Water BondingWater has unusual properties

Polar Covalent Bonding of Water:Unequal sharing of electrons

(intramolecular forces)

H

H

OMeans partially +

Means partially -

OR

Hydrogen Bonds

hydrogen bond = is the attractive force between the hydrogen attached to an electronegative atom (tendency to attract electrons) of another molecule (usually O, N, F)

Hydrogen Bonding Dance (1 min)

• Youtube Polarity and Hydrogen Bonding

• (3:52)

Water Molecules

• Can bond to four other water molecules

• H+ end attracts the O-ends

Polarity of Water helps H-bonds form

• Uneven sharing of electrons• Between slightly (+) H atom to a

slightly (-) atom of a different molecule

• H-bonding of water• H- Bonding and polarity

Hydrogen Bonds between Water Molecules

•Weaker than covalent and ionic bonds

• Stronger than van der Waals

CohesionCohesion• Water is attracted

to other water molecules (similar polar molecules)

• H-bonding between water molecules hold them together

Like in drops

Cohesion is why a waterfall, a stream, a water drop forms

AdhesionAdhesion• Attraction of unlike

substances

• EX: water to the sides of a glass tube

• Drop to leafNot so much with plastic

Strong adhesion to glass

Adhesion or Cohesion?

Surface Tension-the attraction of molecules to each other (cohesion) on a liquid's surface pull inward (due to H-bonds) to create a “film” A screen showing surface tension youtube

Water molecules pull in all direction not on the surface

Surface Tension allows a Penny

or Paper Clip to float ?Surface Tension and Capillary Action?? - YouTube

Surface tension is responsible for the shape of water droplets

H-bonds pull in water to create a “film”

Water Strider

• Jesus Christ Lizard (natl geo) (1.25 mins)

• Can stand on top of water

• Water Strider on Pond Surface (44 secs)

See indentations of water strider’s feet in water.

High Specific Heat

• = the amount of heat per unit mass required to raise the temperature by one degree Celsius.

• The specific heat of water is higher than any other common substance. WHY?

• Have to break/form those H-bonds.

Phases of Water

• Describe how the molecules change (speed and spacing between molecules) as the temperature changes.

• Water Phase Change Animation (keep clicking on the “increase heat”)

• Did the water molecules break apart or did just the spacing between them change?

Note the spacing between the water molecules

Heat of fusion = needed to melt ice (solid to liquid)

Heat of vaporization = needed to evaporate to water vapor (liquid to gas)• (note how long it takes to break the H-

bonds)

Water has High Heat of Vaporization

• Takes a high temperature to evaporate, or boil water

• Need to break those

H-bonds

Water has High Heat of Fusion(Amount of heat to go from solid to

liquid)• Takes a low

temperature to freeze water (loses at lot of heat)

• Those H-bonds must form

Look at the spacing and speed of molecules in each phase

• Vision Learning (scroll down to Liquid Water and H-bonding and to Ice and H-bonding)

What’s the difference between…• Heat• Total amount of

energy of the atoms/molecules

• Temperature

• A number of the average speed of molecules

Which has more heat…10 mL of 50o C water or 100 mL of 50oC water?

• Going from water vapor to liquid to solid ice

• As heat is released the attraction between the molecules (intermolecular forces)

increases

• Going from ice to liquid water to water vapor

• As heat is taken in the attraction between the molecules (intermolecular forces) decreases

SOLID ICE LIQUID WATER WATER VAPOR

Evaporative Cooling

• The water of the surface of the skin absorbs heat to change water from liquid to gas. You feel cooler.

Water has High Specific Heat

• Takes a lot of heat to raise the temperature of water 1oC(break the H-bonds)

• This is why coastal areas have milder climates.

Kelley’s Island

• Has the same weather as northern Ohio except…

• “The still warm lake keeps us warmer in the fall, but the still cool lake gives us cold breezes in the spring.” 

Water expands upon freezing

• If water worked like other liquids, then there would be no such thing as an ice berg, the ice cubes in your soft drink would sink to the bottom of the glass, and ponds would freeze from the bottom up!

