Properties of Water

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Which is ice and which is water?

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Water is Less Dense as a Solid

Water

Ice

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Homeostasis

Ability to maintain a steady state despite changing conditions

Water is important to this process because:

a. Makes a good insulator

b. Resists temperature change

c. Universal solvent

d. Coolant

e. Ice protects against temperature extremes (insulates frozen lakes)

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Solutions & Suspensions

Water is usually part of a mixture.

There are two types of mixtures:

Solutions

Suspensions

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Solution

Ionic compounds disperse as ions in water

Evenly distributed

SOLUTE

Substance that is being dissolved

SOLVENT

Substance into which the solute dissolves

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Solution

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Suspensions

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

Water keeps the pieces suspended so they don’t settle out.

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Acids, Bases and pH

One water molecule in 550 million naturally dissociates into a Hydrogen Ion (H+) and a Hydroxide Ion (OH-)

Hydrogen Ion Hydroxide Ion

Acid Base

H2O  H+ + OH-

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The pH Scale

Indicates the concentration of H+ ions

Ranges from 0 – 14

pH of 7 is neutral

pH 0 up to 7 is acid … H+

pH above 7 – 14 is basic… OH-

Each pH unit represents a factor of 10X change in concentration

pH 3 is 10 x 10 x 10 (1000) stronger than a pH of 6

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Acids

Strong Acids have a pH of 1-3

Produce lots of H+ ions

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Bases

Strong Bases have a pH of 11 to 14

Contain lots of OH-ions and fewer H+ ions

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Buffers

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

Produced naturally by the body to maintain homeostasis

Weak Acid

Weak Base

Slide 35