1. pH and Water Lab Read pages 13-17 in lab manual disassociation
Water molecule
Hydroxide ion
Hydrogen ion

2. UNIQUE PROPERTIES OF WATER
2/3 of Earth is covered with water
Sometimes occurs in all 3 states
Liquid, solid, gas

3. Heats & cools slowly
= high _____________
Amount of energy required to heat up
‘Moderates’ Earth’s environments
‘Solvent of life’
Dissolves & carries molecules within organisms
Solvent = liquid portion of a mixture
Solute = what is dissolved in the solvent

4. - + Water is a ____ molecule Has opposing charges on each end
Result of a polar _______________
O has greater _________________ than H
Pulls electrons toward it
Shared electrons hover closer to oxygen
Polar molecules mix best with other polar molecules
Lipids are non-polar
e.g., water and ___ do not mix well

5. Water molecules attach to each other with __________ bonds
Weak, short-lived, ______________
Hydrogen bond

6. Water’s hydrogen bonds at different temperatures:
Room temp.: constantly break and reform = _____
Below 32oF: stable & _________ = ice
Above 212oF: break entirely = ___ (vapor/steam)

7. Cohesion When ___ molecules cling together E.g., Surface tension
The membrane-like surface of liquids

8. Adhesion When _______ molecules cling E.g, Capillary action
Water ‘wicks’ to sides of containers
A ________ is caused by both cohesion & adhesion

9. Water disassociates into charged ions
(H2O)
Hydroxide ion
(OH-)
Hydrogen ion
(H+)
Solutions can have an abundance of free OH- or H+
Measured as ___

10. pH: the relative _______ of OH- & H+
Measured on a scale of 0 to 14, __ = “neutral”

11. Lab Procedures pH of common household solutions
Test the pH of various solutions
Assign several to each group member
No single person should test all solutions
Litmus paper will change color according to pH
Dip litmus paper into solution using forceps
Do not touch the paper with your hands
Hand salts will bias your results
Record results within 5-6 seconds

12. Buffers Buffers “tie-up” excess free ions
Many biological fluids are “buffered”
Why?
Compare buffering ability of milk to water
Rinse beakers before filling
Measure initial pH of each
Add 5 drops of dilute acid to each
Stir
Return dropper to correct vile
Measure and record new pH
Add 10 drops of dilute base

13. The energy required to change temperature
Specific Heat:
The energy required to change temperature
Compare specific heat of water and alcohol:
1) Bring water and alcohol to equally low temperature
Record that temperature
2) Heat water and alcohol in hot water bath
Record changes in temperature over time
3) Cool water and alcohol in ice bath
water
alcohol

14. “Mystery” movement of liquids up a tube
Capillary action
“Mystery” movement of liquids up a tube
Compare capillary action of water and alcohol
Compare different liquids
with one tube diameter
Compare different tube
diameters in one liquid