1. Chemistry Review & Water
Chapters 2 & 3

2. YOU MUST KNOW The 3 subatomic particles and their significance
The types of chemical bonds and how they form
The importance of hydrogen bonding to the properties of water
Four unique properties of water and how each contributes to life on Earth
How to interpret the pH scale
How changes in pH can alter biological systems
The importance of buffers in biological systems

3. Bonding Review Covalent Bonds Atoms share electrons
Can have single, double, triple bonds
Relatively strong bonds
Many different types for specific kinds of molecules (ex. peptide, glycosidic, phosphodiester)
Can be polar or non-polar (are electrons shared equally?)

4. Bonding Review Ionic Bonds
Atoms gain/lose electrons, resulting in charges which attract them to each other
Generally the strongest bonds

5. Bonding Review Van der Waals Interactions (hydrophobic interactions)
Weak connections, break and reform, as a result of asymmetrical distribution of electrons (since electrons are always moving)
aka intermolecular forces

6. Water Polarity: Uneven distribution of charges around a molecule
Hydrogen side of water molecule is slightly positive while oxygen side is slightly negative
Attraction between positive side of one water molecule and negative side of next = Hydrogen bond

7. Water 1. Cohesion & Adhesion
Cohesion - Water molecules are attracted to other water molecules

8. Cohesion - Water molecules are attracted to other water molecules Water forms into droplets (which join together when close)

9. Cohesion - Water molecules are attracted to other water molecules Water forms into droplets (which join together when close) Water has strong surface tension (remember penny lab?)

11. Cohesion - Water molecules are attracted to other water molecules
Water forms into droplets (which join together when close)
Water has strong surface tension (remember penny lab?) Water can move as a column in plants
Go to 1:55

12. Water
Adhesion - Attraction between water molecules and other types of molecules
Also at play in movement of water in vascular plants (capillary action) - Once water moves into the vascular tissue, adhesion keeps it from dropping back down

13. Water High Specific Heat
The amount of heat required to raise or lower the temperature of a substance by 1degree C
Makes temperature of Earth stable (ocean temps stable)
Helps plants and animals maintain temperatures
Evaporative cooling

14. Less dense in solid form
Water
Less dense in solid form
Ice floats – insulates large bodies of water to keep them from freezing entirely (life can survive the winter)
Forms habitat for some species

15. Water 4. Solvent Capable of dissolving an abundance of other molecules
Makes it extremely valuable in transporting molecules in your body
Water being transported by cohesion and adhesion in plants is carrying dissolved substances everywhere it goes
Blood is composed mainly of water – carries dissolved substances around your body (glucose, ions, amino acids)
Also makes it an excellent medium for metabolic reactions
*Remember
Solvent = substance doing the dissolving
Solute = substance that gets dissolved
Together they make a solution

16. Water Hydrophilic molecules – molecules that dissolve in water
Generally polar (like likes like)
Ex. glucose and other carbohydrates, ions such as sodium (Na+, Ca++, Cl-)
Hydrophobic molecules – don’t dissolve in water
Generally non-polar
Ex. Lipids, methane

17. pH

18. pH Buffers Weak acids/bases that minimize changes in pH
Ex. Carbonic acid (H2CO3) – in living systems
Moderates pH changes in blood plasma

19. Molarity (M)
Number of moles (6.022 x1023 molecules) per liter of solution (***Note that it is L of solution, NOT solvent!)
How we quantify the concentration of a solution

20. Molarity Sample Problem:
How many grams of sucrose (C12H22O11) would you add to water to make 0.75L of a 0.6M aqueous solution?

21. Molarity Step 1: Determine the molecular mass of sucrose.
C12H22O11 - (12 atoms of carbon x 12) + (22 atoms of hydrogen x 1) + (11 atoms of oxygen x 16) = (144) + (22) + (176) = 342g/mol

22. Molarity Step 2: Solve for number of moles in the solution
Molarity (M) = m (moles)/V (volume in liters)
0.6M = m/0.75L
m = 0.45 moles

23. Molarity Step 3: Determine g in 0.45 moles 342 g/mol = X/0.45 mol
X = 154g