1. Honors Bio Ms. Napolitano
Basic Chemistry
Honors Bio
Ms. Napolitano

2. Water is everywhere! The Earth is ~71% water
The human body is made up of about % water
Water is a polar molecule
Molecules of water are held together by hydrogen bonds

3. Properties of Water
Cohesion –the attraction of H2O molecules to other H2O molecules due to hydrogen bonding
Adhesion – attraction of H2O to other substances
Capillary Action - ability of H2O to move within narrow spaces against gravity
Surface Tension – cohesive forces at the surface of H2O

4. Properties of Water Expansion upon freezing
Solid state is less dense than liquid state
Begins to expand at 4°C
Floating ice creates insulation for underneath, allows for life in aquatic ecosystems

5. Properties of Water Universal solvent
Solute – substance being dissolved
Solvent – dissolving agent
Solution – homogenous mixture of 2 or more substances
Aqueous solution – water is the solvent
Water forms a hydration shell around ionic compounds
Water dissolves polar compounds
Hydrophilic – “water loving”, affinity for H2O
Hydrophobic – “water fearing”, repels H2O

6. Properties of Water Moderate Temperature
Specific Heat – amount of heat that must be absorbed or lost for 1g of substance to change 1°C
Calorie – amount of heat to raise 1g of water by 1°C
Water has high specific heat: 1 cal/g/°C
Due to hydrogen bonding
Water has high heat of vaporization
Moderates climate
Evaporative cooling prevents organisms from overheating

7. 10/21 - Do Now
Please take out your homework and a piece of notebook paper.
Grab your clickers!

8. Properties of Water Moderate Temperature
Specific Heat – amount of heat that must be absorbed or lost for 1g of substance to change 1°C
Calorie – amount of heat to raise 1g of water by 1°C
Water has high specific heat: 1 cal/g/°C
Due to hydrogen bonding
Water has high heat of vaporization
Moderates climate
Evaporative cooling prevents organisms from overheating

9. Hydration Sphere

10. Hydration Sphere

11. pH Dissociation: the breaking apart of 2+ molecules
Usually capable of recombining
In water, one H+ ion shifts from one molecule to the other

12. pH Acid – increases H+ concentration of a solution HCl  H+ + Cl-
H2CO3  HCO H+
Base – reduces H+ concentration of a solution
NH3 + H+  NH4+
NaOH  Na+ + OH-
Acids and bases that dissociate completely in water are called strong acids and strong bases, respectively.

13. The pH Scale Measure of H+ concentration
pH is lower as H+ concentration increases
pH is higher as H+ concentration decreases
pH 7 = neutral

14. Buffers Many bodily processes are pH specific
Most living cells have pH of ~7
Buffers – substances that minimize change in H+ and OH- concentrations in a solution
Accept or donate H+ ions
Usually contain a weak acid and corresponding base