Physical Properties Of Water-bilal Ahmad Sajid

Assignment on

PHYSICAL PROPERTIES OF WATER

BY

BILAL AHMAD SAJID M.Phil/PhD-1st semester Session: 2009 Submitted To:

Dr. M.RIAZ Centre of Excellence in Geology

DEPARTMENT OF ENVIRONMENTAL

SCIENCES UNIVERSITYOF PESHAWAR

ACKNOWLEDGEMENT Fist of all, greatness, sanctity and glory to Almighty ALLAH, who blessed me to complete my assignment. I will acknowledge prays and love of my parents which enabled me to complete my assignment. I will also acknowledge the assistance, guidance and continuous feed back from Mr. Muhammad Riaz professor in Centre of Excellence in Geology University of Peshawar. It has been pleasure learning from all my class fellows. I will be very thankful to the librarian in Centre of Excellence in Geology who provided me book in time. I am grateful & thankful to The University of Peshawar which provided me a platform for learning and brightening my future.

BILAL AHMAD SAJID

SUMMERY 1

Water is a cosmopolitan substance with its peculiar properties which are supporting all forms of life on earth. It is colorless, odorless and tasteless and can be found in all three states of matter i.e. solid (ice), liquid (water) and gas (vapor). It is responsible for the phenomenon of evapotranspiration, condensation and precipitation. It’s freezing and thaw and hydraulic action causes weathering of rocks and erosion. Its property of thermal expansion is a source of geothermal hydropower energy from under the earth. It has maximum density at 4C and below it on freezing it increases in volume by 9% and floats on water. This maintains a constant temperature of 4C in the water below ice sheets and as a result maintain life in water.

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Table of Contents

Acknowledgement..................................................................................................i

Summery...............................................................................................................ii

1.

INTRODUCTION................................................................................................1

2.

OBJECTIVES.....................................................................................................1

3.

WATER.............................................................................................................1

4.

IMPORTANCE OF WATER..................................................................................2

5.

PHYSICAL PROPERTIES OF WATER...................................................................3

5.1.

Color of Water...........................................................................................3

5.2.

Taste and Odor.........................................................................................4

5.3.

Cohesive & adhesive forces......................................................................5

5.3.1.

Surface Tension..................................................................................5

5.3.2.

Capillary action...................................................................................5

5.4.

Viscosity....................................................................................................5

5.6.

Density......................................................................................................6

5.7.

Vapor pressure..........................................................................................7

5.8.

Response to Temperature.........................................................................7

5.8.1.

Freezing..............................................................................................7

5.8.2.

Thermal expansion.............................................................................8

5.9.

Hydraulic Action of Water.......................................................................10

5.9.1.

Water erosion...................................................................................10

5.10.

Specific heat capacity and heat of vaporization...................................11

5.11.

Evaporation and Transpiration.............................................................11

5.12.

Atmospheric Humidity, dew point and frost point................................12

5.13.

Clouds formation and precipitation......................................................13

6.

Conclusion.....................................................................................................14

BIBLIOGRAPHY.....................................................................................................15

Books................................................................................................................15

DVD Source......................................................................................................15

Online Source...................................................................................................15

Figures……………………………………………………………………………………………… …………………………………………16

Online Source

LIST OF FIGURES & TABLES Figures Page # Figure 1: Distribution of Earth's Water………………………………………………...

2

Figure 2: Drop of Water………………………………………………………………………

3

Figure 3: Geyser……………………………………………………………………… …………

8

Figure 4: Fumarole………………………………………………………………… …………..

8

Figure 3: Geothermal Power Plant………………………………………………………

9

Figure 6: Splash Erosion……………………………………………………………………..

10

Figure 7: Sheet Erosion…………………………………………………………………… …

10

Figure 4: Gully Erosion…………………………………………………………………… ….

11

Figure 5: Illustrates the concept of relative humidity………………………….

12

Tables Page # Table 1: Density of Water Molecules at various…………………………………..

6

Table 1: Temperature vs. Vapor Pressure of Water…………………………….

7

1.

