1. Paper towel Why is paper towel able to absorb so much water?
Water adheres to the paper towel due to its polarity
In your group, cut your piece of paper towel into 4 strips (long ways)
USE PENCIL (NO pen or marker) and writer your name at the top of one strip
Color the rest with the markers anyway you wish

2. Physical Properties of Water

3. * Water statistics Covers 75% of Earth’s surface
(why understanding it is important!)
Covers 75% of Earth’s surface
97% oceans
3% freshwater
2% (of Total) in ice caps and glaciers
1% in lakes, underground, or in atmosphere (usable by humans)
Makes up 70% of the human body
92% of blood plasma
80% of muscle tissues
60% of red blood cells

4. Physical properties Water:
Is clear, colorless, odorless, and tasteless
* Colors, tastes and odors are caused by substances dissolved in the water.
Boils at 100°C
Freezes at 0°C
Density = 1.0 g/mL (at 4°C)
Water is a Polar Molecule

5. Polarity of Water
In a water molecule two hydrogen atoms form single polar covalent bonds with an oxygen atom. Gives water more structure than other liquids
Because oxygen is more electronegative, the region around oxygen has a partial negative charge.
2 corners are orbitals with unshared electrons and a weak negative charge
2 are occupied by hydrogen atoms that have polar covalent bonds

6. Water has a variety of unusual properties because of attractions between these polar molecules.
The slightly negative regions of one molecule are attracted to the slightly positive regions of nearby molecules, forming a hydrogen bond.
Each water molecule can form hydrogen bonds with up to four neighbors.
The region near the two hydrogen
atoms has a partial positive charge.
A water molecule is a polar molecule with opposite ends of the molecule with opposite charges.
Fig. 3.1
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

7. HYDROGEN BONDS
Extraordinary Properties that are a result of hydrogen bonds.
Cohesive behavior
Resists changes in temperature
High heat of vaporization
Expands when it freezes
Versatile solvent
Hold water molecules together
Each water molecule can form a maximum of 4 hydrogen bonds
The hydrogen bonds joining water molecules are weak, about 1/20th as strong as covalent bonds.
They form, break, and reform with great frequency

8. Freezing
Density of ice (at 0°C) is g/mL, so ice floats in water.
Most liquids become more dense as you cool them. However, when water freezes, a large expansion occurs.
* Where have you see H2O in repeating hexagonal patterns before?
Water “organizing” with H bonds as it freezes.
Forms hexagon shapes.

9. So ice is able to float (just barely)

10. Six Phase Changes Vaporization Condensation Sublimation Deposition
GAS
Vaporization
Condensation
B.P.
Temp (°C)
M.P.
C.P.
F.P.
LIQUID
Sublimation
Deposition
Melting
SOLID
Freezing

11. - - - - - - - - + + + + + + + + Water molecules are:
Bent (or V-shaped) O H + - O H + -
Polar: have an uneven distribution of e-
A partial (less than +1) positive charge by the H’s
A partial (< –1) negative charge by the O O H + - O H + - O H + -
Attracted to each other: (+) and (-) charges of one H2O are attracted to other (+) and (-) of another H2O
These attractions are called hydrogen bonds
(“H bonds”); occur between H2O molecules
* These are different than ionic, covalent, and metallic bonds (which occur between atoms) O H + - O H + - O H + -

12. Main Properties of Water
Polarity
Leads to Cohesion and Adhesion
Cohesion = water molecules “stick” to each other
Adhesion = water molecules “stick” to other substances

13. Adhesion
The adhesion of water leads to two other important properties:
Water as a “universal” solvent
Water only dissolves polar molecules
Capillary action

14. Universal Solvent
Solvent – a substance that dissolves another substance
What dissolves in water?
Salt
Sugar
Carbon Dioxide
Oxygen
Magic Marker (Paper towel demo)
MANY more!
For an object to dissolve in water it must also be a polar molecule!
This is why oil and water do not mix, oil is NON polar

15. Capillary Action
Capillary action = Water is able to “climb” objects against the forces of gravity
Think of the (+) and (-) ends of a water molecule acting like suction cups, and a water molecule is using them to climb up a glass building
Just like in the Paper Towel Demo

16. Cohesion
The cohesion of water molecules leads to two other important properties:
Surface Tension – the attraction between water molecules at the surface of the liquid
High Specific Heat – it takes a lot of energy to warm up water and it takes a very long time for warm water to cool off

17.  Surface Tension
Resistance of a liquid to an increase in surface area because H bonds in H2O
Ex: floating a paper clip, “water striders”, water beading on waxed car
Air
Water

18. Water resists temperature change, both for heating and cooling.
High Specific Heat
Water resists temperature change, both for heating and cooling.
Water can absorb or release large amounts of heat energy with little change in actual temperature.
At the beach, why is the sand hotter than water at noon but cooler than water at midnight? 1

19. “Water vapor forms a kind of global ‘blanket’ which helps to keep the earth warm. Heat radiated from the sun-warmed surface of the earth is
absorbed and held
by the vapor.” 1

20. Discussion Questions
Which property of water causes the cracks in the pavement in cold climates?
Why does a meniscus form on the surface of the water in a graduated cylinder?
What would happen to fish in cooler climates if the relative densities of ice and liquid water were reversed?
What property of water best describes the ability of water to clean our clothes?

21. Fill in the Graphic Organizer