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Copyright  2010 Scott A. Bowling. Chapter 3: What’s so great about water? Life as we know it requires water: all organisms mostly liquid water all organisms.

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Presentation on theme: "Copyright  2010 Scott A. Bowling. Chapter 3: What’s so great about water? Life as we know it requires water: all organisms mostly liquid water all organisms."— Presentation transcript:

1 Copyright  2010 Scott A. Bowling. Chapter 3: What’s so great about water? Life as we know it requires water: all organisms mostly liquid water all organisms mostly liquid water most metabolism requires aqueous (water) medium most metabolism requires aqueous (water) medium many organisms live in liquid water or in an environment dominated by water in its various states (solid, liquid, or gas) many organisms live in liquid water or in an environment dominated by water in its various states (solid, liquid, or gas)

2 Copyright  2010 Scott A. Bowling. Chapter 3: What’s so great about water? Some numbers: cells are typically 70% or more water by mass cells are typically 70% or more water by mass about 75% of the Earth’s surface is covered by liquid water about 75% of the Earth’s surface is covered by liquid water

3 Copyright  2010 Scott A. Bowling. Chapter 3: What’s so great about water? Some numbers: cells are typically 70% or more water by mass cells are typically 70% or more water by mass about 75% of the Earth’s surface is covered by liquid water about 75% of the Earth’s surface is covered by liquid water But then, just being common on the Earth doesn’t make something essential for life. A large percentage of the Earth’s crust is sand, but we don’t consider sand a requirement for life.

4 Copyright  2010 Scott A. Bowling. Chapter 3: What’s so great about water? Some numbers: cells are typically 70% or more water by mass cells are typically 70% or more water by mass about 75% of the Earth’s surface is covered by liquid water about 75% of the Earth’s surface is covered by liquid water But then, just being common on Earth doesn’t make something essential for life. A large percentage of the Earth’s crust is sand, but we don’t consider sand a requirement for life. What is it about water that makes it so special?

5 Copyright  2010 Scott A. Bowling. Chapter 3: What’s so great about water? polar nature of water molecules polar nature of water molecules What properties of water are important for life? What properties of water are important for life? Acids and Bases Acids and Bases Some useful definitions Some useful definitions

6 Copyright  2010 Scott A. Bowling. Chapter 3: What’s so great about water? polar nature of water molecules polar nature of water molecules What properties of water are important for life? What properties of water are important for life? Acids and Bases Acids and Bases Some useful definitions Some useful definitions

7 Copyright  2010 Scott A. Bowling. Draw a water molecule (structural formula) Then draw in four more around it that are connected to it by hydrogen bonds.

8 Copyright  2010 Scott A. Bowling. polar nature of water molecules oxygen atoms are electron seeking (electronegative), especially compared to hydrogen; thus for an oxygen-hydrogen bond: oxygen atoms are electron seeking (electronegative), especially compared to hydrogen; thus for an oxygen-hydrogen bond: the oxygen atom has a partial (-) charge the oxygen atom has a partial (-) charge the hydrogen atoms have a partial (+) charge the hydrogen atoms have a partial (+) charge

9 Copyright  2010 Scott A. Bowling. polar nature of water molecules the polar character of water allows water molecules to form up to 4 hydrogen bonds

10 Copyright  2010 Scott A. Bowling. Draw a water molecule (structural formula) Then draw in four more around it that are connected to it by hydrogen bonds.

11 Copyright  2010 Scott A. Bowling. Chapter 3: What’s so great about water? polar nature of water molecules polar nature of water molecules What properties of water are important for life? What properties of water are important for life? Acids and Bases Acids and Bases Some useful definitions Some useful definitions

12 Copyright  2010 Scott A. Bowling. List and describe at least four properties of water that result from its polar nature/hydrogen bonds. Describe how water acts as a temperature buffer (creates temperature stability).

