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Chapter 3 WATER AND THE FITNESS OF THE ENVIRONMENT. Themes: Emergent Properties Structure and Function Science, Technology and Society. Objectives:. Polarity of water molecules Cohesion of water Water moderates temperature on Earth Ice floats… why? Solvent of life - PowerPoint PPT Presentation
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Chapter 3 WATER AND THE FITNESS OF THE ENVIRONMENT
Themes:
1. Emergent Properties
2. Structure and Function
3. Science, Technology and Society
Objectives:
• Polarity of water molecules
• Cohesion of water
• Water moderates temperature on Earth
• Ice floats… why?
• Solvent of life
• Organisms are sensitive to pH changes
• Acid Rain
Root Words:
• Kilo –
• Hydro –
• - philos
• - phobos
Hydrogen Bonding is the Most Important Concept: Most of water’s characteristics
are due to the principle of hydrogen bonding.•-
•+
•+
•+
•+
•Formation of hydrogen bonds -Formation of hydrogen bonds - Releases heatReleases heat
•Breaking of hydrogen bonds - Breaking of hydrogen bonds - Absorbs Absorbs heatheat
Cohesion - hydrogen bonds holding water molecules together, helps water move up a tree.
•Surface tension - cohesion
•Beading of water – cohesion
•Water’s high heat of evaporation is due Water’s high heat of evaporation is due to hydrogen bonding.to hydrogen bonding.
•Heat of Vaporization - quantity of heat a liquid must absorb for 1 gm of water to be converted from liquid to a gas.
•Specific heat - amt. of heat that must be absorbed or lost by 1gm. Of a substance to change it’s temp. 1° C. Water is 1cal/g/1°C.
• Water has high specific heat compared to other substances , thus it resists changes in temp. when it absorbs or releases heat.
• Water also has high boiling point.
•ICE - Water expands when it freezes. Ice is less dense than liquid water. WHY???
•NOTE - hydrogen bonding causing less H20/vol
A CRYSTAL OF TABLE SALT DISSOLVING IN WATER.
•The H+ regions of the polar water molecules are attracted to the chloride anions (green), the O- regions cling to the sodium cations (yellow). The sphere of water molecules surrounding a solute ion (or molecule) is called a hydration shell.
•HYDROPHILIC - “WATER LOVING” SUBSTANCES THAT HAVE AN AFFINITY FOR WATER EVEN IF THEY DO NOT DISSOLVE IN WATER. (IONIC OR POLAR MOLECULES).
•HYDROPHOBIC - “WATER FEARING” WILL NOT DISSOLVE IN WATER OR HAVE NO AFFINITY FOR WATER. (NON-IONIC, NONPOLAR SUBSTANCES)
CALORIES & KILOCALORIES:
Calories = amt. of heat needed to raise 1 gm. of water 1 ° C.
Kilocalorie = 1000 calories.If 10 ml of water was raised 1
° C this would be 10 calories.
MAKING AQUEOUS SOLUTIONS:
To make a solution - dissolve solute in small amt. of water THEN add water to get the final volume.A mole is = in number to mol. weight of a substance in grams.
Molecular weight = sum of weights of all atoms in a molecule.
EXAMPLE - C2H5O2NH2
mol. Wt. : H =7; O = 32; N= 14; C = 24 (77)
•MOLARITY - # of moles of solute per liter of solution.
•77 g of solute in 1 liter of water = 1 M solution.
•7.7 g of solute in 1 liter of water = 0.1 M solution.•REMEMBER - you are attempting to keep the same proportion of solute to solvent in the solution.
•ACIDS, BASES & BUFFERS:
•ACIDS: H+ (proton) donors in aqueous solution (increase H+ ions in solution.)
•BASE : H+ (proton) acceptor in aqueous solution (reduces in H+ ions in solution.). Also reduce H+ ions indirectly by dissociating to form OH- ions (combine with H+ to form H2O).
•Aqueous - of, like, or containing water; watery
•pH Scale:pH Scale: -log [H] & is a ten fold difference between whole #’s.
•EXAMPLE: pH 6 to pH 5 = 10 times increase in acidity.
•EXAMPLE: pH 6 to 4 = 100 times increase in acidity.
•0 1 2 3 4 5 6
•(Strong acid) (med. acid) (weak acid)
•pH ScalepH Scale - [H - [H++] [OH] [OH--] = 10 ] = 10 --
1414
•pH 7 [HpH 7 [H++]]-7-7 [OH] [OH]-7 -7 = 10 = 10-14-14
•pH 6 [HpH 6 [H++]]-6-6 [OH] [OH]-8 -8 = 10= 10-14-14
•Common acids - lemon juice, vinegar, coffee.
•Common bases - seawater(pH8) ammonia, bleach.
•DO ALL SUBSTANCES HAVE MEASURABLE pH?
•NO !!!!! Why???
•Substance must dissolve in water (dissociate in water).
•EXAMPLES: Hydrocarbons which are nonpolar - gasoline, kerosene, butane, methane.
•BUFFERS: Chemicals that minimize changes in pH by:
•Accepting H+ OR release H+ ions
•(acid solution) ( basic solution) •NOTE: Bases are also
called alkaline.
•Even a molecule as large as a protein can dissolve in water if it has enough ionic and polar regions on its surface. The mass of purple here represents a single such molecule,which water molecules are surrounding.
•WATER-WATER-SOLUBLE SOLUBLE PROTEINPROTEIN