CH3 Water and Life
§A calorie (cal) is the amount of ________ required to raise the temperature of 1 g of _________ by 1°C §The "calories" on food packages are actually _____________ (kcal), where 1 kcal = __________ cal §The joule (J) is another unit of energy where 1 J = _____________ cal, or 1 cal = _________ J
§A calorie (cal) is the amount of heat required to raise the temperature of 1 g of water by 1°C §The "calories" on food packages are actually kilocalories (kcal), where 1 kcal = 1,000 cal §The joule (J) is another unit of energy where 1 J = 0.239 cal, or 1 cal = 4.184 J
Hydophilic and Hydrophobic Subs: §A ____________ substance is one that has anaffinity for water §A ____________ substance is one that does not have an affinity for water §Oil molecules are hydrophobic because they have relatively ____________ bonds §Hydrophobic molecules related to oils are the major ingredients of ______ ____________
§A hydrophilic substance is one that has anaffinity for water §A hydrophobic substance is one that does not have an affinity for water §Oil molecules are hydrophobic because they have relatively nonpolar bonds §Hydrophobic molecules related to oils are the major ingredients of cell membranes
Water: The Solvent of Life: §A ___________ is a liquid that is a completely homogeneous mixture of substances §A _________ is the dissolving agent of a solution §The ________ is the substance that is dissolved §An ____________ ___________ is one in which water is the solvent
§A solution is a liquid that is a completely homogeneous mixture of substances §A solvent is the dissolving agent of a solution §The solute is the substance that is dissolved §An aqueous solution is one in which water is the solvent
§An acid is any substance that increases the ____ concentration of a solution: §When hydrochloric acid is added to water, ___________ ions dissociate from chloride ions: HCl à H+ + Cl−. This produces an acidic solution.
§An acid is any substance that increases the H+ concentration of a solution: §When hydrochloric acid is added to water, hydrogen ions dissociate from chloride ions: HCl à H+ + Cl−. This produces an acidic solution.
Evaporative Cooling: §As a liquid evaporates, its remaining __________ cools, a process called evaporative cooling §Evaporative cooling of water helps stabilize temperatures in _______________ and ________ of water
§As a liquid evaporates, its remaining surface cools, a process called evaporative cooling §Evaporative cooling of water helps stabilize temperatures in organisms and bodies of water
Acidification: A Threat to Water Quality: §Human activities such as burning fossil fuels threaten water quality §________ is the main product of fossil fuel combustion §About 25% of human-generated CO2 is absorbed by the __________ §CO2 dissolved in sea water forms carbonic acid; this process is called __________ ____________
§Human activities such as burning fossil fuels threaten water quality §CO2 is the main product of fossil fuel combustion §About 25% of human-generated CO2 is absorbed by the oceans §CO2 dissolved in sea water forms carbonic acid; this process is called ocean acidification
Floating of Ice on Liquid Water: §Ice floats in liquid water because hydrogen bonds in ice are more "____________ ," making ice less ___________ than water §Water reaches its greatest density at _____°C §If ice sank, all bodies of water would eventually freeze solid, making life impossible on Earth Most materials ________ as they solidify, but water ___________.
§Ice floats in liquid water because hydrogen bonds in ice are more "ordered," making ice less dense than water §Water reaches its greatest density at 4°C §If ice sank, all bodies of water would eventually freeze solid, making life impossible on Earth Most materials contract as they solidify, but water expands.
The pH Scale: §In any aqueous solution at 25°C the product of H+ and OH− is constant and can be written as [H+][OH−] = _______ §In a neutral solution at room temperature, [H+] = _______ M and [OH−] = _______ M.
§In any aqueous solution at 25°C the product of H+ and OH− is constant and can be written as [H+][OH−] = 10− 14 §In a neutral solution at room temperature, [H+] = 10−7 M and [OH−] = 10−7 M.
Temperature and Heat §__________ __________ is the energy of motion §The kinetic energy associated with random ______ of atoms or molecules is called __________ __________ §Temperature is a measure of ___________ that represents the average ____________ energy of the molecules in a body of _________ §__________ is a measure of the total quantity of kinetic energy due to molecular motion in a body of matter. §Temperature measures the ___________ of heat in a body of matter due to the average ___________ energy of molecules.
