar molecules.
- Hydrogen forms covalent bonds.
- All about the bonds between molecules containing hydrogen, not hydrogen itself.
- Attraction between slightly positive hydrogen atoms in one molecule and a slightly negative atom in the other molecule.
- Like a magnet.
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)
- Cause
- Energy has to break hydrogen bonding before water molecules can move.
- Effects
- Oceans moderate climate.
- Our body temps stay stable.
Lower Density when Frozen
- Due 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.
- Cause
- Ice forms rigid crystal structure w/ more space between molecules.
- Effects
- Ice floats.
Excellent Solvent - The Universal Solvent
- Water prefers to form other stronger bonds over the weak hydrogen bonds between itself.
- Cause
- Polar water molecules surround and separate charged ions and other polar molecules.
- Effects
- Dissolves salts, sugars, proteins.
- Enables chemical reactions in cells.
- Transport of nutrients and waste.
"Like Dissolves Like"
- Water is polar
- Polar dissolves in polar
- Nonpolar dissolves in nonpolar
- More protons = stronger positive charge pulling on electrons = dissolves faster?
Nature of Solutions
- Solutions
- All mixed in. Can't be separated by filtration/sight.
- Solvent
- The dissolving medium
- Solute
- What gets dissolved.
- Concentration
- Amount of solute per amount of solvent.
Nature of Molecules
- Hydrophilic
- Water-loving. Polar. Dissolves.
- Hydrophobic
- Water-fearing. Repels water. Doesn't dissolve.
- Amphipathic
- Both hydrophilic 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.
- Acidic
- Larger # of H⁺ compared to OH⁻ ions.
- Can donate H⁺ to other chemicals.
- Very reactive.
- Basic
- Larger # of OH⁻ compared to H⁺ ions.
- Neutralizes acids.
Electrolytes when dissolved in water break apart into cations and anions. They help balance pH in blood.
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
- 4 electrons in the valence, outer shell.
- This means it can form bonds with up to 4 other atoms.
- Organic Compound
- A compound containing Carbon.