Ice forms an Open lattice

• Below 4oC (H-bonds form)

• Ice floats

• H-bonds are more stable in the solid form of water

H-bonds

Ice Expands and is Less Dense than Liquid Water

Solid

Liquid

4 oC

Water is the “Universal Solvent”

• Means it can dissolve a lot of substances due to its polarity

• Dissolving NaCl in water movie

• dissolve animation

Water is the Universal Solvent• What types of compounds are good

at dissolving?–Polar–Ionic–WHY?–Opposite charges attract–Remember: Likes dissolve likes: Polar into polar/nonpolar into

nonpolar

Aqueous Solution

• Means a solution in which water is the solvent

• Ag+(aq) + Cl-(aq) → AgCl(s)

• EXAMPLES: blood, Coke, Pepsi, urine,

Tea, coffee

Mixtures-Solutions-Suspensions

• Mixtures: 2 or more elements physically mixed (NOT CHEMICALLY BONDED)– A. Solutions: type of mixture with evenly

distributed ions throughout – B. Suspensions: Mixture of water and

undissolved material keeping the small materials suspended

Can you identify: Mixtures-Solutions-Suspensions?

Sand and Salt

Oil and Water

Groups of ElementsWhat is the difference?

What’s the difference between…

• Mixtures, solutions, suspensions, and

COMPOUNDS?

COMPOUNDS ARE CHEMICALLY JOINED…the others are physically mixed.

SOLUTIONS

• When one substance dissolves another substance.

• SOLVENT + SOLUTE = SOLUTION

• Solvent=material doing the dissolving (surrounding the ions)

• Solute=what is being dissolved

Salt Solution

Which is the solvent?

Which is the solute?

Water is solvent. Salt is the solute.

Amphipathic

• Bipolar• A molecule that is water-loving (polar)

at one end and water-hating (non-polar, like oils) at the other end

How does detergent work?

Soap has a water-loving (hydrophilic) and a water-hating end (hydrophobic).

Soap (hydrophobic end) attaches to the oil and also to the water (hydrophilic end) to wash away the oil. (animation, wait for it)

How Soap Works

Capillary ActionCapillary action – the narrower the tube the higher the water risesa.Adhesion - of water to tubeb.Cohesion-water to water (column of water)

Meniscus-water creeps up the sides of the glass tube

Note size of tube diameter and the height the liquid rises

Capillary ActionCapillary Actionor Capillarityor Capillarity

• The thinner the straw or tube the higher up capillary action will pull the water.

• Flowers and Food Coloring

• Water transport in xylem tubes youtube

• surface tension and capillary action youtube

Transpiration

• Loss of water vapor from parts of plants, especially in leaves

• ?Transpiration?? - YouTube

Explain how each of these allow water to pull up a plant?

• Cohesion ?Transpiration?? - YouTube

• Adhesion

• Transpiration

• Can you explain what is going on in this video?

• ?Flowers and Food Color Time Lapse?? - YouTube

Capillarity in Plants

• Surface Tension and Capillarity You Tube Video

• Water Transport in Plants

Solutions

• A SOLUTE is the substance to be dissolved (sugar).

• The SOLVENT is the one doing the dissolving (water).

What is the difference?

SALT SOLUTION

• Animation of Salt Dissolving in Water

• Dissolve Another Nice Animation

• When water is the solvent, the solution is called an aqueous solution.

FYI

• The solvent is defined as the substance that exists in a greater quantity than the solute(s) in the solution.

• Generally polar or ionic compounds will only dissolve in polar solvents.

Dissociation of Water (breaks into its ions)

• Acids release H+ (hydronium)

• Bases release OH- (hydroxide)

Color Pencils and Handout• Animations of Transfer of H+ ions

• Acid Strength Animations (contrast the H+ concentrations of HCl and HF)

ACIDS: release a hydrogen ion (H+) without releasing a hydroxide ion

• BASES: produce hydroxide ion (OH-) when they dissociate

ACID: increases H+

BASE: increases OH-

H+ + OH- H2O

• Why would water have a neutral pH even though the water ions dissociate?

• Equal number of H+ and OH-

Hydronium Ion = H+ Hydroxide Ion = OH-

• Animations of Acids and Bases

•

pH

• * at pH 7.0, a solution is neutral (H+ = OH-)

• * at lower pH (1-6), a solution is acidic (H+ > OH-)

• * at higher pH (8-14), a solution is basic (H+ < OH-)

pH

• = the negative logarithm (base 10) of the molar concentration of dissolved hydronium ions (H3O+). SAY WHAT?

• a low pH indicates a high concentration of hydronium ions (acidic)

• a high pH indicates a low concentration of H+ ions (basic)

• Bozeman: Acids, Bases, and pH (13:13)

• This negative of the logarithm matches the number of places behind the decimal point.

• For example, 0.1 molar hydrochloric acid should be near pH 1 and 0.0001 molar HCl should be near pH 4 (the base 10 logarithms of 0.1 and 0.0001 being 10−1, and 10−4, respectively).

• What would be the pH of 0.0000001 M H+ or 10-7?

