What makes water so What makes water so special?special?

WaterWater

•A water molecule (H2O), is made up of threethree atoms --- one oxygen and two hydrogen.

H

HO

So…what makes water so So…what makes water so special?special?

Water is Polar!!!!Water is Polar!!!!

• The oxygenoxygen end “acts” negativenegative• The hydrogenhydrogen end “acts”

positivepositive• Causes the water to be POLAR, POLAR,

like a magnet.like a magnet.

Hydrogen Bonds Exist Hydrogen Bonds Exist Between Water MoleculesBetween Water Molecules• Formed between a Formed between a

highly highly Electronegative atom Electronegative atom (like oxygen in (like oxygen in another water) of a another water) of a polar molecule and a polar molecule and a hydrogenhydrogen

• Weak bond, but Weak bond, but strong in great strong in great numbers numbers (ask about Crocodile (ask about Crocodile Dundee)Dundee)

Interaction Between Interaction Between Water MoleculesWater Molecules

Negative Oxygen Negative Oxygen end of one water molecule is end of one water molecule is attracted to the attracted to the Positive Hydrogen Positive Hydrogen end of end of

another water molecule to form a another water molecule to form a HYDROGEN HYDROGEN BONDBOND

What are What are the the

PropertieProperties of s of

Water?Water?

Properties of WaterProperties of Water

•CohesionCohesion

Properties of WaterProperties of Water

•CohesionCohesion•AdhesionAdhesion

Properties of WaterProperties of Water

•CohesionCohesion•AdhesionAdhesion•High Specific HeatHigh Specific Heat

Properties of WaterProperties of Water

•CohesionCohesion•AdhesionAdhesion•High Specific HeatHigh Specific Heat•High Heat of High Heat of VaporizationVaporization

Properties of WaterProperties of Water

•CohesionCohesion•AdhesionAdhesion•High Specific HeatHigh Specific Heat•High Heat of High Heat of VaporizationVaporization

•Less Dense as a SolidLess Dense as a Solid

CohesionCohesion• Attraction between particles of Attraction between particles of

the same substance the same substance (( why water why water is attracted to itself)is attracted to itself)

• Results in Results in surface tensionsurface tension (a (a measure of the strength of measure of the strength of water’s surface)water’s surface)

Cohesion …Cohesion …

Helps insects walk across water, but how is it helpful to people?

AdhesionAdhesion• Attraction between two different Attraction between two different

substancessubstances..• Water will make Water will make hydrogen bonds with hydrogen bonds with

other surfacesother surfaces such as glass, soil, such as glass, soil, plant tissues, and cotton. plant tissues, and cotton.

• CapillaryCapillary actionaction-water molecules will -water molecules will “tow” each other along when in a thin “tow” each other along when in a thin glass tube.glass tube.

Adhesion Causes Adhesion Causes Capillary ActionCapillary Action

Which gives water the ability to “climb”

structures

High Specific HeatHigh Specific Heat• Amount of heatAmount of heat needed to raise or needed to raise or

lower lower 1g1g of a substance of a substance 1° C1° C..

• Water Water resistsresists temperature changetemperature change, , both for heating and cooling.both for heating and cooling.

– Would you rather walk on sand or in Would you rather walk on sand or in water on a beach on a hot summer day?water on a beach on a hot summer day?

– Which would be warmer that night? Which would be warmer that night? Why?Why?

High Heat of High Heat of VaporizationVaporization

• Water vapor Water vapor forms a kind of global ‘‘blanket” which helps to keep the Earth warm.

• Heat radiated from the sun Heat radiated from the sun warmed surface of the earth is

absorbed and held absorbed and held

by the vaporby the vapor.

Water is Less Dense as Water is Less Dense as a Solida Solid

•Which is ice and which is Which is ice and which is

water?water?

Solutions & Solutions & SuspensionsSuspensions• Water is usually part of a Water is usually part of a mixturemixture..

• There are two types of mixtures:There are two types of mixtures:– SolutionsSolutions: substance dissolves in : substance dissolves in liquidliquid

– SuspensionsSuspensions: substance suspends in : substance suspends in liquidliquid•Come up with examplesCome up with examples

SolutionsSolutions

Water is the solvent, salt is the solute

salt water is the solution

SuspensionsSuspensions

• Substances that don’t dissolve don’t dissolve but separate but separate into tiny pieces.

Acids, Bases and pHAcids, Bases and pHOne water molecule One water molecule is made of two is made of two

ions, ions, (H+) (H+) and a Hydroxide Ion and a Hydroxide Ion (OH-)(OH-)

Hydrogen Ion Hydroxide IonHydrogen Ion Hydroxide Ion

Acid Acid BaseBase

H2O H+ + OH-

Acids and BasesAcids and BasesAcid: A solution with lots of A solution with lots of HH++ ionsions• pH 0 up to 7 is acid (acidic)0 up to 7 is acid (acidic)

Base: A solution with lots of A solution with lots of OH- ions ions• pH above 7 – 14 is babove 7 – 14 is basic

(alkaline)

• Indicates the percent of Hpercent of H++ ions ions

• Ranges from 0 – 140 – 14• pH of 7 is neutral7 is neutral

• Each pH unit represents a factor of 10X 10X change in concentration– pH 3 is 10 x 10 x pH 3 is 10 x 10 x

10 (1000x) 10 (1000x) stronger than a stronger than a pH of 6pH of 6

The pH Scale…acidsThe pH Scale…acids

The pH Scale…basesThe pH Scale…bases

BuffersBuffers• Weak acids or bases that react Weak acids or bases that react

with strong acids or bases to with strong acids or bases to prevent sharp, sudden changes prevent sharp, sudden changes in pH in pH (neutralization).(neutralization).

• Produced naturally by the body Produced naturally by the body to maintain to maintain homeostasishomeostasis

Weak AcidWeak Acid Weak BaseWeak Base

Human biology and pH

• Your blood maintains a pH of 7.35 – 7.45 (slightly basic)– Balance is maintained by buffers

in blood, breathing, and urinating

• The human vaginal canal has a pH of 3.8 – 4.5…Why?

Write down 3 questions you have.

Quick Quiz

Quick Quiz1.Draw a water molecule with labeled atoms and charges.

2.What is the property called that describes water sticking to itself?

3.What makes a solution acidic?

4.What has a higher pH, bleach or lemon juice?

5.Why do we sweat?

Quick Quiz1.Draw a water molecule with labeled atoms and charges.

Quick Quiz1.Draw a water molecule with labeled atoms and charges.

2.What is the property called that describes water sticking to itself?

Quick Quiz1.Draw a water molecule with labeled atoms and charges.

2.What is the property called that describes water sticking to itself?

3.What makes a solution acidic?

Quick Quiz1.Draw a water molecule with labeled atoms and charges.

2.What is the property called that describes water sticking to itself?

3.What makes a solution acidic?

4.What has a higher pH, bleach or lemon juice?

Quick Quiz1.Draw a water molecule with labeled atoms and charges.

2.What is the property called that describes water sticking to itself?

3.What makes a solution acidic?

4.What has a higher pH, bleach or lemon juice?

5.Why do we sweat?