1. The Water Cycle The Earth has a limited amount of water
The water on Earth moves from the Earth to the sky and back to the Earth in a cycle.
This is called the water cycle

2. Steps of the Water Cycle
1. Evaporation
2. Condensation
3. Precipitation
4. Collection

3. The Cause of Phase Changes in Water Cycle
Kinetic Theory: All atoms and molecules move
When energy (thermal) is added, atoms move faster
Atoms and Molecules are naturally attracted to one another
They want to form bonds
However, when enough energy is added to these atoms, the bonds they form aren’t strong enough to hold them together
When this happens, the atoms undergo a phase change

4. Phase Changes Solid= little energy added, molecules stay together
Liquid= more energy added, molecules bond and break bonds
Gas=too much energy, molecules can’t keep bonds

5. 1) Evaporation Evaporation: process of turning liquid into gas.
Water (H2O) : thermal energy added to liquid water in lakes, rivers, oceans by radiation from sun and turns into a gas (water vapor)
In water cycle, the step where H2O enters the atmosphere

6. Remember!!! When a gas is heated, the molecules will speed up
As they speed up, they occupy more space and thus become lighter and unable to form bonds
Lighter (hotter) gases tend to rise
“Hot Air Rises” Principle

7. 2) Condensation Condensation: process of turning gas into liquid
Thermal energy is removed and water molecules begin forming bonds
Causes formation of clouds

8. Remember!!! When a gas is cooled, the molecules will slow down
As they slow down, they occupy less space and thus become heavier and able to form bonds
Heavier (colder) gas tend to sink
“Hot Air Rises” Principle

9. How to Clouds Form?
The amount of water vapor in the atmosphere is called relative humidity.
As temperature and pressure go down, molecules lose heat energy, they slow down and go from gas (vapor) to liquid
When this occurs, the water vapor has reached its Dew Point: temperature at which the water vapor begins to form liquid water
In the atmosphere, the little droplets of water form clouds by sticking to particles in the air called condensation nuclei (ex. dust, smoke, salt)
What happens if you increase temperature and pressure?

10. 3) Precipitation
Precipitation: tiny water droplets combine to form bigger droplets that the atmosphere can’t hold, so the water falls
Examples: rain, snow, sleet, and hail

11. 4) Collection/Runoff
When water falls back to earth as precipitation, it may fall back in the oceans, lakes or rivers or it may end up on the land surface

12. Quiz Time!
During which water cycle step does H2O enter the atmosphere?
a) Evaporation
b) Condensation
c) Precipitation
d) Transportation
How does H2O return to Earth’s surface from the atmosphere?

13. Quiz Time! Which step of the water cycle is represented by letter B?
a) Evaporation
b) Condensation
c) Precipitation
d) Transportation

14. Erosion Erosion: Loss of topsoil Agents:
Water (rivers, floods, glaciers)
Wind
Gravity
Effects of Erosion:
Loss of farmland (fertile soil)
Destruction of property (landslides)
Negative impact on wildlife (fish, plants)
Rate of erosion: how quickly erosion occurs

15. Factors Affecting Rate of Erosion
Soil erosion increases with:
Smaller soil particles that are loosely compacted
Sand vs. Soil
Areas with less vegetation
Roots hold onto soil preventing erosion
Clear cutting, tree thinning, or fires increase erosion
Areas with steep slopes (Gravity)

16. What area has the least erosion?
Areas that are flat with heavy vegetation experience little erosion

17. Types of Water
Surface Water
Ground Water
Local Water

18. Surface Water Water that sits or flows above the earth
Including lakes, oceans, rivers, and streams.

19. Ground Water
Water that flows or seeps downward and accumulates in the ground
Supplies springs and wells.
The point where water begins to collect is called the water table

20. Local Water
Rural (country) areas have a shortage due to falling water table
Phoenix & Tucson
Currently: water is abundant due to CAP
Future: Water shortages due to growth

21. Water Issues
How Much Water Is There?

22. 3 Factors that Affect Water Quantity
1) Population Growth
More people create greater demands for water
2) Precipitation Levels
3) Drought
“Water is the true wealth in a dry land" --Wallace Stegner
Water resources become less dependable
Water bodies become depleted
Reservoirs are low

23. 3 Factors that Affect Water Quality
1) Acid Rain
2) Agriculture
3) Factories and Chemical Pollutants

24. 1) Acid Rain
When fossil fuels are burned, sulfur and nitrogen gases are released into the air
These pollutants chemically combine with water forming sulfuric acid and nitric acids

26. Effects of Acid Rain
Damages Plants, Animals, and Buildings

27. 2) Agriculture Crops and Cows
Chemical fertilizers and animal manure runs off and is washed into ponds, rivers, & groundwater
Crops: Fertilizers
Rich in nutrients (Nitrogen, Phosphorus, Potassium) which increase algae growth when entering the water supply
When algae dies, bacteria decompose dead material and use up oxygen in water causing other organisms (fish, plant life) to die

28. 2) Agriculture Cows: Manure
Manure (poop) carries bacteria into the water supply which multiply and use up the oxygen in the water

29. 3) Factories and Chemical Pollutants
Factories: Metals from mining & gasoline refineries
Homes: Detergents, cleaning products
Highway Runoff: fuels, oil

30. Water Management: Dams and Reservoirs
Provide water storage for run-off
Dams & reservoirs along Salt and Verde Rivers supply irrigation & drinking water for metro Phoenix area
Disrupts river system

31. Tapping Groundwater Using ground water drops the water table
This leads to water shortages
This also leads to contaminations from pesticides and fertilizers

32. Ground Water Contamination

33. Treated Wastewater
Treated wastewater - sewage, industrial wastewater, or other effluent that is treated to a level necessary for its intended usage.
Used to –
Irrigate golf courses, lawns
Cool power plants
Irrigate crops