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Water and the Fitness of the Environment. What molecule supports all of life ?. Transport over land. Solar energy. Net movement of water vapor by wind. Precipitation over land. Precipitation over ocean. Evaporation from ocean. Evapotranspiration from land. Water Cycle. Percolation

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water cycle

Transport

over land

Solar energy

Net movement of

water vapor by wind

Precipitation

over land

Precipitation

over ocean

Evaporation

from ocean

Evapotranspiration

from land

Water Cycle

Percolation

through

soil

Runoff and

groundwater

how does the polarity of water affect its properties
How does the polarity of water affect its properties?
  • What is a polar molecule?
    • Has polar bonds
    • Water has polar covalent bonds
      • Oxygen is more electronegative than H
      • Electrons of covalent bonds spend more time closer to Oxygen than to H
      • Creates a polar molecule
        • O region is partially negative
        • H regions are partially positive
      • Causes the anomalous properties of water
polar molecule

–

O

POLAR MOLECULE

H

H

+

+

H2O

hydrogen bonds

–

+

Water

(H2O)

+

Hydrogen bond

–

HYDROGEN BONDS

Ammonia

(NH3)

+

+

+

how does this change when water is in different states
How does this change when water is in different states?
  • Slightly positive H of 1 molecule is attracted to slightly negative O of nearby molecule creating a H bond that holds those molecules together
    • Hydrogen bonds by themselves are not that strong; however, when they are continuously forming, re-forming, breaking, then at any instant a large percentage of water molecules are hydrogen-bonded to neighbors
what are the 4 emergent properties of water
What are the 4 Emergent Properties of Water?
  • Cohesive behavior
  • Ability to moderate temperature
  • Expansion up freezing
  • Versatility as a solvent
what are the 4 emergent properties of water cohesive behavior
What are the 4 Emergent Properties of Water?Cohesive Behavior
  • What is cohesion?
      • Molecules are linked by multiple hydrogen bonds which make water more structured than other liquids
      • Collectively, hydrogen bonds hold substance together = Cohesion
what are the 4 emergent properties of water cohesive behavior1
What are the 4 Emergent Properties of Water?Cohesive Behavior
  • Contributes to transport of water and dissolved nutrients against gravity in plants
    • There exists a network of water-conducting cells help water reach the leaves from the roots

What starts the process?

what are the 4 emergent properties of water cohesive behavior2
What are the 4 Emergent Properties of Water?Cohesive Behavior
  • Cohesion is supported by Adhesion
  • What is Adhesion?
      • clinging of one substance to another
        • Adhesion of water to cell walls by those same hydrogen bonds
what are the 4 emergent properties of water cohesive behavior3
What are the 4 Emergent Properties of Water?Cohesive Behavior
  • How is this related to Surface Tension?
    • Surface tension= how difficult it is to stretch or break the surface of a liquid
what are the 4 emergent properties of water cohesive behavior4
What are the 4 Emergent Properties of Water?Cohesive Behavior
  • Benefits:
          • Bugs that walk on water
          • Bugs that use air bubble to breath underwater
          • Leads to transport of water and its dissolved nutrients against gravity in plants
          • Water molecules leaving tree through evaporation cause its H bonds to tug on water molecules in the tree creating an upward force of water
what are the 4 emergent properties of water ability to moderate temperature
What are the 4 Emergent Properties of Water?Ability to Moderate Temperature
  • How does water moderate air temperature?
    • By absorbing heat from the air that is warmer and releasing stored heat to air that is cooler
    • Can absorb or release a large amount of heat with only slight change in its own temperature
what are the 4 emergent properties of water ability to moderate temperature1
What are the 4 Emergent Properties of Water?Ability to Moderate Temperature
  • How does this work?

1st - Have to understand what heat is:

