WATER PROPERTIES
Supplemental Textbook MaterialCh. 16, p. 349-361
Be sure to attend lab this week
• Bring the lab manual• Must pass lab to pass this class• Instructors will give percent lab grade to
one another
Covalent Bonds
• Need ‘octet’ of electrons surrounding element in the ‘dot diagram’
• Some bonds are multiple, stronger!
Covalent Bond—Chlorine Gas
• Covalent bond• Draw dot diagram
for each atom• Bond using all
electrons• Octet around each• Show bonding pair
with a line
Octet Rule for Oxygen
• Start with dot diagram
• Don’t have octets of electrons
• Share two pairs to get to eight for each atom
• Indicate with double bar
Naming Compounds
• Find subscripts to indicate how many of each atom in the molecule
• Use chart at right for number of each
Polar molecules
Electro-negativity
Poly-atomic ions
• Covalently bonded compounds• Not electrically neutral• Maintain covalent bonds within ions as
they interact with other ions to form ionic compounds
• Those bonded to oxygen become ‘–ate’
Common poly-atomic ions
• Hydroxide OH-
• Bicarbonate HCO3-
• Carbonate CO32-
• Sulfate SO42-
• Nitrate NO3-
• Phosphate PO43-
• Chromate CrO42-
Chemical Formulas
Molecule has specific ratio of elements• Subscripts—how many• Parentheses—how many sets• Coefficients—how many molecules in
reaction
Chemical Formulas• H2SO4
• Ca3(PO4)2
• Na2O + CaCl2 → CaO + 2 NaCl• MgBr2 + 2Ag(NO3) → Mg(NO3)2 + 2AgBr
Predict Molecule Shape
• Draw molecule dot diagram• Put most electronegative element in the
center of molecule
Electro-negativity
Predict Molecule Shape
• Draw molecule dot diagram• Put most electronegative element in the
center of molecule• Arrange other atoms around it• Include all unbonded pairs and bonds, so
that each atom has ‘octet’ of electrons• Choose tentative shape from number of
atoms plus unbonded pairs
Predict Molecule Shape
• Choose tentative shape from number of atoms plus unbonded pairs
• Erase unbonded pairs• Adjust shape to account for the empty
spots– Tetrahedrons may become pyramids– 3-d shapes may become bent
Geometry of Molecules
Typical Shapes of Molecules
Tetrahedral molecules
Pyramidal molecules
Bent molecules
Polar molecules
Dipole attraction in solid and liquid
Dissolution of ionic substance
Solute/Solvent
Water phases and molecules
Water Molecule
• Bent • Covalent bonds• Polar• Dissolves ionic
substances
Properties of Water
• Solid water floats on liquid water• High specific heat• High heat of vaporization• ‘Universal’ solvent
Distribution/Cycle Animation
Hydrologic Cycle
Natural substances in water
Impurities in Runoff
• Atmosphere• Dissolved substances• Silt, etc.• Radon
Organic byproducts in water
Contamination of Water• Micro-organisms• Decay products• Plant nutrients• Petroleum compounds• Acid• Industry• Mining
Drinking water standards
Be sure to attend lab this week
• Bring the lab manual• Must pass lab to pass this class• Instructors will give percent lab grade to
one another
Heat and Energy Transfer
Supplementary Textbook MaterialChapter 18: p. 410-420
Review Questions: 2-4, 21-26
Water Drop
http://www.wested.org/pblnet/exp_projects/H2O.html
Impurities in Runoff
• Atmosphere• Dissolved substances• Silt, etc.• Radon
Organic byproducts in water
Pollution Sources
Contamination of Water• Micro-organisms• Decay products• Plant nutrients• Petroleum compounds• Acid• Industry• Mining
Raw Sewage discharge
http://www.nwri.ca/sande/nov_dec_2002-e.html
Plant nutrient pollution
http://www.na.fs.fed.us/SPFO/pubs/n_resource/riparianforests/Tab%20I.htm
Agricultural Runoff
http://www.na.fs.fed.us/SPFO/pubs/n_resource/riparianforests/Tab%20I.htm
Oil pollution
http://www.intertanko.com/tankerfacts/sizes/pollution.htm
Mine leachate
http://www.ew.govt.nz/enviroinfo/hscs/contam/
Water Pollution
http://www.jvkco.com/digidare/water.html
Water Pollution Prevention
http://www.jvkco.com/digidare/water.html
Drinking water standards
Temperature• Quantity of hotness• Celsius
0o freezing point of pure water at standard pressure100o boiling point at standard pressure
• Fahrenheit0o was lowest attained32 was his age when he performed experiments212 is boiling point in those increments
Temperature
• Convert with equationsOrder of operations
Parentheses firstThen multiply or divideAdd or subtract last
• Or use adjacent scales such as in the appendix of Earth Science textbook (p. 683)
32)-(F95C =
32 C59F +=
Temperature• Kelvin same size as degree Celsius• ‘Absolute Zero’ is 0 K