INTRODUCTION

I have voluntarily selected this topic as an assignment in which I have tried to explain in detail, although not all but maximum physical properties of water. Water is a common but peculiar substance possessing many strange properties which are supporting all forms of life on earth. Color, odor & taste, density i.e. floating of ice on water, response to temperature and pressure i.e. thermal expansion (geysers, fumaroles and hot springs are source of geothermal energy), and precipitation are some of the physical properties of water which I have included in this topic.

2.

OBJECTIVES

My major objectives of taking this assignment are 2.1.

To understand clearly and in some detail, the physical properties of water.

2.2.

To accept maximum responsibility, to know maximum, to explore maximum

and to utilize my talent fully by searching libraries and internet. 2.30

To build up my confidence by presenting this assignment in front of my class

fellows.

3.

WATER

Water is an omnipresent chemical substance, composed of hydrogen and oxygen, that is essential for the survival of many known forms of life. At 1 atmospheric pressure it has a boiling point of 100C and freezing point of 0C. Its density is 1cc at room temperature while has maximum density at 4C1. In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and gaseous state, water vapor or steam. Water covers 71% of the Earth's surface. On Earth, it is found mostly in oceans and other large water bodies, with 1.6% of water below ground in aquifers and 0.001% in the air as vapor, clouds (formed of solid and liquid water particles suspended in air), and precipitation. Saltwater oceans hold 97% of surface water, glaciers and polar ice caps 2.4%, and other land surface water such as rivers, lakes and ponds 0.6%. A very small amount of the Earth's water is contained within biological bodies and manufactured products. Other water is trapped in ice caps, glaciers, aquifers, or in lakes, sometimes providing fresh water for life on land2. 1 "Water." Microsoft® Encarta® 2009 [DVD]. Redmond, WA: Microsoft Corporation, 2008. 2 Water. (2009, July 31). In Wikipedia, The Free Encyclopedia. Retrieved July 31, 2009, from http://en.wikipedia.org/w/index.php?title=Water&oldid=305251617

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Figure 6: Distribution of Earth's Water Source: http://upload.wikimedia.org/wikipedia/commons/7/74/ Earth's_water_distribution.gif

4.

IMPORTANCE OF WATER

Water is very unusual substance wit many strange and unique properties that are so important to life on planet earth that without it, it would be almost impossible for the life to exist. How does this simple molecule, composed of two hydrogen atoms and one oxygen atom, behave the way it does and how does it support life? Some important familiar properties of water are: 4.1

It is colorless

4.2

It is odorless

4.3

It is tasteless

4.4

It feels wet

4.5

It dissolves nearly everything

4.6

It exists in three forms: liquid, solid, gas, ad is cycled through the water cycle

4.7

It can absorb a large amount of heat

4.8

It sticks together into beads or drops3

4.9

It flows and erodes the surface of earth: it moves sediments to form beaches,

river banks and bars

3 Manahan, S. E. (1995). Environmental Chemistry. 6th edition, Private Company, Headquarters Location 6000 Broken Sound Pkwy. NW, Ste. 300, Boca Raton, FL 33487, United States, pp-27

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4.10

It shapes lipid and protein molecules and give them their 3 dimensional form

which is critical to their function. 4.11

It is part of every living organism on the planet earth4

Water is a very strong solvent and is often referred to as the universal solvent. Substances that dissolve in water, e.g. salts, sugars, acids, alkalis, and some gases – especially oxygen, carbon dioxide (carbonation) – are known as "hydrophilic" (water-loving) substances. All the major components in cells (proteins, DNA and polysaccharides) are also dissolved in water. Through Capillary action water moves up a narrow tube against the force of gravity. This property is relied upon by all vascular plants, such as trees. Water moves continually through a cycle of evapotranspiration, precipitation and runoff, usually reaching the sea5.

5.