§Kinetic energy is the energy of motion §The kinetic energy associated with random motion of atoms or molecules is called thermal energy §Temperature is a measure of energy that represents the average kinetic energy of the molecules in a body of matter §Heat is a measure of the total quantity of kinetic energy due to molecular motion in a body of matter. §Temperature measures the intensity of heat in a body of matter due to the average kinetic energy of molecules.
§_________ _______ is the sum of all masses of all atoms in a molecule §Numbers of molecules are usually measured in moles, where 1 _____ (mol) = 6.02 ´ 1023 molecules §Avogadro's number and the unit dalton were defined such that 6.02 ´ 1023 daltons = _____ §__________ (M) is the number of moles of soluteper liter of solution
§Molecular mass is the sum of all masses of all atoms in a molecule §Numbers of molecules are usually measured in moles, where 1 mole (mol) = 6.02 ´ 1023 molecules §Avogadro's number and the unit dalton were defined such that 6.02 ´ 1023 daltons = 1 g §Molarity (M) is the number of moles of soluteper liter of solution
Solute Concentration in Aqueous Solutions: §Most chemical reactions in organisms involve __________ dissolved in water §When carrying out experiments, we use ______ to calculate the number of solute molecules in an aqueous solution •Biological chemistry is "wet" chemistry, with most reactions involving solutes dissolved in _________. •Chemical reactions depend on collisions of molecules and therefore on the concentrations of solutes in aqueous solution.
§Most chemical reactions in organisms involve solutes dissolved in water §When carrying out experiments, we use mass to calculate the number of solute molecules in an aqueous solution •Biological chemistry is "wet" chemistry, with most reactions involving solutes dissolved in water. •Chemical reactions depend on collisions of molecules and therefore on the concentrations of solutes in aqueous solution.
§___________ __________ is a measure of how hard it is to break the surface of a liquid §Water has an unusually high surface tension due to __________ bonding between the molecules at the _____-_______ ____________ and to the _________ below
§Surface tension is a measure of how hard it is to break the surface of a liquid §Water has an unusually high surface tension due to hydrogen bonding between the molecules at the air-water interface and to the water below
Weight of 1 mole of sucrose? §The chemical formula is C12H22O11 §A carbon atom weighs____ daltons, §hydrogen ___ dalton, and §oxygen ___ daltons. §12x12= 144 §1x22=22 §16x11=176 §144+22+176=342 daltons §How much sucrose do you need to weigh out to make 1 mole of sucrose?
§The chemical formula is C12H22O11 §A carbon atom weighs 12 daltons, §hydrogen 1 dalton, and §oxygen 16 daltons. §12x12= 144 §1x22=22 §16x11=176 §144+22+176=342 daltons -The sum of the weight of all of the atoms in sucrose, or the molecular weight of sucrose. --> 342 grams
Buffers: §The internal pH of most living cells must remain close to pH 7 §Buffers are substances that ____________ changes in concentrations of H+ and OH− in a solution §Most buffer solutions contain a _______ acid and its corresponding ________ , which combine reversibly with H+ ions
§The internal pH of most living cells must remain close to pH 7 §Buffers are substances that minimize changes in concentrations of H+ and OH− in a solution §Most buffer solutions contain a weak acid and its corresponding base, which combine reversibly with H+ ions
§The pH of a solution is defined by the negative logarithm of H+ concentration, written as pH = − log [H+] §For a neutral aqueous solution, [H+] is 10−7, so pH = −(− 7) = 7
§The pH of a solution is defined by the negative logarithm of H+ concentration, written as pH = − log [H+] §For a neutral aqueous solution, [H+] is 10−7, so pH = −(− 7) = 7
Water's Specific Heat: §The specific heat of a substance is the amount of heat that must be ___________ or ________ for 1 g of that substance to change its temperature by _____ §The specific heat of water is ______ cal/g/°C §Water resists changing its temperature because of its high specific heat
§The specific heat of a substance is the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1°C §The specific heat of water is 1 cal/g/°C §Water resists changing its temperature because of its high specific heat
§Though statistically rare, the dissociation of water molecules has a great effect on organisms §Changes in concentrations of H+ and OH− can drastically affect the chemistry of a __________ §Adding certain solutes, called ____ and ______, modifies the concentrations of H+ and OH− (equal in pure water)
§Though statistically rare, the dissociation of water molecules has a great effect on organisms §Changes in concentrations of H+ and OH− can drastically affect the chemistry of a cell §Adding certain solutes, called acids and bases, modifies the concentrations of H+ and OH−
