Water & pH Packet #7 Chapter #2. Introduction Most abundant liquid in the world Makes up at least half of all living organisms and up to 95% of some species

Water & pHPacket #7

Chapter #2

Introduction

Most abundant liquid in the world

Makes up at least half of all living organisms and up to 95% of some species.

75% of earth is submerged in water

Naturally occurring water consists of 99.76% H2O

Wednesday, April 19, 2023

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The Water Molecule


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Properties of WaterDensity

Density


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Water has a maximum density at 4ºC This is when water is in a liquid

state The density will be 1.

H2O (l) is more dense than H2O (s)

Water freezes from top downward allowing ice to form at the top

Ice at top can insulate the warmer water below that layer from colder temperatures above

Prevents large bodies of water from freezing solid and allowing the survival of aquatic organisms

Properties of WaterCohesion and Adhesion

Cohesion & Adhesion

Cohesion Attraction of molecules

of the same substance. The hydrogen bonding

allows water to be cohesive

Causes individual water molecules on the top to be drawn inward allowing for the appearance a smooth surface.

Cohesion & Adhesion

Adhesion Attraction of molecules

of different substances. Example of water in a

graduated cylinder.

HW Assignment Define capillary action

and relate it to the concept of adhesion.

Properties of WaterSpecific Heat

Specific Heat

Specific heat is defined as the amount of heat, measured in calories, required to raise the temperature of one gram of a substance by one Celsius degree.

Water has a very high specific heat It takes a long time for

water to heat up.

Properties of Water

Solubility & Water

Solubility

Water is a versatile solvent due to its polarity

Can form an aqueous solution.


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Definitions

Mixture A portion of matter that

can be separated into two or more substances by physical means alone

Substance composed of 2 or more elements or compounds that are mixed together, but are not chemically combined The two substances

can be separated Salt and pepper Sugar and sand


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Definitions II

Solution A homogeneous (of

uniform structure or composition throughout ) mixture of two or more substances, which may be solids, liquids, gases, or a combination of these.

Homogenous mixture Sugar in water (Sugar-

water) One component (Major),

of a solution, is found in a greater amount Solvent

One component (Minor), of a solution, is found in a lesser amount Solute


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16The different regions of the polar water molecule can interact with ionic compounds called solutes and dissolve them

Negative

oxygen regions

of polar water

molecules are

attracted to sodium

cations (Na+).

+

+

+

+Cl –

–

–

–

–

Na+

Positive hydrogen regions

of water molecules cling to chloride

anions (Cl–).

++

+

+

–

–

–

–

–

–Na+

Cl–

Figure 3.6

Solubility

“Likes dissolves likes” Polar with polar Non-polar with non-polar

Oil and water are dislikes Water = polar Oil = non-polar

We say that oil and water are nearly completely immiscible The oil is

suspended


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Other Important Points II

Hydrophilic substanceWater lovingHas an affinity for

water

Hydrophobic substanceWater hatingDoes not have an

affinity for water


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pH

pH

The pH scale will tell us how willing a compound is in giving hydrogen ions (H+)

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pH—Acid & Base Reaction

Bronsted-Lowry Acid A substance that donates a

hydrogen ion (H+) An acidic solution has a

higher concentration of H+ than pure water and have pH values below 7

Bronsted-Lowry Base A substance that accepts a

hydrogen ion (H+) A basic, or alkaline

solution, contain lower concentrations of H+ than pure water and have pH values above 7.

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pH Scale

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Review

Review

Documents

Water & pH Packet #7 Chapter #2. Introduction Most abundant liquid in the world Makes up at least half of all living organisms and up to 95% of some species