• pH7

• pH [H+] [OH-] [H+] X [OH-]

• 0 1 X 10-0 1 X 10-14 1 X 10-14

• 1 1 X 10-1 1 X 10-13 1 X 10-14 • 2 1 X 10-2 1 X 10-12 1 X 10-14

• 3 1 X 10-3 1 X 10-11 1 X 10-14 • 4 1 X 10-4 1 X 10-10 1 X 10-14

• 5 1 X 10-5 1 X 10-9 1 X 10-14 • 6 1 X 10-6 1 X 10-8 1 X 10-14 acid• 7 1 X 10-7 1 X 10-7 1 X 10-14 neutral

• 8 1 X 10-8 1 X 10-6 1 X 10-14 base• 9 1 X 10-9 1 X 10-5 1 X 10-14

• 10 1 X 10-10 1 X 10-4 1 X 10-14

• 11 1 X 10-11 1 X 10-3 1 X 10-14

• 12 1 X 10-12 1 X 10-2 1 X 10-14 • 13 1 X 10-13 1 X 10-1 1 X 10-14

• 14 1 X 10-14 1 X 10-0 1 X 10-14

pH = -log[H+]

• At equilibrium, the concentration of H+ is 1.00 × 10-7, so we can calculate the pH of water at equilibrium as:

• pH = -log[H+]

• = -log[1.00 × 10-7]

• So pH = 7.00

pOH = -log[OH-]

• NEUTRAL

• pH+ + pOH- = 14.00 at 25°C

What is H+ when OH - = 1 x 10 – 9 M?

• pH + pOH = 14.

(pH is the negative log of the concentration of H+ ions, while pOH- is the negative log of the concentration of OH- ions.)

If the concentration of OH- is 10-9 = pH 9 Subtract that from 14 to get the pH = 14 – 9 = pH5

Two Ways to Contrast Acids and Bases

• acid: generates [H+] in solutionbase: generates [OH-] in solution

• acid: anything that donates a [H+] (proton donor)base: anything that accepts a [H+] (proton acceptor)

• Good Activities on pH understanding (The find the answers areas)

How much more?

• For every pH level lower there are 10 X’s more H+ ions

• So…… pH 2 has how many more H+ ions than pH 3?

• 10• So…pH 2 has how many more H+ ions

than pH 4?• 100

• Quia - The pH Scale

Buffer

• A substance that resists a change in pH when small quantities of acid or base are added

• (they are in the pH solutions for the duckweed)

• When acids or bases are added to pure water, they immediately produce H3O+ or OH- ions that decrease or increase the pH, respectively.

• Buffer systems resist large pH changes because added acids or bases are neutralized by the existing HA/A- (acid/base) system (equilibrium).

Where are buffers important?

• Keeping pH in the blood constant (normal blood pH is 7.4)

Homeostasis: regulation of the internal environment and to maintain a stable,

constant condition • The body is very

sensitive to its pH level, so strong mechanisms exist to maintain it.

• Discovery Health "Homeostasis"

Kidneys regulating homeostasis

• The body needs to have the consistent and proper amount of water, salt, and acid in the blood. The kidney keeps these things constant.

• If there is too much water, the kidney puts more water in the urine. If there is not enough water, the kidney puts less water in the urine.

Where are buffers important?

• Pharmaceuticals

• Industry (cleaners, cosmetics, aquarium)

• Working with enzymes

Get Extended Response Assignment

• Choose two ways the body maintains homeostasis.DUE:______________

WORTH:_________

Homeostasis AnalogyWork in Groups to Fill in Chart

Fishbowl Human Body Function

Water

Glass Bowl

Air Pump

Filters

Heater

Feeder

Fishbowl Modelof homeostasis

Fishbowl Human body Function

Water Body fluid  Internal environment

Glass bowl Skin Barrier (internal vs. external)

Fish Cells Stay alive

Air pump Lungs Keep O2 level constant (high)

Filter Kidneys Keep nitrogen wastes constant (low)

Heater Muscles Keep temperature constant (high)

Feeder Digestive system Keep nutrient levels contant (high)

Everything working together Relatively constant conditions

pH Problems• Acid Precipitation: burning of fossil fuels

(coal, oil, gas) alter pH

• Sulfur and nitrogen dioxides add to water and make sulfuric acid and nitric acid.

• Map of US area acid precipitation pH

pH Problems

• Ocean acidification = CO2 dissolved in water lowers pH (more acidic) to make carbonic acid • CO2 + H2O H2CO3

• Reduces carbonate ions

to make shells, coral,

and skeletons.

Properties of Water Lab

Overall Review

• Bozeman Properties of Water (10 minutes)