      • Heat is a form of energy
      • Measure of the amount of heat is a measure of the matter’s TOTAL kinetic energy due to motion of its molecules and depends on matter’s volume
        • The energy of motion= kinetic energy
      • Related to temperature, but not same
        • Temperature= measure of heat intensity that represents the average kinetic energy of the molecules, regardless of volume
what are the 4 emergent properties of water ability to moderate temperature2
What are the 4 Emergent Properties of Water?Ability to Moderate Temperature
  • How does this work?
    • Water stabilizes temperatures from its relatively high specific heat
  • Specific Heat-
    • is defined as the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1 °C
        • For Water- 1 calorie per gram per °C = 1 cal/g/°C
        • Because has high specific heat relative to other material, water will change its temperature less when it absorbs or loses a given amount of heat
what are the 4 emergent properties of water ability to moderate temperature3
What are the 4 Emergent Properties of Water?Ability to Moderate Temperature
  • How does this work?
      • In order to absorb heat, bonds must be broken
      • Because once one bond is broken, it can reform with another molecule, the heat absorbed is lost through the reforming of bonds,
      • Much of the actual heat absorbed is used to break the bonds before the molecules can begin moving faster
      • Water has a high specific heat and high heat of vaporization
what are the 4 emergent properties of water ability to moderate temperature4
What are the 4 Emergent Properties of Water?Ability to Moderate Temperature
  • What is Evaporative cooling?
      • Molecules moving fast enough to overcome the attraction to each other, can leave the liquid and enter the air as gas
        • Called Vaporization orEvaporation
      • Heat of vaporization
        • Quantity of heat a liquid must absorb for 1 g of it to be converted from liquid to the gaseous state
        • High specific heat= high heat of vaporization
        • Caused by the H bond
what are the 4 emergent properties of water ability to moderate temperature5
What are the 4 Emergent Properties of Water?Ability to Moderate Temperature
  • What is Evaporative cooling?
        • As liquid evaporates, the surface of the liquid that remains behind cools down
        • Occurs because the “hottest” molecules with greatest kinetic energy, are the most likely to leave as a gas
what are the 4 emergent properties of water ability to moderate temperature6
What are the 4 Emergent Properties of Water?Ability to Moderate Temperature
  • Benefits:
    • Bodies of water maintain a constant temperature keeping its inhabitants from going into heat shock on a hot day
    • Keeps water warm on a cool day and cool on a hot day, and in turn, cools the air around it on a hot day and heats air around it on a cool day
    • Keeps temp for fluctuating greatly due to the fact that oceans cover the earth
    • Helps moderate Earth’s climate bc amount of solar heat absorbed by tropical seas is consumed during the evaporation of surface water
    • Contributes to stability of temperature in lakes and ponds and provides mechanism that prevents terrestrial organisms for overheating
what are the 4 emergent properties of water expansion upon freezing
What are the 4 Emergent Properties of Water?Expansion Upon Freezing
  • Water is less dense as a solid than as a liquid
  • Ice Floats
  • Begins freezing when its molecules are no longer moving vigorously enough to break their hydrogen bonds
  • Above 4 degrees C acts like any other liquid, but below, freezes at 0 degrees locking the water molecules in place in their very structured arrangement
    • Becomes about 10% less dense
  • Creates H bonds at arms’ length from each other
  • When absorbs enough heat for water to rise above 0°C then the H bonds become disrupted
what are the 4 emergent properties of water expansion upon freezing1
What are the 4 Emergent Properties of Water?Expansion Upon Freezing
  • What happens after 0°C?
    • Water reaches its greatest density at 4°C and begins to expand as the molecules move faster
what are the 4 emergent properties of water expansion upon freezing2
What are the 4 Emergent Properties of Water?Expansion Upon Freezing
  • Benefits:
    • Fish get to survive in cold temperatures
    • We get cold drinks
what are the 4 emergent properties of water versatility as a solvent
What are the 4 Emergent Properties of Water?Versatility as a Solvent
  • Solution-
    • Liquid that is completely homogeneous mixture of two or more substances
  • Solvent-
    • Dissolving agent of a solution
  • Solute-
    • Substance that is dissolved
  • Aqueous solution-
    • Solution in which water is the solvent
what are the 4 emergent properties of water versatility as a solvent1
What are the 4 Emergent Properties of Water?Versatility as a Solvent
  • Why is water such a versatile solvent?
    • Due to polarity of the ions
    • Ions have mutual affinity through electrical attraction of the opposite charges
      • For this reason, water molecules surround the individual ions, separating and shielding them from one another, creating a hydration shell
        • Hydration shell- sphere of water molecules around each dissolved ion
    • Compounds don’t have to be ionic to dissolve water
      • Dissolve when water molecules surround each of the solute molecules, forming hydrogen bonds with them
what are the 4 emergent properties of water versatility as a solvent2
What are the 4 Emergent Properties of Water?Versatility as a Solvent
  • It’s ability to be such a great solvent, led to the creation of the two terms:
    • Hydrophilic
            • Any substance that has an affinity for water
            • Can be hydrophilic without dissolving-
              • Substances that are suspended in the aqueous solution create mixtures called: colloid
                • Stable suspension of fine particles in a liquid
    • Hydrophobic
            • Any substance that does not have an affinity for water
            • Generally substances that are nonionic and nonpolar