§Water can also dissolve compounds made of ________ __________ molecules §Even large polar molecules such as proteinscan dissolve in water if they have) ________ and ________ regions
§Water can also dissolve compounds made of nonionic polar molecules §Even large polar molecules such as proteinscan dissolve in water if they have ionic andpolar regions
§Water is a versatile solvent due to its ___________ §When an ionic compound is dissolved in water, each ion is surrounded by a sphere of water molecules called a __________ ___________
§Water is a versatile solvent due to its polarity §When an ionic compound is dissolved in water, each ion is surrounded by a sphere of water molecules called a hydration shell
§Water is in a state of dynamic equilibrium in which water molecules __________ at the same rate at which they are being ___________
§Water is in a state of dynamic equilibrium in which water molecules dissociate at the same rate at which they are being reformed
§Water's high specific heat is due to ____________ _____________. §Heat must be _________ to break hydrogen bonds, and heat is ___________ when hydrogen bonds form. §The high specific heat of water minimizes temperature fluctuations to within limits that permit life
§Water's high specific heat is due to hydrogen bonding. §Heat must be absorbed to break hydrogen bonds, and heat is released when hydrogen bonds form. §The high specific heat of water minimizes temperature fluctuations to within limits that permit life
•A large body of water can absorb a large amount of heat from the sun during the daytime in the summer and yet warm only a few degrees. •At night and during the winter, the warm water heats the cooler air. •Therefore, the oceans and coastal land areas have more ___________ temperatures than inland areas. •Living things are made of primarily water, so they ___________ changes in temperature better than they would if composed of a liquid with a lower specific heat.
•A large body of water can absorb a large amount of heat from the sun during the daytime in the summer and yet warm only a few degrees. •At night and during the winter, the warm water heats the cooler air. •Therefore, the oceans and coastal land areas have more stable temperatures than inland areas. •Living things are made of primarily water, so they resist changes in temperature better than they would if composed of a liquid with a lower specific heat.
•_____ ___________is rain, snow, or fog with a pH below 5.2. •Acid precipitation can damage aquatic life and also adversely affects land plants by changing soil ___________. •The United States passed the Clean Air Act in 1990, mandating improved industrial technologies to reduce the release of harmful chemical pollutants.
•Acid precipitation is rain, snow, or fog with a pH below 5.2. •Acid precipitation can damage aquatic life and also adversely affects land plants by changing soil chemistry. •The United States passed the Clean Air Act in 1990, mandating improved industrial technologies to reduce the release of harmful chemical pollutants.
•As seawater acidifies, the extra hydrogen ions combine with ____________ ions (CO32-) to form bicarbonate ions (HCO3-). •Scientists predict that ocean acidification will cause carbonate concentrations in the oceans to decrease by ____% over this century. •____________ , the production of calcium carbonate (CaCO3) by corals and other organisms, is directly affected by the concentration of CO32-. •The burning of fossil fuels is also a major source of sulfur oxides and nitrous oxides. •These oxides react with water to form strong acids, which fall to Earth with rain or snow.
•As seawater acidifies, the extra hydrogen ions combine with carbonate ions (CO32-) to form bicarbonate ions (HCO3-). •Scientists predict that ocean acidification will cause carbonate concentrations in the oceans to decrease by 40% over this century. •Calcification, the production of calcium carbonate (CaCO3) by corals and other organisms, is directly affected by the concentration of CO32-. •The burning of fossil fuels is also a major source of sulfur oxides and nitrous oxides. •These oxides react with water to form strong acids, which fall to Earth with rain or snow.
•At equilibrium, the concentration of _________ molecules greatly exceeds the concentration of H+ and OH−. •In pure water, only _____ water molecule in every 554 million is dissociated. •At equilibrium, the concentration of H+ or OH− is 10−7 M (at 25°C). •There is only one ____-millionth of a mole of hydrogen ions per liter of pure water and an equal number of hydroxide ions.
•At equilibrium, the concentration of water molecules greatly exceeds the concentration of H+ and OH−. •In pure water, only one water molecule in every 554 million is dissociated. •At equilibrium, the concentration of H+ or OH− is 10−7 M (at 25°C). •There is only one ten-millionth of a mole of hydrogen ions per liter of pure water and an equal number of hydroxide ions.
