1. 5.2 – NOTES Water A

2. 2 water related challenges faced every day-
Can we get enough water?
Is the water pure enough?

3. B.1 Physical Properties of Water
The Earth is unique because it has so much water.
70+% of Earth's surface is covered with oceans of an average depth of 3 km
Matter
Anything that has mass and takes up space

4. Physical property
Properties of the senses – can be observed without changing the make- up of the substance
Density
The measure of mass in a given volume
The formula for density is D = M V
The density of water at 25 0C is g/ml

5. Freezing point of water is
An unusual property of water is that solid water is less dense than liquid water
Aqueous solutions- solutions that are dissolved in water
NH3 (aq)  shows its aqueous solution
Pure water is clear, colorless, odorless, and tasteless, which are physical properties

6. B2. Density
Practice Problem: In the foul water lab, you observed that coffee grounds settled to the bottom of the water sample, whereas oil floated on top. Explain this observation in terms of the relative densities of coffee grounds, water and oil.
Highest Density  Coffee Grounds  Water  Oil  Less Dense

8. Purity is a relative term
100% pure water is impossible in a municipal system
Cost – very expensive to remove everything
Dissolved Gases – gases dissolve very easily and are hard to get out
What are some other impurities that may be found in water?
Disinfecting agents, mud, trash, skin, algae, fish, sticks

9. ChemQuandry, page 8
It takes approximately 120 L of water to produce one 1.3 L can of fruit juice. It takes about 450 L of water to place one fried egg on your breakfast plate. Think of possible explanations for these two facts.
Direct vs Indirect uses of water
Direct – measureable
Indirect – Can’t Measure

10. A.3 Foul Water
Filtration
Process of separating solid particles from a liquid by using a membrane
Filtrate
Liquid left after filtration; residue = solid particles
Adsorption
Attraction of impurities to the surface of something ; charcoal absorbs odor and color
Percent recovery
% of purified water recovered at the end of the purifying process
% recovery = final volume
initial volume x 100

11. A.4 Water Supply and Demand
15 trillion L (4 trillion gallons) of precipitation falls in the US each day
10 % of this is used by humans
Water Cycle
Also called the hydrologic cycle
Continuous cycling of water through atmosphere

12. Diagram of the Water Cycle

13. Average family of 4 uses 1200 L of water/day
Direct use only
Use that can be directly measured
Indirect use - can’t be directly measured
We are generally unaware of how much water we actually use each day
Anecdote about my water situation

14. A.6 Where is the World's Water?
Water is unusual due to the fact that it exists as all 3 states (solid, liquid, gas) at normal conditions
Most of the US has abundant supplies of water
Surface water- water that is exposed to the atmosphere, rivers, lakes, streams, oceans, etc

15. Groundwater- must be pumped to the surface to be used; in wells
 1/5 of all water is groundwater
Aquifer- water holding layer of rock, sand, or gravel that is a holding are for groundwater

16. The majority of water must be purified before being used
Picks up dissolved gas, rocks, soil as it travels through the ground/pipes
Where is it?
97.2%- oceans
2.8%- freshwater
2.11%- glaciers/ice caps
0.62%- groundwater
0.009%- lakes
0.001%- atmospheric moisture
0.0001%- rivers