PHYSICAL PROPERTIES OF WATER

5.1. Color of Water Pure water is colorless but is often colored by many foreign substances. The color of water and ice is, intrinsically, a very light blue hue, although water appears colorless in small quantities. Ice also appears colorless, and water vapor is essentially invisible as a gas. Water is transparent, and thus aquatic plants can live within the water because sunlight can reach them. The color due to suspended substances is temporary and can be removed if those substances are removed. The color due to dissolved substances is known as true color and can not be removed by ordinary

Figure 7: Drop of Water Source: http://weblogs.newsday.com/news/local /longisland/politics/blog/water.jpg

methods. After contacting with organic debris such as leaves, weeds or wood, water takes on yellowish-brown hues. Iron oxide cause reddish water color and manganese oxides cause brown or blackish water. Industrial wastes from textile and dyeing operations, pulp and paper production, food processing, chemical production, mining, refining and slaughterhouse operations may also add significant coloration to the water in receiving streams. 4 Physical Properties of Water. (2008). Planet Water.au.com. Retrieved 28 July, 2009 from http://www.ozh2o.com/h2phys.html 5 Water. (2009, July 31). Opt Cit.

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Colored water is not aesthetically accepted to the general public. Highly colored water is unsuitable for laundering, dyeing, paper making, beverages, dairy production and other food processing, and textile and plastic production. Thus the color of water affects its value both for domestic and industrial use. Some organic compounds causing true color may exert chlorine demand and reduce the effectiveness of chlorine as a disinfectant. Most important are the product formed by the combination of chlorine with some color producing organics. Phenolic compounds, common constituents of vegetative decay products, produce very objectionable taste and odor compounds with chlorine. Additionally some compounds of naturally occurring organic acids and chlorine are known to be carcinogens6.

5.2. Taste and Odor Water can dissolve many different substances, giving it varying tastes and odors. Substances that produce an odor in water will also impart a taste as well. But there are many substances which produce taste but no odor. Taste and odor producing substances include minerals, metals and salts from soil, end products from biological reactions, and constituents of wastewater. Inorganic substances are more likely to produce taste without any odor7. Alkaline materials and metallic salts may give a bitter and salty taste to water. Organic material on the other hand, is likely to produce both taste and odor. Biological decomposition of organics may also cause taste and odor producing liquids and gases in water. The most important among these are the reduced products of sulfur that impart a “rotten egg” taste and odor. The combination of two or more such substances neither of which would produce taste and odor individually may sometimes result in taste and odor problems. In fact, humans and other animals have developed senses which are, to a degree, able to evaluate the potability of water, avoiding water that is too salty or putrid. Humans also tend to prefer cold water to lukewarm water; cold water is likely to contain fewer microbes. The taste advertised in spring water or mineral water derives from the minerals dissolved in it, as pure H2O is tasteless and odorless. As such, purity in spring and mineral water refers to absence of toxins, pollutants, and microbes8.

6 Peavey,H., Rowe,D., & Tchobanoglous,G.(1985). Environmental Engineering. Mc Graw Hill Inc Longon. Pp. 18-17. 7 Water (properties). (2009, July 29). In Wikipedia, The Free Encyclopedia. Retrieved July 29, 2009, from http://en.wikipedia.org/w/index.php?title=Water_(properties)&oldid=304967583 8 Peavey,H. Rowe,D. Tchobanoglous,G.(1985). Opt Cit. Pp 20-21.

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5.3. Cohesive & adhesive forces Water has high force of cohesion and adhesion. The forces of attraction among the particles of liquid are called cohesive forces or cohesion. For example surface is due to cohesion. The force of attraction between a liquid and another surface is called adhesive force or adhesion. For example, attraction between water molecules and particles of glass is called adhesion9. 5.3.1.Surface Tension

Water has a high surface tension. This is the ability of a substance to stick to itself. The sticking together or the cohesive property of water is due to hydrogen bonding. The molecules at the surface are attracted by many molecules from below it but not from above. The molecules at the surface, therefore feel a net attraction inward. This attraction creates surface tension. Surface tension of water decreases with increase in temperature because increased kinetic energy of the molecules decreases the effect hydrogen bonding. Detergents also reduce the surface tension of water by breaking up hydrogen bonding10. 5.3.2.Capillary action

The rise of liquid in a small capillary tube is called capillary action. Capillary action is due to strong adhesion of water molecule with surface of the tube. Cotton and paper absorb water by capillary action. Water rises in narrow channels of these materials. It is the capillary action which causes rise of water from the soil to plants11. The significance of this capillary action is that rock and soil pores tend to act like capillary tube. If a soil or rock is wet a positive force or pressure must be applied to extract water from it but if applied pressure is less than capillary force then you can not extract water from it12.