13 Copyright  2010 Scott A. Bowling. What properties of water are important for life? all of this come in some way from water’s polar nature  hydrogen bonds and similar interactions all of this come in some way from water’s polar nature  hydrogen bonds and similar interactions water is the principal solvent in living things water is the principal solvent in living things water exhibits both cohesive and adhesive forces water exhibits both cohesive and adhesive forces water helps maintain a stable temperature water helps maintain a stable temperature ice (solid water) floats in liquid water ice (solid water) floats in liquid water

14 Copyright  2010 Scott A. Bowling. water is the principal solvent in living things highly polar = excellent solvent for other polar substances, and for ionic compounds highly polar = excellent solvent for other polar substances, and for ionic compounds

15 Copyright  2010 Scott A. Bowling. water is the principal solvent in living things hydrophilic substances – interact readily with water hydrophilic substances – interact readily with water hydrophobic substances – do not interact readily with water hydrophobic substances – do not interact readily with water nonpolar substances nonpolar substances good components for membranes good components for membranes

16 Copyright  2010 Scott A. Bowling. water exhibits both cohesive and adhesive forces cohesive forces: attraction of water molecules each other cohesive forces: attraction of water molecules each other give water a high surface tension give water a high surface tension

17 Copyright  2010 Scott A. Bowling. water exhibits both cohesive and adhesive forces adhesive forces: water molecules to be attracted to other kinds of molecules adhesive forces: water molecules to be attracted to other kinds of molecules how things are made wet how things are made wet capillary action: water moving through narrow tubes even against gravity capillary action: water moving through narrow tubes even against gravity results from cohesion and adhesion results from cohesion and adhesion living organisms take advantage of this living organisms take advantage of this

18 Copyright  2010 Scott A. Bowling. water helps maintain a stable temperature high specific heat of water  temp. stability high specific heat of water  temp. stability specific heat – energy to raise the temp. of 1 gram of something 1ºC specific heat – energy to raise the temp. of 1 gram of something 1ºC h-bonds make water specific heat high h-bonds make water specific heat high 1 calorie / gram ºC 1 calorie / gram ºC comparatively, takes more energy gain/loss to change water temp. comparatively, takes more energy gain/loss to change water temp.

19 Copyright  2010 Scott A. Bowling. water helps maintain a stable temperature high specific heat of water  temp. stability high specific heat of water  temp. stability much of the ecosphere is water much of the ecosphere is water most biological organisms >70% water most biological organisms >70% water temperature stability is critical for most life temperature stability is critical for most life

20 Copyright  2010 Scott A. Bowling. water helps maintain a stable temperature high heat of vaporization of water helps cool the ecosphere and biological organisms high heat of vaporization of water helps cool the ecosphere and biological organisms heat of vaporization: energy to move 1 gram from liquid to gas heat of vaporization: energy to move 1 gram from liquid to gas

21 Copyright  2010 Scott A. Bowling. water helps maintain a stable temperature high heat of vaporization of water helps cool the ecosphere and biological organisms high heat of vaporization of water helps cool the ecosphere and biological organisms heat of vaporization: energy to move 1 gram from liquid to gas heat of vaporization: energy to move 1 gram from liquid to gas h-bonds make water specific heat high h-bonds make water specific heat high 540 calories / gram 540 calories / gram

22 Copyright  2010 Scott A. Bowling. water helps maintain a stable temperature high heat of vaporization of water helps cool the ecosphere and biological organisms high heat of vaporization of water helps cool the ecosphere and biological organisms heat of vaporization: energy to move 1 gram from liquid to gas heat of vaporization: energy to move 1 gram from liquid to gas h-bonds make water specific heat high h-bonds make water specific heat high 540 calories / gram 540 calories / gram organisms use this for cooling organisms use this for cooling examples: sweating; evaporative cooling of a leaf examples: sweating; evaporative cooling of a leaf

23 Copyright  2010 Scott A. Bowling. Describe how water acts as a temperature buffer (creates temperature stability).

24 Copyright  2010 Scott A. Bowling.

25 . ice floats liquid water becomes denser as it cools – but only up to a point liquid water becomes denser as it cools – but only up to a point

26 Copyright  2010 Scott A. Bowling. ice floats liquid water becomes denser as it cools – but only up to a point liquid water becomes denser as it cools – but only up to a point at 4ºC: water begins to expand as it cools further – that is, it gets less dense from then on – due to hydrogen bonds becoming locked in place water begins to expand as it cools further – that is, it gets less dense from then on – due to hydrogen bonds becoming locked in place

27 Copyright  2010 Scott A. Bowling. ice floats at 0ºC: ice freezes into a crystal ice freezes into a crystal

28 Copyright  2010 Scott A. Bowling. ice floats at 0ºC: ice freezes into a crystal ice freezes into a crystal based on the hydrogen bonds based on the hydrogen bonds

29 Copyright  2010 Scott A. Bowling. ice floats at 0ºC: ice freezes into a crystal ice freezes into a crystal based on the hydrogen bonds based on the hydrogen bonds floating ice keeps lakes, etc., from freezing solid and is important for temperature cycling on the planet floating ice keeps lakes, etc., from freezing solid and is important for temperature cycling on the planet

30 Copyright  2010 Scott A. Bowling. List and describe at least four properties of water that result from its polar nature/hydrogen bonds.

