Chapter 3: Water and Life

Question 1

Covalent Bond

Answer 1

Sharing of two electrons between two atoms.

Question 2

Polar bond

Answer 2

A type of bond between two atoms in which electrons are shared unequally. See also “polar molecule.”

Question 3

Electronegativity

Answer 3

More electronegative as one goes up and right on the PTE.

Question 4

Cohesion

Answer 4

Contributes to the transport of water and dissolved nutrients against gravity in plants.

Question 5

Adhesion

Answer 5

Helps counter the downward spiral of gravity.

Question 6

Why water expands when it freezes

Answer 6

The hydrogen bonding tendency gets stronger as the temperature gets lower (because there is less thermal energy to shake the hydrogen bonds out of position). The ice structure is completely hydrogen bound, and these bonds force the crystalline structure to be very “open.”

Question 7

Hydration Shell

Answer 7

The sphere of water molecules around each dissolved ion.

Question 8

Colloid

Answer 8

A stable suspension of fine particles in a liquid

Question 9

Fun Fact

Answer 9

Cotton is a hydrophilic substance but does not dissolve in water, making it a great material for towels.

Question 10

Hydrophobic

Answer 10

Not attracted to water

Question 11

Define “hydration forces”

Answer 11

The forces necessary to dehydrate hydrophilic surfaces (to remove the strongly held layers of water of hydration). Often, this requires substantial work against the cohesive and adhesive forces of water.

Question 12

pH Scale is calculated as…

Answer 12

Negative log (base 10) of the hydrogen ion concentration:
pH = -log[H+]

-log10^(-7) = -(-7) = 7

Question 13

Each pH unit represents a difference of…

Answer 13

10

Question 14

Define a buffer solution

Answer 14

An aqueous solution consisting of a weak mixture of a weak acid and its conjugate base. Blood is a great buffer solution.

Question 15

Ocean acidification

Answer 15

• CO2 mostly responsible
• Ocean pH is .1 lower now than at any other time 420,000 years ago.
• Predictions say that it will drop another .3-.5 pH by the end of the century.

Question 16

Cycle

Answer 16

Emission of CO2
CO2 + H2O -> H2CO3
H2CO3 -> H^+ + HCO3^-
H^+ + CO3^2- -> HCO3^-
CO3^2- + Ca^2+ -> CaCO3

Question 17

Acid Precipitation

Answer 17

Precipitation of 5.2 or lower

Question 18

pOH is _________ proportional to pH

Answer 18

Inversely