(Unit 1) Chapter 3: Water and the Fitness of the Environment Flashcards
What is the biological medium here on Earth?
Water
_____-________ of Earth’s surface is submerged in _____
Three-quarters
Water
The _______ distribution of electrons makes water a _____ molecule
Unequal
Polar
Who highlights the importance of water to life? Where?
Lawrence Henderson
In a book: The Fitness of the Environment
In water, the slightly ________ hydrogen is attracted to the slightly ________ oxygen of a nearby molecule
Positive
Negative
What are molecules of water held together by?
Hydrogen bonds
True or False:
When water is in liquid form, the hydrogen bonds are very strong
False, the hydrogen bonds are very fragile each about 1/20 as strong as a covalent bond
What is the phenomenon called when hydrogen bonds hold water together?
Cohesion
Define:
Adhesion
Clinging of one substance to another
Define:
Surface tension
A measure of how difficult it is to stretch or break the surface of a liquid
True or False:
Water has greater surface tension than most other liquids
True
Define:
Kinetic energy
The energy of motion, anything that moves has kinetic energy
True or False:
Heat is a form of energy
True
Define:
Temperature
A measure of heat intensity that represents the average kinetic energy of the molecules, regardless of volume
For a given body of matter, the amount of ____ is a measure of the matter’s total _______ energy due to motion of its _________
Heat
Kinetic
Molecules
If the amount of heat is a measure of the matter’s total kinetic energy, what does the heat depend on?
Depends in part on the matter’s volume
In what temperature scale does water freeze at 0 degrees and boil at 100 degrees at sea level?
Celsius Scale
What is a calorie?
A unit of heat
Define:
1 cal
The amount of heat it takes to raise the temperature of 1 g of water by 1 degrees Celsius (or the the amount of heat 1 g of water releases when cooled by 1 degrees Celsius)
What does kcal represent?
Kilocalories
Define:
1 kcal
The amount of heat needed to raise 1 kg of water by 1 degrees Celsius
What is a joule?
An energy unit
Convert joule to calories and calorie to joules
1 J = 0.239 cal
1 cal = 4.184 J
Define:
Specific heat
The amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1 degrees Celsius
State the specific heat of water
1 cal/g/degrees Celsius
The transformation from a liquid to a gas is called:
Vaporization or evaporation
Define:
Heat of vaporization
The quantity of heat a liquid must absorb for 1 g of it to be converted from the liquid to the gaseous state
True or False:
Water has a high specific heat but a low heat of vaporization
False, for the same reason that water has a high specific heat, it also has a high heat of vaporization relative to most other liquids
The cooling of the surface of the liquid that remains behind after evaporation is known as:
Evaporative cooling
What effect does the high amount of energy required to vaporize water have?
Helps moderate Earth’s climate
What effect does the evaporative cooling of water have?
Contributes to the stability of temperature in lakes and ponds and provides a mechanism that prevents terrestrial organisms from overheating
Define:
Solution
A liquid that is a completely homogeneous mixture of two or more substances
Define:
Solvent
The dissolving agent of a solution
Define:
Solute
The substance that is dissolved in a solution
Define:
Aqueous solution
A solution which water is the solvent
Define:
Hydration shell
The sphere of water molecules around each dissolved ion
True or False:
Compounds have to be ionic to dissolve in water
False, compounds do not have to be ionic to dissolve in water (e.x. sugar)
Explain what water molecules do to a table salt molecule (2)
The oxygen region of water attracts to the positively charged ion (sodium), forming a hydration shell
The hydrogen region of water attract to the negatively charged ion (chlorine), forming another hydration shell
Any substance that has an affinity for water is said to be:
Hydrophilic
Define:
Colloid
A stable suspension of fine particles in a liquid
When a substance is hydrophobic, what properties does it have? (2)
Non-ionic, non-polar (or some other reason cannot form hydrogen bonds)
Seem to repel water
Define:
Molecular Mass
The sum of the masses of all the atoms in a molecule
Biological chemistry is “___” chemistry
Wet
What does a mole represent?
An exact number of objects (6.02 * 10^23)
What is the number of objects in a mole known as?
Avogradro’s number
How many daltons are in 1 gram?
6.02 * 10^23 (Avogadro’s Constant)
Define:
Molarity
The number of moles of solute per liter of solution
If sucrose has a molecular mass of 342 daltons, how grams does 1 mol of sucrose weigh?
342 grams
What is a hydrogen ion?
A single proton with a charge of +1
What is a hydroxide ion?
An oxygen and hydrogen ion with a charge of -1
Occasionally, the hydrogen atom participating in a hydrogen bond between two water molecules shifts from on molecule to the other. Explain this reaction
Originally, 2 water molecules are attracted via a hydrogen bond
Now, the hydrogen ion (proton) of one water molecule binds to the other water molecule to form a hydronium ion (H3O+), leaving a hydroxide ion (OH-)
Define:
Acid
A substance that increases the hydrogen ion concentration of a solution
Define:
Base
A substance that reduces the hydrogen ion concentration of a solution
True or False:
The conversion of water to hydronium and hydroxide ions is a reversible reaction
True
What do biologists use to describe how acidic or basic something is?
pH scale
True or False:
The dissociation of water is common and can change the acidity of the water
False, the dissociation of water is statistically rare and only adding certain kinds of solutes can change how acidic/basic the water is
How do acids increase the hydrogen ion concentration of a solution?
When acids dissolve in water, they donate additional H+ to the solution
How do bases reduce the hydrogen ion concentration of a solution? (2)
Some accept hydrogen ions (e.x. Ammonia)
Some dissociate, forming hydroxide ions that combine with hydrogen ions to form water (e.x. Sodium hydroxide)
What is the difference between a strong base/acid and a weak base/acid?
Strong base/acid dissociates completely when mixed with water
Weak base/acid reactions with water is reversible (e.x. Ammonia can accept H+ and then release H+)
In any aqueous solution at __ degrees Celsius, the product of the __ and ___ concentrations is constant at __^___. This can be written as:
25 H+ OH- 10^-14 [H+][OH-] = 10^-14
What is the pH of a solution defined as?
The negative logarithm (base 10) of the hydrogen ion concentration
As pH increases, H+ concentration ________
Declines
If the solution of a pH is 10, what is the concentration of the hydroxide ions?
10^-4 M
In molarity, what is how is a 1 mol/L solution indicated?
1 M solution
Define:
Buffers
Substances that minimize changes in the concentrations of H+ and OH- in a solution
What is an example of a buffer? State the reaction that this buffer undergoes
Carbonic acid (H2CO3), formed when CO2 reacts with water in blood plasma)
When H+ concentration in blood falls, the carbonic acid dissociates to replenish hydrogen ions
When H+ concentration in blood rises, the bicarbonate combines with the H+ to form carbonic acid again
Define:
Acid precipitation
Rain, snow, or fog with a pH lower (more acidic) than pH 5.2
What is the pH of uncontaminated rain around?
5.6
Define:
Calcification
The production of calcium carbonate (CaCO3) by corals and other organisms
What is the calcification in corals and such related to?
The levels of CO3(2-) in the water
When CO2 dissolves in seawater, it reacts with water to form what?
Carbonic acid
Almost all carbonic acid in seawater dissociates into what two ions?
Bicarbonate (HCO3-) and Carbonate (CO3(2-))
