1. 1. Take out water lab – we will refer to it today
Do Now 11.14
OBJECTIVES:
Identify and describe 4 special properties of water 2. Define polar molecule and Hydrogen bond.
3. Explain how electrical charges on the molecular level give water its special properties
TASK:
1. Take out water lab – we will refer to it today
2. Make a big chart on a sheet of notebook paper: “Special Properties of Water,” with 2 columns (Property and Description) and 4 rows.

2. Water is a Compound Composed of Molecules
An atomic bond is a force which joins atoms together to form a molecule H O
Atomic bond
Water H

3. O-H Polar Covalent Bonds in Water
In a polar covalent bond, electrons are shared unevenly.
Since electrons are negative, the atom that attracts electrons the most becomes a little negative, and the atom losing the electrons becomes a little positive.

4. Water is Special
Property #1: Water resists changes in temperature & phase
Demonstration
High “Specific Heat Capacity”
Related Property: high melting & boiling points

5. Related: High Melting & Boiling Points

6. Property 2: High Surface Tension, etc.

7. Property 2: High Surface Tension, etc.
Adhesion:
Water sticking to other surfaces
“Capillarity”
Cohesion:
Water sticking to Water

8. Property #3: Excellent Solvent
Water is very good at dissolving substances, particularly polar or ionic ones.
“Universal Solvent”

9. Property #4: Density Anomaly
Ice floats on water!
Water is one of only a few substances known where the solid form is less dense

10. WHY WATER HAS SPECIAL PROPERTIES:
HYDROGEN BONDS
A Hydrogen bond is a weak bond between 2 different polar molecules

11. New Bond - Hydrogen Bond: Pathetically WEAK!
A Hydrogen bond is a weak bond between 2 different polar molecules

12. Water is a polar molecule. The O-H bonds are polar covalent
Molecules with positive and negative parts are called polar molecules.
Polar molecules form hydrogen bonds

13. How H-bonds Give Water it’s Special Properties
Property
How H-Bonds Make it Happen
Temperature & Phase Stability
Energy is required to break H-bonds, reducing the amount of energy for T increase or phase change
Surface Tension, etc.
Can form H-bonds with itself or other substances, making it “sticky”
Solvent
Areas of charge arrange around charged parts of molecules
Density Anomaly
H-bond length increases as temperature drops from 4oC to 0oC

14. HOMEWORK
Complete Lab Report
No Section F