31 Copyright  2010 Scott A. Bowling. Chapter 3: What’s so great about water? polar nature of water molecules polar nature of water molecules What properties of water are important for life? What properties of water are important for life? Acids and Bases Acids and Bases Some useful definitions Some useful definitions

32 Copyright  2010 Scott A. Bowling. Define acids and bases.

33 Copyright  2010 Scott A. Bowling. Acids and Bases acids are proton donors acids are proton donors

34 Copyright  2010 Scott A. Bowling. Acids and Bases acids are proton donors acids are proton donors dissociates to yield hydrogen ions (H + ) in solution dissociates to yield hydrogen ions (H + ) in solution HA (an acid) H + + A - (an anion)

35 Copyright  2010 Scott A. Bowling. Acids and Bases acids are proton donors acids are proton donors dissociates to yield hydrogen ions (H + ) in solution dissociates to yield hydrogen ions (H + ) in solution HA (an acid) H + + A - (an anion) H + = one proton (mostly) H + = one proton (mostly)

36 Copyright  2010 Scott A. Bowling. Acids and Bases acids are proton donors acids are proton donors dissociates to yield hydrogen ions (H + ) in solution dissociates to yield hydrogen ions (H + ) in solution HA (an acid) H + + A - (an anion) H + = one proton (mostly) H + = one proton (mostly) when the atom loses its electron to become a hydrogen ion, all that remains is the nucleus when the atom loses its electron to become a hydrogen ion, all that remains is the nucleus

37 Copyright  2010 Scott A. Bowling. Acids and Bases acids are proton donors acids are proton donors dissociates to yield hydrogen ions (H + ) in solution dissociates to yield hydrogen ions (H + ) in solution HA (an acid) H + + A - (an anion) H + = one proton (mostly) H + = one proton (mostly) when the atom loses its electron to become a hydrogen ion, all that remains is the nucleus when the atom loses its electron to become a hydrogen ion, all that remains is the nucleus thus, hydrogen ions are sometimes referred to as protons thus, hydrogen ions are sometimes referred to as protons

38 Copyright  2010 Scott A. Bowling. Acids and Bases acids are proton donors acids are proton donors dissociates to yield hydrogen ions (H + ) in solution dissociates to yield hydrogen ions (H + ) in solution HA (an acid) H + + A - (an anion) H + = one proton (mostly) H + = one proton (mostly) when the atom loses its electron to become a hydrogen ion, all that remains is the nucleus when the atom loses its electron to become a hydrogen ion, all that remains is the nucleus thus, hydrogen ions are sometimes referred to as protons thus, hydrogen ions are sometimes referred to as protons therefore, any substance that yields a proton is an acid, or an acid is a proton donor therefore, any substance that yields a proton is an acid, or an acid is a proton donor

39 Copyright  2010 Scott A. Bowling. Acids and Bases bases are proton acceptors bases are proton acceptors a base is a substance that can accept a proton a base is a substance that can accept a proton

40 Copyright  2010 Scott A. Bowling. Acids and Bases bases are proton acceptors bases are proton acceptors a base is a substance that can accept a proton a base is a substance that can accept a proton bases either dissociate in water to produce hydroxide ions and a cation, or split water to form a cation and hydroxide ion: bases either dissociate in water to produce hydroxide ions and a cation, or split water to form a cation and hydroxide ion: NaOH Na + + OH - or B (a base) + HOH BH + + OH -

41 Copyright  2010 Scott A. Bowling. Acids and Bases water tends to slightly dissociate into hydrogen and hydroxide ions (H + and OH - ) water tends to slightly dissociate into hydrogen and hydroxide ions (H + and OH - ) HOH H + + OH -

42 Copyright  2010 Scott A. Bowling. Acids and Bases water tends to slightly dissociate into hydrogen and hydroxide ions (H + and OH - ) water tends to slightly dissociate into hydrogen and hydroxide ions (H + and OH - ) HOH H + + OH - in pure water, the concentrations of these ions are equal: in pure water, the concentrations of these ions are equal: [H + ] = [OH - ] = M (note that the designation M stands for molar, the moles of a substance per liter of solution) (note that the designation M stands for molar, the moles of a substance per liter of solution) the product of these remains constant: [H + ] x [OH - ] = the product of these remains constant: [H + ] x [OH - ] = acidic solutions have an elevated [H + ], and thus reduced [OH - ] acidic solutions have an elevated [H + ], and thus reduced [OH - ] basic solutions have an elevated [OH - ], and thus reduced [H + ] basic solutions have an elevated [OH - ], and thus reduced [H + ]