            • Seems to repel water
what are the 4 emergent properties of water versatility as a solvent3
What are the 4 Emergent Properties of Water?Versatility as a Solvent
  • Benefits:
        • Allows the movement of solvents through cohesion
        • Makes the solvent hydrophilic, benefitting cellular processes
how can you determine how many atoms and molecules are involved and present in an aqueous solution
How can you determine how many atoms and molecules are involved and present in an aqueous solution?
  • Use mass to calculate the number of molecules
  • Process:
    • Know:
      • Mass of each atom in molecule
    • Calculate:
      • Molecular Mass
        • Sum of masses of all the atoms in a molecule
how can you determine how many atoms and molecules are involved and present in an aqueous solution1
How can you determine how many atoms and molecules are involved and present in an aqueous solution?
    • Example:
      • C6H12O6 = Glucose
      • (12 daltons) x 6 + (1 daltons) x 12 + (16 daltons) x 6 = 72+12+96 = 180 daltons
      • Glucose has a molecular mass of 180 daltons
  • Not practical to measure out 1 molecule of something, instead we use mole
how can you determine how many atoms and molecules are involved and present in an aqueous solution2
How can you determine how many atoms and molecules are involved and present in an aqueous solution?
  • Know:
    • Mole = (mol) = represents an exact number of objects – 6.02 x 1023
      • 6.02 x 1023 = Avogadro’s number
      • There are 6.02 x 1023daltons in 1 gram
  • Calculate :
    • Molar mass
      • Use the molecular mass to determine the grams of the molecule to give 6.02 x 1023 molecules of the substance = 1 mol of the substance
how can you determine how many atoms and molecules are involved and present in an aqueous solution3
How can you determine how many atoms and molecules are involved and present in an aqueous solution?
  • Example:
    • Glucose has a molecular mass of 180 daltons
    • Therefore, there are 180 grams for 1 mol of glucose
  • What is the point of this?
    • If you want to make a 1:1 mixture of something, using mol makes it easier to create that mixture because you can’t just mix 10 grams of one and 10 grams of the other because it might not represent a 1:1 molecular mixture because the molecules have different weights
how can you determine how many atoms and molecules are involved and present in an aqueous solution4
How can you determine how many atoms and molecules are involved and present in an aqueous solution?
  • What if you wanted to make a solution?
    • Determine the molar mass and add enough water to bring the total volume of the solution up to 1 L = 1 Molar solution
    • Molarity= the number of moles of solute per liter of solution
what are acids and bases
What are Acids and Bases?
  • Hydrogen ion-
    • H+
    • Occurs when a hydrogen atom participating in a hydrogen bond between two water molecules shifts from one molecule to the other
    • Hydrogen atom leaves it electron behind
    • what is actually transferred is a hydrogen atom with a positive charge
      • a single proton with a charge of +1
what are acids and bases1
What are Acids and Bases?
  • hydroxide ion –
    • OH-
    • The water molecule that lost the proton
    • Has a charge of 1-
what are acids and bases2
What are Acids and Bases?
  • Hydronium ion –
    • H30+
    • Occurs when the proton binds to another water molecule
    • This reaction is reversible
what are acids and bases3
What are Acids and Bases?
  • Overall, what effect does this have?
    • H+ does not exist solitarily, always associated with another water molecule
    • The reversible reaction is generally at a dynamic equilibrium when water molecules dissociate at the same rate that they are being re-formed from H+ and OH-
    • These concentrations are equal in pure water
    • By themselves, H+ and OH- are very reactive
    • Adding solutes (Acids and Bases) disrupt the balance present in pure water
what are acids and bases4
What are Acids and Bases?
  • Acids
    • Acidic
    • When dissolve in water, donate additional H+ to solution
    • Substance that increases the hydrogen ion concentration of a solution
    • Example:
      • Hydrochloric acid (HCl)
what are acids and bases5
What are Acids and Bases?
  • Acids
    • Strong Acids-
      • Compounds that dissociate completely when mixed with water to increase the concentration of H+
      • Represented as a single arrow
    • Weak Acids-
      • Compounds that DO NOT dissociate completely when mixed with water, but still increase the concentration of H+
      • Represented as a double sided arrow
      • Accept back the Hydrogen ions
what are acids and bases6
What are Acids and Bases?
  • Bases
    • Basic
    • Reduces the hydrogen ion concentration of a solution
    • Have higher concentrations of OH- than H+
    • Some reduce H+ concentration by directly accepting hydrogen ions
      • Example:
        • Ammonia
    • Others reduce H+ concentration indirectly by dissociating to form hydroxide ions that combine with the H+ to form water
      • Example:
        • Sodium hydroxide
what are acids and bases7
What are Acids and Bases?
  • Bases
    • Strong base-
      • Compounds that dissociate completely when mixed with water to increase the concentration of OH-
      • Represented as a single arrow
    • Weak Bases-
      • Compounds that DO NOT dissociate completely when mixed with water, but still increase the concentration of OH-
      • Represented as a double sided arrow
      • Will release back the Hydrogen ions
what are acids and bases8
What are Acids and Bases?
  • Neutral solutions
    • H+ and OH- are equal
what is ph what exactly does it measure
What is pH? What exactly does it measure?
  • At any aqueous solution at 25°C, the product of the hydrogen and hydroxide ion concentrations is constant at 10-14
    • [H+][OH-] = 10-14
  • Neutral solutions =
    • [H+] = 10-7 and [OH-] = 10-7
    • 10-7 x 10-7 = 10-14
what is ph what exactly does it measure1
What is pH? What exactly does it measure?
  • What if:
    • [H+] = 10-5 (therefore, the number of H+ ion increases_?