(notice no degree symbol on K)• 0o C = 273 K• Equation for Prelab exercise 2 has error
K – 273 = Co (change + to - )
Heat
• Calorie– Amount of heat required to raise the
temperature of 1 mL pure water 1o C– Food ‘Calories’ are kilocalories
• Joule ~ ¼ of calorie– 1 cal. = 4.184 J
Specific Heat Capacity
• Quantity of heat needed to change the temperature of given amount of a substance 1o C
• Water—very high specific heat capacity– Maritime areas more mild temperature than
continental areas
Heat Expansion
• Random motion causes substance to be bigger
• Liquids usually have greater heat expansion than solids
• Thermostats use different expansion of different type of metals
Water Expansion
• Unusual response to cooling• Contracts until reaching 4o C• Expands slightly upon further cooling to 0o C• Expands 9% upon freezing
Water Molecule
• Bent • Polar
Water Expansion
• Molecule shape fit together closer in liquid• Open structured crystal due to hydrogen
bonding of polar molecules upon freezing
Water Expansion
http://www.elmhurst.edu/~chm/vchembook/122densityice.html
Heat of Water
Supplementary Textbook MaterialsChapter 19
Pages 424-435
Electron Structure Diagrams
• Two ways to correctly do these– With elemental
symbol in center– With number of
protons in center• Not with circles
around symbol and electrons distributed around circle
Dot Diagrams
• Only show VALENCE Electrons
• Don’t show shells
Phases of Matter• Solid• Liquid• Gaseous or vapor• Plasma
Gas, Liquid, and Solid
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 441
Gas Liquid Solid
http://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP_files/frame.htm
Evaporation
• Kinetic energy of molecules• Taken from liquid—cools it• Gaseous phase or vapor phase
Gas Steam
H2O(g) Steam
http://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP_files/frame.htm
Water vapor
http://en.wikipedia.org/wiki/Water_vapor
Evaporation or Not
http://www.geology.sdsu.edu/classes/geol351/01watercycle/watercyclefigs.htm
Condensation
• Opposite of evaporation• Kinetic energy of molecules• Heats environment
Liquid Water
H2O(l) Water
http://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP_files/frame.htm
Condensation on Glass
http://www.geology.sdsu.edu/classes/geol351/01watercycle/watercyclefigs.htm
Atmosphere
• Evaporation – Energy goes into air– Cools remaining water
• Condensation– Energy goes from air to surface– Warms local environment
Atmosphere
• Warm air has greater capacity for holding water in the vapor phase
• Saturation = at capacity• Relative Humidity—percent of water
contained compared to saturated amount at that temperature
Water Vapor Capacity
http://www.wdtv.com/weather/images/Weather_Review/humidity.htm
Condensation
http://observe.arc.nasa.gov/nasa/earth/hydrocycle/graphics/condensation.jpg
Condensation diagram
http://weatherstreet.com/weatherquestions/What_is_condensation.htm
Sea Fog
http://www.anythingmarine.co.uk/anything/met.htm
Boiling
http://www.chem.purdue.edu/gchelp/liquids/boil2.html
Boiling
http://www.deepseaimages.com/dsilibrary/showphoto.php?photo=2912&password=&sort=1&size=medium&cat=853&page=1
Microscopic boiling
http://www.chem.purdue.edu/gchelp/liquids/boil2.html
Pressure Cooker
http://www.goodmans.net/get_item_ma-6qt_maitres-806212-6-qt-cooker.htm
Pressure canner
http://hgic.clemson.edu/factsheets/HGIC3020.htm
Boiling Temp vs.Pressure
http://www.chem.purdue.edu/gchelp/liquids/boil2.html
Boiling at less than 100 o C
• Reduce Pressure
http://www.micrecol.de/air2.html
Energy of Water Phase Change
• Calorie: energy to change 1 gram of water 1 K or 1 oC
• Also need energy to change to different state of matter
• Energy of vaporization/condensation540 calories per gram of water
• Energy of melting/freezing80 calories per gram
solid
liquid
gasvaporization
condensation
melting
freezing
Heat added
Tem
pera
ture
(o C)
AB
C
DE
Heating Curve for Water
0
100
LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 487
http://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP_files/frame.htm
Solid Ice
H2O(s) Ice
http://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP_files/frame.htm
Molecular Structure of Ice
Hydrogen bonding
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 455
http://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP files/frame.htm
Solid, Liquid, Gas
(a) Particles in solid (b) Particles in liquid (c) Particles in gas
http://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP_files/frame.htm