Make a list of ten things

that have water in them.

Section 2-2

Interest Grabber continued

DO NOW

• Did either list contain any living things?

DO NOW

• Let’s discuss your list …

• Did your lists contain some of the same things?• Did anything on the other list surprise you?

I. FactsA. 75% of Earth’s surface is water

B. Cells are 70 – 95% water!

C. expands when freezes

1. when in solid format is actually less dense than in liquid state

Properties of Water

II. Water MoleculeA. Molecule is neutral

1. has 10 protons and 10 electrons

B. Water is a polar molecule 1. water is bent - the O molecule is more

negative than the H

2. Therefore water is polar because of the uneven distribution of electrons

btwn the O & H atoms

a. negative pole is near the O atom & positive pole is btwn the H atoms

3. has special properties a. due to ability to form multiple

hydrogen bonds 1 - can be as many as 4 at a time

C. Hydrogen bonds1. Example

a. molecules of water & hydrogen are held together by H-bonds 2. can be attracted to each other

a. due to having both a partial positive & partial negative

3. not as strong compared to ionic or covalent

D. Properties

1. cohesion

a. attraction btwn molecules of the same substance

b. water extremely cohesive

c. water’s cohesion makes the molecules on surface to be drawn inward

1 - reason why water on a smooth surface beads up

2 - also why insects & spiders can walk on water

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Cohesion

• Attraction between molecules of same substance

• b/c of H bonding, H20 extremely cohesive

• Molecules on surface of H20 drawn inward

• Beading effect• Insects can walk on pond’s

surface

2. Adhesion

a. attraction btwn molecules of different substances

b. Example

1- reading water level in graduated cylinder

a - water dips in center b - 2 different molecules (water/glass)

c – adhesion btwn water molecules & glass molecules is stronger than the cohesion btwn water molecules

http://www.visionlearning.com/library/module_viewer.php?mid=57

2 – water rises higher agst the force of gravity in a narrow tube

a – known as capillary action b – a force that draws water out of the

roots of a plant & up the stem & leaves

c – cohesion holds the water together as it rises

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Adhesion

• Attraction between molecules of different substances

• Meniscus in graduated cylinder

• Water climbs slightly up glass, dips in middle

• Rises against force of gravity, aka: capillary action– H20 out of roots into stems

of plant

The water molecule’s charge is ____

1 2 3

33% 33%33%

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1. Positive2. Negative3. Neutral

The water molecule is an example of _______

1 2 3 4

25% 25%25%25%

1. Mixture2. Solution3. Compound4. Suspension

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Cohesive occurs with different molecule substances

1 2

50%50%

1. True 2. False

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Is water cohesive or adhesive?

1 2

50%50%

1. Cohesive2. Adhesive

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When water goes from solid state to a liquid state, molecules ______

1 2 3

33% 33%33%

1. Do nothing2. Expand3. Contract

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Is water polar or nonpolar?

1 2

50%50%

1. Polar 2. Nonpolar

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IV. Solutions & Suspensions

A. water not always pure – often found as a mixture

1. mixture – material composed of two or more

elements or compounds that are physically mixed together but not chemically

a. examples

1 - salt & pepper – mixed but only physically

2 – sugar and sand3 – earth’s atmospheric gases

B.Two types of mixtures can be made with water

1. Solution

a. a homogenous mixture of 2 or more substances

1 – substance breaks away then dissolves

b. parts of a solution1 - Solute – substance being dissolved2 - Solvent – dissolving agent

http://www.northland.cc.mn.us/biology/biology1111/animations/dissolve.html

2.Suspension

a. substance does not dissolve, but breaks into small pieces

b. the movement of water molecules keeps the molecules suspended

1 – mixture of liquid & undissolved material

c. examples

1- your body (blood, mostly water with other cell types)

The water molecule is an example of _______

1 2 3

33% 33%33%

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1. Mixture2. Solution3. Suspension

The atmospheric gases on Earth are an example of _____

1 2

50%50%

1. Mixture2. Solution

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Making kool-aid is an example of ____

1 2

50%50%

1. Mixture 2. Solution

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V. Acids, bases, & pH

A. water can react to form ions

1. ex - forms Hydrogen ions (H+) & Hydroxide ions (OH-)

2. how often?

a. in pure water 1 in every 550 million

B. pH scale

1. used to determine the concentration of H+ in a solution

2. ranges from 0 to 14

a. 7 range is neutral

b. having a pH below 7, makes it more acidic, ‘cause it has more H+

c. having a pH above 7 are called basic, because they have more OH-

Neutral

Incr

easi

ngly

Bas

icIn

crea

sing

ly A

cidi

c

Oven cleaner

Bleach

Ammonia solution

Soap

Sea water

Pure waterHuman blood

MilkNormalrainfall

Acid rainTomato juice

Lemon juice

Stomach acid

3. pure water’s pH scale is 7

4.Strong acids and bases dissociate completely when mixed w/ water

C. Acids

1. forms when H+ ions are in a compound

2. increases H+ conc. (less than 7)

3. strong acids tend to have a pH value btwn 1 – 3 a. example - HCl (stomach acid)

D. Bases

1. forms when the compound has OH- ions

2. reduces H+ conc. (greater than 7)

3. strong bases tend to range from 11 to 14

a. example - NaOH, lye

E. Buffers

1. weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in pH levels

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Acids, Bases & pH

• Buffers help to neutralize the acid or base

• Examples?– Tums, Rolaids

2. Internal pH of most cells is about 7

a. if changes will affect the chemical reactions that take place there

b. changes in pH can be harmful to cells

c. important to maintaining homeostasis

d. Buffers – minimize changes in concentrations of H+ and OH- in a solution – so cells adjust slowly

Stomach acid is very acidic

1 2

50%50%

1. True2. False

Buffers are needed to make an acidic a basic

1 2

50%50%

1. True2. False

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Is bleach acidic, neutral or basic?

1 2 3

33% 33%33%

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1. Acidic2. Neutral 3. Basic

Is water acidic, neutral or basic?

1 2 3

33% 33%33%

1. Acidic2. Neutral 3. Basic

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