Biology Ch3

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1

Why are water molecules are polar?

Water molecules are polar because the electrons of the polar covalent bond spend more time by the oxygen than the hydrogen. They are also unevenly distributed. Polarity allows water molecules to form hydrogen bonds with each other.

The water molecule is polar because the shared electrons are closer to the oxygen atom rather than the hydrogen atoms.

2

Why are water molecules capable of hydrogen bonding with 4 neighboring water molecules?

The oxygen atom is charged as 2- .And the two hydrogen atoms are charged as 1+ each.Therefore the oxygen atom can attract two hydrogen atoms of other two water molecules and the two hydrogen atoms can attrat two oxygen atoms of another two water molecules

3

Four characteristics of water that are emergent properties resulting from hydrogen bonding.

1. Cohesive Behavior

2. Ability to moderate temperature,

3.Expension upon freezing,Denser as a liquid than as a solid. 4.Versatility as a solvent,Able to absorb large amounts of energy

4

Cohension

Water is attracted to other water. This is cohesion

5

How water's cohesion and adhesion contribute to the movement of water from roots to the leaves of a tree?

The cohesion of water allows a long string of water molecules to be hydrogen bonded to all the way from the roots to the leaves in a long train of water molecules. Adhesion helps this process with capillary action, where the water that is attracted to the side of the of the xylem vessels, which allows other water molecules to move further up. Finally, transpiration acts as a water "pump" against gravity, by having water molecules evaporate out through the stomata on the leaves of plants, and this evaporation action pulls the chain of water molecules up behind it.

6

Adhesion

Attraction between different substances, for example, between water and a plant cell walls.

Water is attracted to other materials besides water. This is adhesion

7

Heat

Heat is an extensive property, measured in BTU's. it is the amount of heat energy required to increase the temperature of 1 pound of water from 3.8 degrees to 4.4 degrees Celsius.

8

Temperature

Temperature is an intensive property, measured in degrees, while heat is an extensive property measured in BTU's. An intensive property is not dependent on the amount of substance present -- water boils at a temperature of 100 degrees, whether it's a gallon or a million gallons.

9

Explain the following observations by referring to the properties of water:
? Coastal areas have milder climates than adjacent inland areas.

Water is able to absorb large amounts of energy, including heat. So the ocean absorbs heat in the summer because the water is cooler than the air, sucking the heat out of the air, thus cooling the air in summer. In the winter, the air is cooler than water, so the heat moves from the water to the air, warming the air in winter.

10

Explain the following observations by referring to the properties of water:
Ocean temperatures fluctuate much less than temperatures on land.

Water is able to absorb large amounts of energy, including heat, and is denser as a liquid than a solid. Therefore, it takes a lot of energy to heat water, and water does not give up it's heat as quickly as air does -- high specific heat and high heat of vaporization

11

Insects like water striders can walk on the surface of a pond without breaking
the surface.

The cohesive property of water -- the tendency of water to be attracted to water, makes the top layer of water molecules that don't have any water above them are pulled inward to other molecules, so when a water strider steps on water, the force of the top layer of water coheres to itself and resists the foot of the water strider from separating water molecules from each other.

12

If you slightly overfill a water glass, the water will form a convex surface above the top of the glass.

The cohesive property of water -- the water at the top of the overfilled glass is more attracted to the the water than to the side of the glass, creating a convex meniscus

13

Humans sweat and dogs pant to cool themselves on hot day

High specific heat Water absorbs latent heat in order to evaporate, and this absorption of heat causes a cooling for sweating humans and panting dogs.

14

Ice floats on water

Water expands as it changes from a liquid to a solid, becoming less dense rather than more dense

15

Solute

Substance that is dissolved

16

Solvent

dissolving agent of a solution

water

17

Solution

is a liquid that is a completely homogeneous mixture of substance

18

hydrophobic

Hates water, substance is one that does not have an affinity for water

oils, nonpolar bond

19

Hydrophilic

Loves water, substance is one that has an affinity for water

20

Explain how you would make up a one molar (1M) solution of ethyl alcohol.C2H6O.

2 carbons - 24 grams, 6 hydrogens, 6 grams, 1 oxygen, 14 grams, 24 + 14 + 6 = ethanol has a molar weight of 44. Ethanol is 0.789 grams per milliliter, so 55.8 milliliters of ethanol in 1 liter of water will create a 1 molar solution of ethanol.

21

If you place a paper towel so that it touches spilled water, the towel will draw
in the water.

Adhesion

22

Name the products of the dissociation of water and give their concentration in
pure water.

2 H2O OH? + H3O+
H3O^+1 = hydronium ion
OH^-1 = hydroxide ion
Concentration in pure water 1x10^-7 mol/L

23

Define acid

A solution in which the concentration of hydronium ions is greater than 10^-7 moles per liter. pH less then 7

24

Define a base

A solution in which the concentration of hydronium atoms is less than 10^-7 moles per liter. greater the 7

25

Define pH

the measure of concentration and activity of hydronium atoms in a solution. range of 6-8

26

Explain how acids and bases may directly or indirectly alter the hydrogen ion
concentration of a solution

When an acid interacts with a solution, it can donate protons. When an alkaline interacts with a solution, it can accept protons.

27

Define specific heat

The specific heat is the amount of heat per unit mass required to raise the temperature by one degree Celsius.

28

What is a buffer? In your explanation, use as a model acetic acid and acetate in
solution

Acetic acid and acetate maintain a pH equilibrium. Acetic acid is an acid and acetate is a base. The two function together as a buffering system.
CH3COOH <==> CH3COO- + H2 When the concentration of protons increases slightly, the protons react with acetate ions to form acetic acid and pH does not change. If the concentration of protons decreases slightly, acetic acid gives up protons and pH stays the same

29

Define heat of vaporization

Heat of Vaporization-the amount of heat required to convert unit mass of a liquid into the vapor without a change in temperature.

30

Explain how the burning of fossil fuel may affect

Acid precipitation by a chemical reaction that begins when compounds like sulfur dioxide and nitrogen oxides are released into the air. These substances can rise very high into the atmosphere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as acid rain.

31

Explain how the burning of fossil fuel may affect

ocean acidification is the ongoing decrease in the pH of the Earth's oceans, caused by the uptake of carbon dioxide (CO2) from the atmosphere. An estimated 30?40% of the carbon dioxide released by humans into the atmosphere dissolves into oceans, rivers and lakes.


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