•________ and _________________ are related but not identical. •Heat depends in part on the matter's _________, while __________ is the average kinetic energy of molecules, regardless of volume. •When two objects of different temperatures come together, heat passes from the __________ object to the ___________ object until the two are the same temperature. •Molecules in the cooler object ______________ up at the expense of the kinetic energy of the warmer object. •Ice cubes cool a glass of soda by _____________ heat from the ___________ as the ice melts.
•Heat and temperature are related but not identical. •Heat depends in part on the matter's volume, while temperature is the average kinetic energy of molecules, regardless of volume. •When two objects of different temperatures come together, heat passes from the warmer object to the cooler object until the two are the same temperature. •Molecules in the cooler object speed up at the expense of the kinetic energy of the warmer object. •Ice cubes cool a glass of soda by absorbing heat from the soda as the ice melts.
•Hydrophilic substances are dominated by ________ or __________ bonds. •Some hydrophilic substances do not dissolve because their molecules are too ___________. •For example, cotton is hydrophilic because cellulose, its major constituent, has numerous __________ _______________ bonds. However, its giant cellulose molecules are too large to dissolve in water. •Water molecules form __________ _________ with the cellulose fibers of cotton. When you dry yourself with a cotton towel, the water is pulled into the towel.
•Hydrophilic substances are dominated by ionic or polar bonds. •Some hydrophilic substances do not dissolve because their molecules are too large. •For example, cotton is hydrophilic because cellulose, its major constituent, has numerous polar covalent bonds. However, its giant cellulose molecules are too large to dissolve in water. •Water molecules form hydrogen bonds with the cellulose fibers of cotton. When you dry yourself with a cotton towel, the water is pulled into the towel.
•Hydrophobic substances are _____________ and have ____________ ____________ bonds. •Because no regions consistently have partial or full _________ , water molecules cannot form hydrogen bonds with hydrophobic molecules. •Oils such as vegetable oil are hydrophobic because the dominant bonds, carbon-carbon and carbon-hydrogen, share electrons ________.
•Hydrophobic substances are nonionic and have nonpolar covalent bonds. •Because no regions consistently have partial or full charges, water molecules cannot form hydrogen bonds with hydrophobic molecules. •Oils such as vegetable oil are hydrophobic because the dominant bonds, carbon-carbon and carbon-hydrogen, share electrons equally.
•If ice sank, eventually all ponds, lakes, and even oceans would _________ solid. •During the summer, only the upper few _________________ of oceans would thaw. •Instead, the surface layer of ice ____________ the liquid water below, preventing it from freezing and allowing life to exist under the frozen surface. •Ice also provides solid habitat for Arctic animals like polar bears and seals.
•If ice sank, eventually all ponds, lakes, and even oceans would freeze solid. •During the summer, only the upper few centimeters of oceans would thaw. •Instead, the surface layer of ice insulates the liquid water below, preventing it from freezing and allowing life to exist under the frozen surface. •Ice also provides solid habitat for Arctic animals like polar bears and seals.
•If substance A has a molecular weight of 10 daltons and substance B has a molecular weight of 5 daltons. A mole (mol) is equal to the molecular weight of a substance but scaled up from daltons to grams. •So 10 grams of substance A has 6.02 x1023 molecules and 5 grams of substance B has 6.02 x1023 molecules •A carbon atom weighs 12 daltons, hydrogen 1 dalton, and oxygen 16 daltons.
•If substance A has a molecular weight of 10 daltons and substance B has a molecular weight of 5 daltons. A mole (mol) is equal to the molecular weight of a substance but scaled up from daltons to grams. •So 10 grams of substance A has 6.02 x1023 molecules and 5 grams of substance B has 6.02 x1023 molecules •A carbon atom weighs 12 daltons, hydrogen 1 dalton, and oxygen 16 daltons.
•Most biological fluids have pH values in the range 6-8. •However, the human stomach has strongly acidic digestive juice with a pH of about 2. •Each pH unit represents a __________ difference in H+ and OH− concentrations. •A small change in pH indicates a substantial change in H+ and OH− concentrations. •A solution of pH 3 is not twice as acidic as a solution of pH 6 but a _________ times more acidic.
