Chapter 17: Water and Aqueous Systems - PowerPoint Presentation

Slide1

Chapter 17: Water and Aqueous Systems

Ms. Knick

HAHS

CHEM 1BSlide2

Chapter 17 Section 1

Liquid Water and Its Properties:

-it is foundation of all life

-makes up 70% of body of humans

-can exist in all three phases

-Water is

polar

-bonding e- shared unequally

*caused by

electronegativity

diff.Slide3

-Many properties of water are due to hydrogen bonding

-water has strong attractions between the hydrogen atoms and oxygen atoms of different water molecules and it is very

difficult to break these bonds

Slide4

Properties Resulting From H-Bonding

h

igh surface tension

Low Vapor Pressure

high heat of vaporization

high boiling pointSlide5

Surface Properties

-surface of water acts as a skin

--this is explained by

surface tension:

-inward force or pull that tends to minimize the surface area of a liquid

-holds water in shape of sphere

-can be reduced by adding a

surfactant

: interferes with hydrogen bonding

ex- soapSlide6

Low Vapor Pressure

vapor pressure

- pressure right above the surface of a liquid, caused by molecules escaping to gas phase

-b/c of H-bonding the molecules cannot escape as easily so vapor pressure is low

-if not lakes, ponds, oceans would easily evaporateSlide7

Chapter 17 Section 2

-

Water has a high heat of vaporization

-this is the amount of energy needed to convert 1g of a liquid to gas at the boiling pt.

-difficult to break bonds to vaporize water due to THE STRONG H-BONDS. Because of hydrogen bonding, the heat of vaporization is higher than most other substances.Iron’s heat of vaporization is only 0.447, which means for the same increase in temp as water, Fe only need 0.447

units of

energy.

Water’s

high heat of vaporization (4.184) helps

to moderate daily air temperature around large bodies of waterSlide8

-opposite of

vap

. is known as the heat of condensation (g

→ℓ)

-boiling point of water is high b/c of H- bonding

-it takes more heat to disrupt molecules Slide9

*Read page 480 and write a few sentences describing ice- solid waterSlide10

Chapter 17 Section 3

aqueous solution

- water sample containing dissolved substances

solvent

- dissolving medium, what does the dissolving

*water is known as the universal solventsolute- what is being dissolved

ex-

water and ice tea mixSlide11

solutions are

homogeneous mixtures

-

-the same throughout, uniform in composition, cannot pick out individual pieces

-solute particles in a solution are small

→ ≈1nm

solvation

- process that occurs when a solute dissolves, solute particles become surrounded by solventSlide12
Slide13

-some substances are

insoluble

- not able to be dissolved

-this is b/c their attractions are stronger than water

-Why does oil not dissolve in water?

-because polar molecules only dissolve other polar molecules, nonpolar only dissolve nonpolar-“like dissolves like”Slide14

electrolyte

- conducts an electric current in aqueous solution or the molten state

-ionic compounds are electrolytes

weak electrolyte

- when in solution only a fraction of the solute exists as ions

strong electrolyte- when dissolved almost all of the solute exists as separate ions

nonelectrolyte

- do not conduct an electric current in aqueous or molten stateSlide15

hygroscopic

- salts and other compounds that remove moisture from the air

desiccant

- hygroscopic substances used as drying agents

ex- packets found in shoe boxes, beef jerky

-some compounds are so hygroscopic that they become wet when exposed to moist airdeliquescent compounds

- remove water from air to dissolve completely and form solutions

ex- NaOH