5.4. Viscosity Water has the ability to flow because its molecules can slide over each other. The resistance of liquid to its flow is called viscosity. The viscosity of water is due to internal friction among different layers of molecules. Liquids which flow very slowly like honey or glycerin have high viscosities as compared to water. Viscosity of water depends upon temperature and density. Higher the temperature the lower will be the viscosity and higher the density the 9 Chaudhry, R. A. et al. (1993). Text Book of Chemistry. F.Sc Part 1. Peshawar: NWFP Text Book Board. Pp. 70-90. 10 Ibid. 11 Ibid. 12 Deming, D. (2002). Introduction to Hydrogeology. Mc Graw Hill Inc, New York: pp.143-145.

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higher will be the viscosity and vice versa. The viscosity of water is taken as 1 centipoises at 25C13.

5.6. Density Density is defined as objects mass per unit volume d= m/v. At 4°C pure water has a density (weight or mass) of about 1 g/cu.cm or 1 g/ml or 1 kg/liter. When water freezes it expands rapidly adding about 9 % by volume. Fresh water has a maximum density at around 4° Celsius14.

Water

is

the

only

substance where the maximum density does not occur when solidified.

This

results

in

an

unusual phenomenon: water's solid form, ice, floats upon water, allowing organisms to survive

Temperature (degre es Celsius) 0 (solid) 0 (liquid) 4 20 40 60 80 100 (gas)

Density (grams per cubic centimeter) 0.9150 0.9999 1.0000 0.9982 0.9922 0.9832 0.9718 0.0006

Table 1: Density of Water Molecules at various Temperatures Source: http://www.physicalgeography.net/fundamentals/ 8a.html

inside a partially-frozen water body because the water on the bottom has a temperature of around 4 °C15.

5.7. Vapor pressure It is the pressure exerted by vapors in equilibrium with its pure liquid at a given temperature. It means that in a closed the pressure exerted by water vapors will be equal to the pressure exerted by pure water. This vapor pressure increases with temperature16.

13 Chaudhry, R. A. et al. (1993). Opt Cit. 14 Density Specific Weight Gravity. (2008). The Engineering Toolbox. Retrieved 28 July, 2009 from http://www.engineeringtoolbox.com/density-specific-weight-gravity_290.html 15 Physical Properties of Water. (2008). SiMetric. Retrieved 28 July, 2009 from http://www.simetric.co.uk/si_water.htm 16 Chaudhry, R. A. et al. (1993). Opt Cit.

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Temperature ( C )

Vapor Pressure (mm of Hg)

0

5

20

18

40

55

60

149

80

355

100

760

120

1489

Table 2: Temperature vs. Vapor Pressure of Water Source: Text Book of Chemistry

5.8. Response to Temperature 5.8.1.Freezing

Water is the chief agent of weathering, both chemical and mechanical. The mechanical weathering results in disintegration of rocks & is due to frost. It occurs in colder and temperate climates where rocks get soaked with rain water, which is frozen into ice at night. During the day it again melts. On being frozen its volume increases by 9% and the result is that cracks and fissures are formed in the rocks, which finally breaks into blocks along lines of weakness17. 5.8.2.Thermal expansion

Water expands on heating from 4C to onwards. On reaching the temperature of 100C it boils and starts converting to vapors. This phenomenon is responsible for the formation of geysers, hot springs and fumaroles in volcanic areas of the world. Geysers are caused when underground chambers of water are heated to the boiling point by volcanic rock.