•Most biological fluids have pH values in the range 6-8. •However, the human stomach has strongly acidic digestive juice with a pH of about 2. •Each pH unit represents a tenfold difference in H+ and OH− concentrations. •A small change in pH indicates a substantial change in H+ and OH− concentrations. •A solution of pH 3 is not twice as acidic as a solution of pH 6 but a thousand times more acidic.
•The most _______________ molecules are the most likely to evaporate, leaving the ________ -kinetic energy molecules behind. •Evaporative cooling moderates temperature in _________ and ponds. •Evaporation of sweat in mammals or evaporation of water from the leaves of plants removes excess _________ and prevents terrestrial organisms from _______________ .
•The most energetic molecules are the most likely to evaporate, leaving the lower-kinetic energy molecules behind. •Evaporative cooling moderates temperature in lakes and ponds. •Evaporation of sweat in mammals or evaporation of water from the leaves of plants removes excess heat and prevents terrestrial organisms from overheating.
•The pH of a solution is defined as the negative logarithm (base 10) of the hydrogen ion concentration. •pH = −log [H+] or [H+] = 10−pH •In a neutral solution, [H+] = 10−7 M and pH = 7. •The pH decreases as the H+ concentration increases.
•The pH of a solution is defined as the negative logarithm (base 10) of the hydrogen ion concentration. •pH = −log [H+] or [H+] = 10−pH •In a neutral solution, [H+] = 10−7 M and pH = 7. •The pH decreases as the H+ concentration increases.
Vaporization: •Vaporization occurs when a molecule moves fast enough to overcome the ______________ of other molecules in the liquid. •The _________ of molecular movement varies; temperature is the average kinetic energy of molecules. •Even in a low-temperature liquid (with low average _________ energy), some molecules move fast enough to evaporate. •Heating a liquid increases the average kinetic energy and increases the rate of evaporation.
•Vaporization occurs when a molecule moves fast enough to overcome the attraction of other molecules in the liquid. •The speed of molecular movement varies; temperature is the average kinetic energy of molecules. •Even in a low-temperature liquid (with low average kinetic energy), some molecules move fast enough to evaporate. •Heating a liquid increases the average kinetic energy and increases the rate of evaporation.
•Water begins to freeze when its molecules are no longer __________ vigorously enough to break their hydrogen bonds. •When water reaches 0°C, it becomes locked into a ___________ __________, with each water molecule bonded to four partners. •As ice starts to melt, some of the hydrogen bonds break, and water molecules can slip ___________ together than they can while in the ice state. •Ice is about ____% less dense than water at 4°C. Therefore, ice floats on the cool water below.
•Water begins to freeze when its molecules are no longer moving vigorously enough to break their hydrogen bonds. •When water reaches 0°C, it becomes locked into a crystalline lattice, with each water molecule bonded to four partners. •As ice starts to melt, some of the hydrogen bonds break, and water molecules can slip closer together than they can while in the ice state. •Ice is about 10% less dense than water at 4°C. Therefore, ice floats on the cool water below.
•Water has a relatively high heat of vaporization, with about _______ cal of heat required to evaporate 1 g of water at room temperature. •This is double the amount of heat required to vaporize the same quantity of __________ or ammonia. •The heat of vaporization is high because _________ ______________ must be broken before a water molecule can evaporate from the liquid.
•Water has a relatively high heat of vaporization, with about 580 cal of heat required to evaporate 1 g of water at room temperature. •This is double the amount of heat required to vaporize the same quantity of alcohol or ammonia. •The heat of vaporization is high because hydrogen bonds must be broken before a water molecule can evaporate from the liquid.
•Water is an effective solvent because it readily forms hydrogen bonds with ___________ and _______ ____________ molecules. •For example, when a crystal of salt (NaCl) is placed in water, the Na+ cations interact with the partial negative charges of the oxygen regions of water molecules. •The Cl− anions interact with the partial positive charges of the hydrogen regions of water molecules. -Eventually, water dissolves all the _________ , resulting in a solution with two solutes: sodium and chloride ions.
•Water is an effective solvent because it readily forms hydrogen bonds with charged and polar covalent molecules. •For example, when a crystal of salt (NaCl) is placed in water, the Na+ cations interact with the partial negative charges of the oxygen regions of water molecules. •The Cl− anions interact with the partial positive charges of the hydrogen regions of water molecules. -Eventually, water dissolves all the ions, resulting in a solution with two solutes: sodium and chloride ions.