10-5x 10-? = 10-14

what is ph what exactly does it measure2
What is pH? What exactly does it measure?
  • pH scale compresses the range of H+ and OH- concentrations by employing the logarithmic scale using logarithms
what is ph what exactly does it measure3
What is pH? What exactly does it measure?
  • the pH is defined as the negative logarithm (base 10) of the hydrogen ion concentration:
    • pH = - log [H+]
    • Neutral =
      • –log 10-7 = -(-7)= 7
      • pH of 7
    • Acid =
      • pH declines as the H+ concentration increases
      • pH of less than 7
    • Base =
      • pH of greater than 7
what is ph what exactly does it measure4
What is pH? What exactly does it measure?
  • based on H+ concentrations while implying OH- concentrations
  • each pH unit represents a tenfold difference in H+ and OH- concentrations
what is a buffer
What is a Buffer?
  • Help maintain a relatively constant pH in biological fluids despite the addition of acids or bases
  • Substances that minimize changes in the concentration of H+ and OH- in a solution when they have been depleted
  • Most contain a weak acid and its corresponding base
    • These combine reversibly with hydrogen ions
  • The chemical equilibrium created by buffers acts as a pH regulator in which the reaction shifts left or right as other processes in the solution add or remove hydrogen ions
what is a buffer1
What is a Buffer?
  • Example:
    • If the H+ concentration falls (increase in pH), the reaction shifts right
why are buffers important
Why are buffers important?
  • Even a slight change in pH can be harmful, because the chemical processes of the cell are very sensitive to the concentration of hydrogen and hydroxide ions
how can all of this information affect our water quality on earth
How can all of this information affect our water quality on Earth?
  • Most life is dependent on water
  • Actions:
    • Burning of fossil fuels
      • Releases gaseous compounds into the atmosphere, including copious amounts of CO2 which alter the delicate balance of conditions of life on Earth by affecting water pH and temperature. Major source of sulfur oxides and nitrous oxides that react with water in the air to form strong acids which fall to the Earth as rain or snow
how can all of this information affect our water quality on earth1
How can all of this information affect our water quality on Earth?
  • Results:
    • Acid precipitation- rain, snow, and fog with pH lower than 5.2
      • Carried by wind can affect not just the polluted areas, but also area miles away
        • Can affect the water supply
        • Can have adverse effects on land by affecting the soil chemistry
          • Effected many North American and European forests
how can all of this information affect our water quality on earth2
How can all of this information affect our water quality on Earth?
  • Results:
    • CO2 is the main produce of fossil fuel combustion
      • It’s released into the atmosphere, and ½ stays in the atmosphere
        • Acts like reflective blanket that prevents heat from radiating into outer space
          • Causes the greenhouse effect
        • Some is taken up by trees, but about 30% is absorbed by the ocean
          • Can harm marine life and ecosystems
            • Reacts with water to form carbonic acid which dissociates, producing protons and a balance between bicarbonate and carbonate
              • This process can affect the production of calcium carbonate by corals – needed for calcification in coral reefs