17 Gupta, D. A., & Kapoor, N. A. (1991). Principles of Physical Geography. 9th edition. New Delhi: S.Chand & Company Ltd. Pp. 279. Figure 3: Geyser Source: http://www.aroundhere.ca/Gallery/OldFaithful-Geyser-Yellowstone.jpg

Figure 4: Fumarole Source: 2 http://upload.wikimedia.org/wikipedia/ commons/4/49/Steam_Phase_eruption _of_Castle_geyser_with_double_rainbo w.jpg

When heat causes the water to boil, pressure forces a superheated column of steam and water to the surface. The initial amount of water released at the surface lessens the column’s weight, which also lowers its boiling point. When the boiling point drops, the entire column of water vaporizes at once, shooting out of the ground in a spectacular eruption. Fumaroles are similar to geysers, but release bursts of hot gases instead of water. Hot springs are supplied by the same sources as geysers, but these systems are under lower pressure, which causes water to bubble and pool at the surface instead of erupting18. These geysers, hot springs and fumaroles are most easily exploited sources of geothermal energy. Geothermal energy is a renewable energy source because the water is replenished by rainfall and the heat is continuously produced inside the earth. This pressurized water and steam is used to produce electricity by the use of turbine19.

18 “Geyser.” Microsoft® Encarta® 2009 [DVD]. Redmond, WA: Microsoft Corporation, 2008. 19 “ Geothermal Energy, Energy from the Earth's Core” (2009). Energy Information Administration, Official Energy Statistics from U.S Government. Retrieved 26 July, 2009 from http://www.eia.doe.gov/kids/energyfacts/sources/renewable/geothermal.html

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Figure 8: Geothermal Power Plant Source: http://alternateformsofenergy.com/Geothermal/images/How-aGeothermal-Power-Plant-Works_clip_image003.gif

Geothermal plants are in operation in Italy, New Zealand, Japan, Iceland, Mexico and the United States etc.

Geothermal plant does not use fuel for power generation so is

producing less pollution20.

20 Namzer, Marilyn Levin, Carter, Anna, and Nemzer, Kenneth Press. (2008). “Geothermal Energy” Microsoft® Encarta® 2009 [DVD]. Redmond, WA: Microsoft Corporation.

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5.9. Hydraulic Action of Water 5.9.1.Water erosion

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Figure 6: Splash Erosion http://www.vbco.org/media/planningeduc /tn_raindrp.jpg

Figure 7: Sheet Erosion Source: http://image61.webshots.com/161/ 5/98/41/540559841ZonHRJ_fs.jpg

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Figure 7: Sheet Erosion Source: http://image61.webshots.com/161/ 5/98/41/540559841ZonHRJ_fs.jpg

Erosion is the detachment of earth material from the surface. Once detached, agents like water or wind transport the material to a new location where it is deposited. The most important form of erosion is that done by water. Heavy rain and running water are the chief agents of erosion. Heavy rain hits the soil like hammer, removing and carrying the upper loose soil particle while simultaneously filling the pores in next layer of soil and compact it reducing the infiltration. As the infiltration reduces surface runoff starts often starting sheet erosion. Running water carry this eroded material and on the way grinds the material into finer particles as well as cutting the surface over which it is being transported and deposits it at certain places in the form of layers or strata forming stratified or sedimentary rocks21.

21 “Erosion” Microsoft® Encarta® 2009 [DVD]. Redmond, WA: Microsoft Corporation, 2008.

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Figure 9: Gully Erosion Source: http://lh4.ggpht.com/_8WHwy0YGBc/RrcYj6aN7mI/AAAAAAAAAF8/kom7uqAQybM/P1 110630.JPG

5.10.

Specific heat capacity and heat of vaporization

Specific heat capacity of water is 4184 J /Kg at 0C temperature and 1 atmospheric pressure and is defined as the amount of heat energy necessary to raise the temperature of known mass of water by one degree Celsius. Water has the second highest specific heat capacity of any known substance, after ammonia, as well as a high heat of vaporization , both of which are a result of the extensive hydrogen bonding between its molecules. These two unusual properties allow water to moderate Earth's climate by buffering large fluctuations in temperature. The heat of vaporization of water is 2.26x106 J/Kg and is defined as the amount of heat required to convert one mole of water into vapors at the same temperature. It is due to this large value of heat of vaporization that steam produces more severe burns than does boiling water22.