•Water molecules move up from the roots to the leaves of a plant through water-_____________ vessels. •As water molecules ____________ from a leaf, other water molecules from vessels in the leaf __________ them. •Hydrogen bonds cause water molecules leaving the vessels to ________ on molecules farther down. •This upward pull is transmitted down to the _________. •Adhesion, the clinging of one substance to another, also contributes, as water adheres to the ___________ of the vessels.
•Water molecules move up from the roots to the leaves of a plant through water-conducting vessels. •As water molecules evaporate from a leaf, other water molecules from vessels in the leaf replace them. •Hydrogen bonds cause water molecules leaving the vessels to tug on molecules farther down. •This upward pull is transmitted down to the roots. •Adhesion, the clinging of one substance to another, also contributes, as water adheres to the walls of the vessels.
•When water is in its liquid form, its hydrogen bonds are very ____________, about one-twentieth as strong as ____________ bonds. •Hydrogen bonds form, ..... , and re-form with great frequency. •Each hydrogen bond lasts only a few ____________________ of a second, but the molecules continuously form new hydrogen bonds with a succession of partners. •At any given instant, a substantial percentage of all water molecules are hydrogen-bonded to their neighbors.
•When water is in its liquid form, its hydrogen bonds are very fragile, about one-twentieth as strong as covalent bonds. •Hydrogen bonds form, break, and re-form with great frequency. •Each hydrogen bond lasts only a few trillionths of a second, but the molecules continuously form new hydrogen bonds with a succession of partners. •At any given instant, a substantial percentage of all water molecules are hydrogen-bonded to their neighbors.
Moderation Temperature by Water: §Water absorbs heat from warmer air and releases _________ heat to cooler air §Water can absorb or release a large amount of heat with only a slight change in its own ____________
§Water absorbs heat from warmer air and releases stored heat to cooler air §Water can absorb or release a large amount of heat with only a slight change in its own temperature
•At the level of the organism, water's high heat of vaporization accounts for the severity of _________ burns. •Steam burns are caused by the heat energy ____________ when steam condenses to liquid on the skin.
•At the level of the organism, water's high heat of vaporization accounts for the severity of steam burns. •Steam burns are caused by the heat energy released when steam condenses to liquid on the skin.
- Because the oxygen is more electronegative than hydrogen, a water molecule is a polar molecule in which opposite ends of the molecule have _________ charges -oxygen regions have partial __________ charge -hydrogen regions have partial ______ charge
-Because the oxygen is more electronegative than hydrogen, a water molecule is a polar molecule in which opposite ends of the molecule have oppotsife charges -oxygen regions have partial negative charge -hydrogen regions have partial positive charge
Heat of Vaporization and Evaporation:
-Heat of vaporization is the heat a liquid must absorb for 1 g to be converted to gas -Evaporation is transformation of a substance from liquid to gas
Polar covalent bonds in water molecules result in hydrogen bonding -In the water molecule, the electrons of the polar covalent bonds spend more time near the oxygen than the hydrogen -the water molecule is a ______ _______ (unevenly distributed) -_________ allows water molecules to form hydrogen bonds with each other
-In the water molecule, the electrons of the polar covalent bonds spend more time near the oxygen than the hydrogen -the water molecule is a polar molecule (unevenly distributed) -Polarity allows water molecules to form hydrogen bonds with each other
-Water has a variety of unusual properties because of the attraction between ______ water molecules. -The slightly negative regions of one water molecule are attracted to the slightly positive regions of nearby water molecules, forming _______________ bonds. -Each water molecule can form hydrogen bonds with as many as ________ neighbors.
-Water has a variety of unusual properties because of the attraction between polar water molecules. -The slightly negative regions of one water molecule are attracted to the slightly positive regions of nearby water molecules, forming hydrogen bonds. -Each water molecule can form hydrogen bonds with as many as four neighbors.
-When CO2 dissolves in seawater, it can react with water (H20) to form ________ ______ (H2CO3). --This weak acid lowers the pH of seawater, a process known as __________ _____________. -Based on measurements of CO2 levels in air bubbles trapped in ice over thousands of years, scientists calculate that the pH of the oceans is 0.1 pH units lower now than any time in the past 420,000 years. -Recent studies predict it will drop another 0.3-0.5 pH units by 2100.
