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