5.11.

Evaporation and Transpiration

Water is removed from the surface of the Earth to the atmosphere by two distinct mechanisms: evaporation and transpiration.

22 David Deming (2002). Opt Cit. pp.109-111.

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Evaporation can be defined as the process where liquid water is transformed into a gaseous state. Evaporation can only occur when water is available. It also requires that the humidity of the atmosphere be less than the evaporating surface (at 100% relative humidity there is no more evaporation). The evaporation process requires large amounts of energy. For example, the evaporation of one gram of water requires 600 calories of heat energy. Transpiration is the process of water loss from plants through stomata. It is often difficult to distinguish between evaporation and transpiration. So we use a composite term evapotranspiration23.

5.12.

Atmospheric Humidity, dew point and frost point

The term humidity describes the fact that the atmosphere can contain water vapor. The amount of humidity found in air varies because of a number of factors. Two important factors are evaporation and condensation. At the water/atmosphere interface over our planet's oceans large amounts of liquid water are evaporated into atmospheric water vapor. This process is mainly caused by absorption of solar radiation and the subsequent generation of heat at the ocean's surface. In our atmosphere, water vapor is converted back into liquid form when air masses lose heat energy and cool24.

This is

Figure 10: Illustrates the concept of relative humidity Source: http://www.physicalgeography.net/fundamentals/8c.html

process

responsible for the development of most clouds and also produces the rain that falls to the 23 Pidwirny, M. (2006). "Evaporation and Transpiration". Fundamentals of Physical Geography, 2nd Edition. Retrieved 28 July, 2009 from http://www.physicalgeography.net/fundamentals/8i.html 24 Pidwirny, M. (2006). "Atmospheric Humidity". Fundamentals of Physical Geography, 2nd Edition. Retrieved 27 July, 2009 from http://www.physicalgeography.net/fundamentals/8c.html

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Earth's surface. The most commonly used measure of humidity is relative humidity. Relative humidity can be simply defined as the amount of water in the air relative to the saturation amount the air can hold at a given temperature multiplied by 100. Air with a relative humidity of 50% contains a half of the water vapor it could hold at a particular temperature. Associated with relative humidity is dew point (if the dew point is below freezing, it is referred to as the frost point). Dew point is the temperature at which water vapor saturates from an air mass into liquid or solid usually forming rain, snow, frost, or dew. Dew point normally occurs when a mass of air has a relative humidity of 100%. This happens in the atmosphere as a result of cooling through a number of different processes25.

5.13.

Clouds formation and precipitation

Condensation or deposition of water above the Earth's surface creates clouds. In general, clouds develop in any air mass that becomes saturated (relative humidity becomes 100%)26. Water is available on the Earth in the following three forms: vapor; liquid; and solid. In the atmosphere, three processes act to create water droplets or ice crystals. These three processes are: Condensation - water moving from a vapor to a liquid state. Freezing - water moving from a liquid to a solid state. Deposition - water moving from a vapor to a solid state. The formation of water droplets and ice crystals takes place when the water in the atmosphere is cooled. As air containing water vapor cools, the relative humidity of the air parcel increases until the dew or frost point is reached. At dew point (relative humidity = 100%) water begins to condense into droplets. If 100% relative humidity is reached below 0° Celsius deposition occurs and ice crystals form27.

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Conclusion

Water is of great importance and it is due to its peculiar physical properties. This discussion lead us to conclude that water is colorless, odorless and tasteless substance occurring 25 Ibid. 26 Pidwirny, M. (2006). “Condensation, Freezing, and Deposition”. Fundamentals of Physical Geography, 2nd edition. Retrieved 25 July, 2009 from http://www.physicalgeography.net/fundamentals/8d.html 27 Ibid.