-When CO2 dissolves in seawater, it can react with water (H20) to form carbonic acid (H2CO3). --This weak acid lowers the pH of seawater, a process known as ocean acidification. -Based on measurements of CO2 levels in air bubbles trapped in ice over thousands of years, scientists calculate that the pH of the oceans is 0.1 pH units lower now than any time in the past 420,000 years. -Recent studies predict it will drop another 0.3-0.5 pH units by 2100.
How does the habitat of a seam depend on the chemistry of water?
-most cells are sureonded by water -cells are 70-95% -is a reactant in many of the chemical reactions of life
Water
-only common substance to exist in the environment in all three states of matter -the structure of water alows it to interact wigj other molecules -waters uniqure emergent properties help make eath suitable for life
Acidic and basic conditions affect living organisms: §A hydrogen atom in a hydrogen bond between two water molecules can shift from one to the other §The hydrogen atom leaves its electron behind and is transferred as a ____________ , or hydrogen ion (H+) §The molecule that _________ the proton is now a hydroxide ion (OH−) §The molecule with the extra proton is now a ____________ ion (H3O+), though it is often represented as H+
Acidic and basic conditions affect living organisms: §A hydrogen atom in a hydrogen bond between two water molecules can shift from one to the other §The hydrogen atom leaves its electron behind and is transferred as a proton, or hydrogen ion (H+) §The molecule that lost the proton is now a hydroxide ion (OH−) §The molecule with the extra proton is now a hydronium ion (H3O+), though it is often represented as H+
Acids and Bases: §Any substance that reduces the hydrogen ion concentration in a solution is a _________ . §Some bases reduce the H+ concentration directly by ___________ hydrogen ions. §Ammonia (NH3) acts as a base when the nitrogen's unshared electron pair attracts a hydrogen ion from the solution, creating an ammonium ion (NH4+): NH3 + H+ Û NH4+. §Other bases reduce the H+ concentration indirectly by dissociating to ______, which then combines with H+ to form water. §NaOH --> Na+ + OH− §OH− + H+ --> H2O Weak acids and bases reversibly _______________ and _________ back hydrogen ions, but can still shift the balance of H+ and OH− away from neutrality
Acids and Bases: §Any substance that reduces the hydrogen ion concentration in a solution is a base. §Some bases reduce the H+ concentration directly by accepting hydrogen ions. §Ammonia (NH3) acts as a base when the nitrogen's unshared electron pair attracts a hydrogen ion from the solution, creating an ammonium ion (NH4+): NH3 + H+ Û NH4+. §Other bases reduce the H+ concentration indirectly by dissociating to OH−, which then combines with H+ to form water. §NaOH à Na+ + OH− §OH− + H+ à H2O Weak acids and bases reversibly release and accept back hydrogen ions, but can still shift the balance of H+ and OH− away from neutrality
Cohesion : §Collectively, ______________ bonds hold water molecules together, a phenomenon called ___________ §Cohesion helps the ___________ of water against gravity in plants §______________ is an attraction between different substances, for example, between water and plant cell walls
Cohesion : §Collectively, hydrogen bonds hold water molecules together, a phenomenon called cohesion §Cohesion helps the transport of water against gravity in plants §Adhesion is an attraction between different substances, for example, between water and plant cell walls
Four of water's properties that facilitate an environment for life are §___________ behavior §Ability to _________ ______________ §_____________ upon___________ §Versatility as a ______________
Four of water's properties that facilitate an environment for life are §Cohesive behavior §Ability to moderate temperature §Expansion upon freezing §Versatility as a solvent
The large amount of energy required to vaporize water has a wide range of effects.: •Water's high heat of vaporization moderates ____________. •Much of the sun's heat absorbed by tropical oceans is used for the _____________ of _________ water. •As moist tropical air moves to the poles, water vapor condenses to form ________ , releasing ___________.
The large amount of energy required to vaporize water has a wide range of effects.: •Water's high heat of vaporization moderates climate. •Much of the sun's heat absorbed by tropical oceans is used for the evaporation of surface water. •As moist tropical air moves to the poles, water vapor condenses to form rain, releasing heat.
The transformation of a molecule from a liquid to a gas is called _____________ or / ______________
The transformation of a molecule from a liquid to a gas is called vaporization, or evaporation.