43 Copyright  2010 Scott A. Bowling. Define acids and bases.

44 Copyright  2010 Scott A. Bowling. What does pH stand for, and how does the pH scale work?

45 Copyright  2010 Scott A. Bowling. Acids and Bases pH scale shorthand notation for proton concentration of a solution pH scale shorthand notation for proton concentration of a solution the pH is -log[H + ] the pH is -log[H + ] pure water ( [H + ]= M ) has pH = 7 pure water ( [H + ]= M ) has pH = 7 pH 7 is basic pH 7 is basic pH of most living cells is usually ~ 7.2 to 7.4 pH of most living cells is usually ~ 7.2 to 7.4

46 Copyright  2010 Scott A. Bowling. What does pH stand for, and how does the pH scale work?

47 Copyright  2010 Scott A. Bowling. How do pH buffers work?

48 Copyright  2010 Scott A. Bowling. Acids and Bases buffers minimize pH changes buffers minimize pH changes weak acids and weak bases serve as buffers weak acids and weak bases serve as buffers living things use buffers to prevent dramatic changes in pH, which can kill them living things use buffers to prevent dramatic changes in pH, which can kill them

49 Copyright  2010 Scott A. Bowling. Acids and Bases buffers minimize pH changes buffers minimize pH changes weak acids and weak bases serve as buffers weak acids and weak bases serve as buffers living things use buffers to prevent dramatic changes in pH, which can kill them living things use buffers to prevent dramatic changes in pH, which can kill them

50 02.20 Buffer Formation Slide number: 2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. H2OH2O Water CO 2 Carbon dioxide +

51 02.20 Buffer Formation Slide number: 3 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. H 2 CO 3 Carbonic acid H2OH2O Water CO 2 Carbon dioxide +

52 02.20 Buffer Formation Slide number: 4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. H 2 CO 3 Carbonic acid H2OH2O Water CO 2 Carbon dioxide – HCO 3 – Bicarbonate ion H + Hydrogen ion

53 Fig. 2.19

54 Copyright  2010 Scott A. Bowling. How do pH buffers work?

55 Copyright  2010 Scott A. Bowling. Chapter 3: What’s so great about water? polar nature of water molecules polar nature of water molecules What properties of water are important for life? What properties of water are important for life? Acids and Bases Acids and Bases Some useful definitions Some useful definitions

56 Copyright  2010 Scott A. Bowling. Some useful definitions solvent – a liquid into which a substance dissolves solvent – a liquid into which a substance dissolves solute – the dissolved substance solute – the dissolved substance solution = solvent + solute solution = solvent + solute salts – form from acids and bases salts – form from acids and bases water is formed water is formed the cation of the base and the anion of the acid form the salt the cation of the base and the anion of the acid form the salt HCl + NaOH NaCl + HOH

57 Copyright  2010 Scott A. Bowling. Some useful definitions electrolytes are salts, acids, or bases that form ions in water and thus can conduct an electrical current when dissolved in water (pure water is a poor conductor of electricity, but put in a salt and it becomes an excellent conductor) electrolytes are salts, acids, or bases that form ions in water and thus can conduct an electrical current when dissolved in water (pure water is a poor conductor of electricity, but put in a salt and it becomes an excellent conductor) nonelectrolytes are substances like sugar that dissolve in water but do not become ionic nonelectrolytes are substances like sugar that dissolve in water but do not become ionic mixtures - a mixture of 2 or more elements and/or compounds; they can be broken down into elements and compounds by simple physical means. There are two types: mixtures - a mixture of 2 or more elements and/or compounds; they can be broken down into elements and compounds by simple physical means. There are two types: heterogeneous mixtures - mixtures that are not of uniform composition throughout - a living organism is a good example heterogeneous mixtures - mixtures that are not of uniform composition throughout - a living organism is a good example homogeneous mixtures - mixtures that are completely uniform throughout - a salt water solution is a good example homogeneous mixtures - mixtures that are completely uniform throughout - a salt water solution is a good example


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