Chapter 3: Water and Life

Define polar molecule

A molecule with an uneven distribution of charges in different regions of the molecule

Why is water considered polar?

Overall charge unevenly distributed

Explain hydrogen bonding in terms of water. How many hydrogen bonds can a single water molecule form?

Positive hydrogen of one molecule attracted to negative oxygen of nearby molecule. Water can form four bonds.

Cohesion

Linking together of like molecules with hydrogen bonds.

Ex. Water drops on penny

Adhesion

Clinging of one substance to another.

Ex. Water in a plant cell or the lizard walking on water

Calorie

Amount of heat energy required to raise temperature of 1g of water by 1 degree Celsius. Also amount of heat energy that 1g of water cools by 1 degree Celsius

Specific Heat

Amount of heat absorbed or lost for 1g o that substance to change its temp by 1 degree Celsius. Water has a HIGH specific heat.

How does hydrogen bonding contribute to water's high specific heat?

heat breaks the hydrogen bonds before raising temperatures of water

How does Water's high specific heat contribute tot he moderation of temperature. How is this property important to life?

Water may cool air at night and warm during the day. High specific heat stabilizes ocean temperatures. This is important to life because organisms made of water are able to resist changes in their own temperature. Keeps life in balance.

Evaporation

Process by which a liquid changes to gas

Define Heat of Vaporization. Explain at least three effects of this property on living organisms

Heat of Vaporization-- quantity of heat a liquid must absorb for 1g of it to be converted from the liquid to the gaseous state.

1. moderate earth's climate

2. severity of steam burns on skin

3. sweat in humans

What would happen to organisms if ice froze at the bottom?

Everything would freeze. Ice frozen on top allows life underneath to survive

Why does ice float? Why is 4 degrees Celsius a critical temperature?

Ice is less dense than water. Less than 4 degrees Celsius water begins to freeze because more of its molecules move too slow to break hydrogen bonds

Solvent

dissolving agent of a solution

WATER IS THE UNIVERSAL SOLVENT

Solution

A liquid that is completely homogenous mixture of 2 or more substances

Solute

Substance that is dissolved

Why is water such a fine solvent?

Most substances dissolve in ater. No need for ionic for ionic compounds

Hydrophobic

No affinity for water (vegetable oil)

water fearing...

Hydrophillic

h2o loving (cotton)

Molarity

Number of moles of solute per liter of solution. Unit of concentration used for aqueous solutions

What two ions form when water dissociates?

hydronium ion hydroxide ion

What is the concentration of each ion in pure water at 25 degrees celsius?

10-7 M

What has a pH of 7 pH is defined as the negative log of the hydrogen ion concentration [H+]. How is water assigned a pH of 7?

Maintains equillibrium

Acid

Substance that increases hydrogen ion concentration of a solution

Base

Substance that reduces hydrogen ion concentration of a solution with higher concentration of OH- than H+ solution

How can buffers moderate pH changes?

Minimizes changes in concentration of H+ OH- in a solution. Accepts hydrogen ions from the solution when they are in excess and bonding hydrogen ions to solution

Give two reasons precipitation is more acidic today than compared to 1900

1. Burning of fossil fuels

2. Ocean acidification

What products of fossil fuel burning contribute to acid precipitation?

Carbon dioxide

Discuss how CO2 emissions affect marine life and ecosystems

Lowers pH. Reduces carbonate concentration. Required for calcification the production of calcium carbonate which helps build reefs.