1. Water
Chapter 2 p

2. Chemistry Review Bonds
Electronegative atoms atoms with a strong attraction for electrons….greedy!
Bonds
Covalent
Sharing of electrons
Strong
Equal sharing=non-polar covalent
Unequal sharing=polar covalent
Ionic
Attraction between tw0 charge atoms or molecules
Positive= CATION
Negative= Anion
Charges cancel=neutral ionic compound
Dissociates in water

3. Intermolecular forces
Hydrogen bonds (not a “true” bond)
Between the hydrogen atom in one molecule and an electronegative atom in another molecule (O, F, N)
Van der waals forces
Attraction between two polar molecules
(opposites attract)

4. Water in Biological systems
Biochemical
80% of a living organism composed of water
¾ of Earth covered in water
Humans are about 60% water
2 reasons why water is important
Major component of cells (70-95% of mass of cell)
Provides environment for aquatic organisms to live

5. Structure of Water Molecule
h2O two hydrogen atoms COVALENTLY Bonded to one greedy oxygen
Oxygen is electronegative
Unequal sharing of hydrogen’s electrons (electrons spend more time around oxygen's orbitals)=Polarity
Hydrogens in water molecule have a slightly + charge
Oxygen in water molecule has a slightly – charge
Dipole small charges on different atoms within a single molecule; unequal distribution of a charge
Water has 3 dipoles…2 positive and 1 negative

6. Hydrogen Bonding & water
Hydrogen bonds restrict movement of liquid water
Liquid water
Constantly forming and breaking hydrogen bonds
dense
Solid water
Hydrogen bonds become fixed (stuck)
Less dense than liquid
Water’s polarityHydrogen Bonding unique properties of water
Solvent properties
Thermal properties

7. Thing to Know: Role of Water in Living Organisms in reference to…..
Solvent Action
Specific Heat Capacity
Latent Heat of Vaporization

8. Solvent Properties of Water
Dipoles on water molecules enable molecules to surround other polar or ionic compounds
i.e. sodium chloride in water
Polar molecules and ions can dissolve
Good solvent
This allows water to transport substances around body of organisms
Examples:
Mammals  blood plasma is mostly water carrying glucose, oxygen, and ions (Na+)
Lymphatic, digestive, and excretory systems
Plants  nutrients from soil to all parts of the plant
Vascular tissue
Enables water to be a medium for metabolic reactions
Cytoplasm of cells
Matrix of mitochondria
Stroma of chloroplast

10. Water as a solvent in plants

11. Thermal Properties of Water
Is liquid at normal earth temperatures
H-bonds prevent water molecules from flying away from each other (like a gas)
Between 0* and 100* water is liquid
Forming and breaking h-bonds constantly
Transitory bonds
Hydrogen sulfide (h2s) similar structure to water but gas at room temp. b/c it lacks hydrogen bonds

12. Thermal Properties of Water
High specific heat capacity
Specific heat Capacity= amount of heat energy that must be added to a given mass to raise the temperature of a substance by 1* C
Large amount of energy required to raise temperature of water
Small amount needed to heat air
Large bodies of water  slow to change temperature as environment changes
Stable habitats
Inside of organisms primarily composed of water  stable environment stable body temperature
Temperature = kinetic energy
High temp = high kinetic energy
In order to increase temperature of eater, heat must not only increase the kinetic energy of the water molecules, but also break hydrogen bonds

13. Thermal Properties of Water
high latent heat of Vapourisation
DEF: a measure of the heat energy needed to vaporize a liquid (cause it to evaporate)
Liquid to gas
Liquid water to water vapour
Because of hydrogen bond, large amounts of energy are needed for vaporization to occur (H-bonds must be broken for water to escape as a gas)
Water has high latent heat of vaporization
This leads to High heat capacity
During vapourization:
Energy is transferred to water molecules as they become a gas
This means that liquid water remaining loses energy from its surroundings = cooling down of liquid water
When water evaporates, it absorbs LOTS of energy form surroundings
Evaporation of water has a cooling effect
Sweat
Panting

14. Thermal Properties of Water
high latent heat of Vapourisation
Freezing of water is the opposite of vaporization
When going from liquid water to solid ice, water molecules must lose a large amount of energy
Water molecules literally release energy when they freeze….this warms up their surroundings…
Water underneath a layer of ice warms up, preventing a lake from freezing straight through

15. Thermal Properties of Water
Freezes from the top down
Liquid water becomes dense as it cools
Water molecules lose kinetic energy and move closer together
At 4*c, water is liquid
At 0*c, water is solid
Water molecules for a lattice
Widely spaced water molecules b/c hydrogen bonds are fixed
Ice is less dense then water (it floats)
Layer of ice = insulator
Slows down the loss of heat from the water beneath it
Marine organism survive winter
Changes in density of water  currents
Maintain circulation of nutrients in bodies of water

18. Cohesive and adhesive properties
Adhesion
Water sticks to other molecules
Walls of xylem
Cohesion
Water sticks to water
High cohesion = high surface tension
Capillary Action= adhesion +cohesion

19. Water as a Reagent A reactant in chemical reactions Examples?
Photosynthesis
Energy from sun is used to separate the hydrogen ions from the oxygen in the water molecule
PHOTOLYSIS sunlight breaking up water molecules into Hydrogen ions and oxygen molecule
Hydrogen ions used to fuel the rest of photosynthesis reactions to make glucose (electrons also released to go down ETC)
Oxygen molecules are released into the atmosphere as a waste product but used as a reactant in aerobic respiration
Hydrolysis reactions
Hydro= water
Lysis= to break down
Water is used to break down larger molecules (like polysaccharides, proteins, fats)
Common in digestion

20. Water Molecule Activity
Your group needs to create at least 15 water molecules
White = hydrogen
Red = oxygen
Black Pipe cleaners = covalent bond
Colored yarn shows hydrogen bonds
Use dry erase boards to label each stage
Stages of Water to represent:
Liquid water
Solid Water
Water Vapor
A lake covered with a layer of ice
Go To table with your assigned number
Smart Phone App required: FLIPAGRAM
Materials
White paper
Red paper
Black pipe cleaners
Colored yarn
Scissors
dry erase board and marker
Smart phone
Beige paper (backdrop)

21. Practice Test Questions
Write out question and determine correct answer
11.