AP Bio: Chapter 3 water and life
Consider coffee to which of added sugar. Which of these is the solvent? Which of these is the solute?
Solvent- coffee Solute- sugar
Which property explains the ability of a water strider to walk on water?
Surface tension
Specific heat
The amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1°C
Exercise will result in the production of CO2, which will acidify the blood. Explain the buffering system that minimizes blood pH changes
The chemical equilibrium between carbonic acid and bicarbonate acts as a pH regulator
Adhesion
The clinging of one substance to another
Molarity
The number of moles of a solute per liter of solution
Cohesion
The phenomenon of the collective hydrogen bonds holding water together
Heat of vaporization
The quantity of heat a liquid must absorb for 1 g of it to be converted from the liquid to gaseous state
What is water's specific heat? Is it high or low?
The specific heat of water is: 1cal/g * 1°C This is a high specific heat
Solute
The substance being dissolved
Water has a pH of 7 PH is defined as the negative log of the hydrogen ion concentration.
Therefore water is assigned a pH of seven because the log of 10 to the -7th power is 7
Solution
They liquid that is completely homogeneous. It is a mixture of two or more substances
Evaporation
Transformation of a liquid to a gas
Explain why water is the universal solvent
Water can dissolve ionic compounds, many compounds made up of non-ionic polar molecules, as well as molecules such as proteins
How does water's specific heat compare to alcohol's specific heat?
Water: 1 cal/g Alcohol: .6 cal/g
How does hydrogen bonding contribute to Waters high specific heat?
When the temperature of water slightly drops, many additional hydrogen bonds form releasing a considerable amount of energy in the form of heat
Summarize how waters high specific heat contributes to the moderation of temperature. How does this property important to life?
With a high specific heat, a large body of water can absorb and store a huge amount of heat from the sun during the daytime. As it cools during the night, it warms the air. This is important to life because some organisms live in the pond water, while others rely on it for water. If the temperature was not right, life would not thrive.
Because the pH scale is logarithmic, each numerical change represents a 10X change in ion concentration a) how many times more acidic is a pH of 3 compared to a pH 5 b) how many times more basic is a pH of 12 compared to a pH of 8 c) explain the difference between a pH of 8 and a pH of 12 in terms of H+ concentration
a) 5-3=2 10^2 = 100 b) 12-8=4 10^4= 10000 c) 12-8=4 10^4 times greater
Solvent
the dissolving agent
Give two reasons precipitation is more acidic today compared to 1900
1. The burning of wood and fossil fuel's creating harmful gases 2. The burning and destruction of vast areas of forest
Explain 3 effects of heat of vaporization and evaporation on living organisms
1. Water evaporates from plant leaves helping the leaves from becoming too warm in the sunlight 2. Evaporation of sweat from human skin dissipates heat 3. Heat of vaporization accounts for the severity of steam burns
What is the concentration of each ion in pure water at 25°C ?
10^-7 M at 25°C
Surface tension
A property related to cohesion. It is a measure of how difficult it is to stretch or break the surface of a liquid. Water's surface tension is greater than most other liquids
Acid
A substance that increases the hydrogen ion concentration of a solution
Base
A substance that reduces the hydrogen ion concentration of a solution
Calorie
A unit of heat. It is the amount of heat it takes to raise the temperature of 1 g of water by 1°C
Acid precipitation is increasing. What is the pH of uncontaminated rain?
About 5.6
Which property is demonstrated when you see beads of water on a waxed car hood?
Adhesion; the water molecules cling to one another forming beads
Hydrophilic
Any substance that attracts/absorbs water
Hydrophobic
Any substance that repels water
How do buffers moderate pH change?
By excepting hydrogen ions when they are in excess and donating hydrogen ions to the solution when they have been depleted
How do CO2 emissions affect marine life and ecosystems?
CO2 dissolves in the sea water creating carbonic acid, lowering the pH, causing acidification
Explain hydrogen bonding. How many hydrogen bonds can a single water molecule form?
Hydrogen bonding occurs when the slightly positive hydrogen molecule bonds with a slightly negative oxygen molecule nearby
What two ions form when water dissociates?
Hydronium (H3O+) and hydroxide (OH-)
Give an example of something that is hydrophilic and hydrophobic
Hydrophilic - cotton hydrophobic - vegetable oil
Why does ice float? Why is 4°C the critical temperature?
Ice floats because it has a lower density than water in the liquid state. It has a lower density because of the separation between the molecules. As a result of hydrogen bonding, water expands when it solidifies so below 4°C, water begins to freeze
Ice floats, so what? Consider what would happen if ponds and other bodies of water accumulated ice at the bottom. Describe why the property of ice floating is important
If I sake, eventually all bodies of water would freeze solid and only a few inches at the top with the law during the summer. Because ice floats, the upper frozen layer insulates the liquid water below keeping it from freezing. When summer comes the only layer to thaw is the top layer in the pond is restored to the liquid state of water
Why does oil float on top of water? Explain this property in terms of hydrogen bonding
Oil behaves hydrophobically and water. The Oil molecules cannot form hydrogen bonds with the water