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everywhere on earth in all three forms i.e. solid, liquid and gas,. It has a positive role in modifying weather by the process of cloud formation and precipitation. It is also a source of geothermal energy. Without water there will be no life on earth.

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BIBLIOGRAPHY Books Chaudhry, R. A. et al. (1993). Text Book of Chemistry. F.Sc Part 1. Peshawar: NWFP Text Book Board. Deming, D. (2002). Introduction to Hydrogeology. New York: Mc Graw Hill Inc. Gupta, D. A., & Kapoor, N. A. (1991). Principles of Physical Geography. 9th edition. New Delhi: S.Chand & Company Ltd. Manahan, S. E. (1995). Environmental Chemistry. 6th edition. Boca Raton: Private Company. Peavey,H., Rowe,D., & Tchobanoglous,G.(1985). Environmental Engineering. London: McGraw Hill Inc.

DVD Source Erosion. Microsoft® Encarta® 2009 [DVD]. Redmond, WA: Microsoft Corporation, 2008. Geyser. Microsoft® Encarta® 2009 [DVD]. Redmond, WA: Microsoft Corporation, 2008. Namzer, Marilyn Levin, Carter, Anna, and Nemzer, Kenneth Press. (2008). “Geothermal Energy” Microsoft® Encarta® 2009 [DVD]. Redmond, WA: Microsoft Corporation. Water. Microsoft® Encarta® 2009 [DVD]. Redmond, WA: Microsoft Corporation, 2008.

Online Source Density Specific Weight Gravity. (2008). The Engineering Toolbox. Retrieved 28 July, 2009 from http://www.engineeringtoolbox.com/density-specific-weight-gravity_290.html Geothermal Energy, Energy from the Earth's Core. (2009). Energy Information Administration, Official Energy Statistics from U.S Government. Retrieved 26 July, 2009 from http://www.eia.doe.gov/kids/energyfacts/sources/renewable/geothermal.html Physical Properties of Water. (2008). Planet Water.au.com. Retrieved 28 July, 2009 from http://www.ozh2o.com/h2phys.html 3

Physical Properties of Water. (2008). SiMetric. Retrieved 28 July, 2009 from http://www.simetric.co.uk/si_water.htm Pidwirny, M. (2006). “Condensation, Freezing, and Deposition”. Fundamentals of Physical Geography, 2nd edition. Retrieved 25 July, 2009 from http://www.physicalgeography.net/fundamentals/8d.html Water (properties). (2009, July 29). In Wikipedia, The Free Encyclopedia. Retrieved July 29, 2009, from http://en.wikipedia.org/w/index.php?title=Water_(properties)&oldid=304967583 Water. (2009, July 31). In Wikipedia, The Free Encyclopedia. Retrieved July 31, 2009, from http://en.wikipedia.org/w/index.php?title=Water&oldid=305251617

Figures Gully Erosion. (2007). Picasa Web Albums. Retrieved 30 July, 2009 from http://lh4.ggpht.com/_8WHwy0YGBc/RrcYj6aN7mI/AAAAAAAAAF8/kom7uqAQybM/P1110630.JPG Hydrothermal Power Systems. (2008). Geothermal Technologies Program. U.S. Department of Energy. Retrieved 27 July, 2009 from http://alternateformsofenergy.com/Geothermal/images/How-a-Geothermal-Power-PlantWorks_clip_image003.gif Major Categories of Erosion. (2003). Van Buren County Community Center. Retrieved 30 July, 2009 from http://www.vbco.org/media/planningeduc/tn_raindrp.jpg Old Faithful Geyser. (2003). Photo gallery. Aroundhere.ca. Retrieved 27 July, 2009 from http://www.aroundhere.ca/Gallery/Old-Faithful-Geyser-Yellowstone.jpg Sheet Erosion. (2006). Webshots. Retrieved 30 July, 2009 from http://image61.webshots.com/161/5/98/41/540559841ZonHRJ_fs.jpg Water Water Everywhere. (2008). Conveyerblog.com. Retrieved 27 July, 2009 from http://weblogs.newsday.com/news/local/longisland/politics/blog/water.jpg

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