Test 1 Intro to Bio + Water

Question 1

props of water

Answer 1

Polar molecule
Cohesion and adhesion
High specific heat
Density – greatest at 4C
excellent solvent of life

Question 2

bonds within water molecules

Answer 2

hydrogen and oxygen in water molecule are bonded with covalent bonds

Question 3

polarity of water

Answer 3

Within a water molecule, the bonds between oxygen and hydrogen are highly polar.
Water’s oxygen atom attracts electrons more forcefully than either of its hydrogen atoms, electrons are denser around the oxygen atom, which becomes somewhat negative charge
molecules that contain an unequal charge distribution, possess distinct positive and negative regions, or pole
Partial electrical charges develop:
- oxygen is partially negative
- hydrogen is partially positive

Question 4

non polar molecules

Answer 4

lack regions of electric charge
electrons are evenly distributed

Question 5

Hydrophilic

Answer 5

Polar molecules are hydrophilic, or “water loving”, attracted to water molecules and dissolve easily in water

Question 6

hydrophobic

Answer 6

Nonpolar molecules are hydrophobic, or “water fearing”, repelled by water molecules and do not dissolve in water

Question 7

hydrogen bonds

Answer 7

weak attractions between the partially negative oxygen of one water molecule and the partially positive hydrogen of a different water molecule.

Each water molecule
can form hydrogen
bonds with up to
four neighbors.

They form, break, and reform with great frequency

Question 8

water chemistry

Answer 8

The polarity of water causes it to be cohesive and adhesive.
Polarity unequal charge distribution in a molecule resulting in a – region and a + region

Question 9

cohesion

Answer 9

water molecules stick to other water molecules through hydrogen bonding

Question 10

adhesion

Answer 10

water molecules stick to other polar molecules by hydrogen bonding, the prop of water molecules to cling to any hydrophilic substance

Question 11

organisms depend on cohesion

Answer 11

Cohesion & adhesion are responsible for the transport of the water column in plants against the pull of gravity

Capillary action – cohesion & adhesion working together to draw water up the veins of plants
Capillary action - substances having a hyrophilic surface, attraccting water molecules with enough force to overcome the pull of gravity, powered by adhesion

Related to plants ability to get water from their roots to the treetops
Capillary action brings water part of the way up, and adhesion and cohesion help to bring it the rest of the wy through the tree

Question 12

surface tension

Answer 12

a measure of the force necessary to stretch or break the surface of a liquid, is related to cohesion.
Cohesion between molecules creates a film or layer that resists being separated, this property is called surface tension, permits things that are too dense to float to sometimes walk across the surface of water if they don’t disturb this layer
Water has a greater surface tension than most other liquids because hydrogen bonds among surface water molecules resist stretching or breaking the surface.

Question 13

water moderates temperature on Earth

Answer 13

It takes more heat to raise the temp of some substances than it does to raise the temp of others
(Specific Heat dependent)
When water is heated, its individual molecule cannot move faster until hydrogen bonds are broken, therefore water has a high specific heat, absorbs considerable heat before its temp raises markedly

Water stabilizes air temperatures by absorbing heat from warmer air and releasing heat to cooler air.
Water can absorb or release relatively large amounts of heat with only a slight change in its own temperature.

Prevention of temperature fluctuations that are outside the range suitable for life.
Coastal areas having a mild climate
A stable marine environment

Question 14

specific heat

Answer 14

xthe amount of heat that must be absorbed or lost for one gram of a substance to change its temperature by 1oC.

Question 15

evaporative cooling

Answer 15

The cooling of a surface occurs when the liquid evaporates
Water is an efficient cooling agent, b/c all hydrogen bonds must be broken water can’t change from liquid to gas until it is heated at very high temp
When water evaporates it takes with it much of of the heat it absorbed, evaporation can cool an organism or surface
This is responsible for:
Moderating earth’s climate
Stabilizes dentemperature in aquatic ecosystems
Preventing organisms from overheating

Question 16

density of water

Answer 16

Most dense at 4oC
Contracts until 4oC
Expands from 4oC to 0oC
density of water:
Prevents water from freezing from the bottom up.
Ice forms on the surface first—the freezing of the water releases heat to the water below creating insulation.
When water reaches 0C, hydrogen bonds crystallize and lock in place, leaving more space between them (gets less dense)
Ice is about 10% less dense than water at 4oC.

Question 17

dissolving in water

Answer 17

Polar substances dissolve other polar substances
Sugar and other substances that dissolve in water are polar
fats , oils, and waxes separate from water when they are mixed together b/c water is polar and oils are nonpolar and there is no attraction between them

Question 18

Capillary action

Answer 18

Capillary action – cohesion & adhesion working together to draw water up the veins of plants
Capillary action - substances having a hyrophilic surface, attraccting water molecules with enough force to overcome the pull of gravity, powered by adhesion