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Unformatted text preview: CH 305 Chapter 5 part 1: The Water We Drink In the US, Canada, Europe or Asia we usually have three choices of potable water: Tap water about 0.1c per quart Bottled water about $1 to $2 per quart Filtered tap water about 20c per quart So why would we drink bottled water? US Drinking Water Sources Ground Water: Aquifers (Water trapped 50-100ft underground inside sand or gravel). Accessed by drilling wells or using naturally occurring springs. Examples: Ogallala - one of largest, underlies eight states (SD-TX) Edwards - central TX Rainwater has to percolate down into the aquifer. The filtering that occurs usually results in very pure water. If contaminated, may take many years to flush itself clean. Takes a long time to refill. Surface water: lakes, rivers, reservoirs. Example: Lake Travis Refill rapidly after rain, or when snow melts. Usually the water has to be treated before it is potable. Other Wet Facts Water is originally believed to have come from volcanoes on the primitive Earth. Precipitation (rain/snow/ice/sleet etc.) varies greatly: Wettest: Mt Waialeale on Kauai, Hawaii: 460 average per yr. Driest: Arica, Chile: 0.03 average per yr. Where is Earths water? 97.4% in the oceans. This is non-potable. 2.59% in ice caps, glaciers, groundwater (much stays frozen) 0.014% in surface water and in the soil or atmosphere ONLY ~0.01% of the Earths TOTAL water is conveniently accessible as fresh water! .. and we use 80% of the USs fresh water for irrigation and coolant water! Water in our Bodies The human body is over 60% water! Blood plasma contains water and is essential for life: -part of the O 2- CO 2 cycle of respiration. Water moves nutrients throughout the body & flushes out excess toxins that the body produces. But: If the water is contaminated, toxins can also be brought into the body. Water in the Environment There is an extremely complex cycle of water on Earth. Water removes or reduces pollutants by a dilution and/or flushing action: e.g., rain removes some substances from the atmosphere and deposits them on the Earth. However, these substances are then spread throughout the environment. Water as a Solvent Your Turn 5.6, page 224 Water is an excellent SOLVENT. It dissolves a lot of substances, but not everything. To determine which substances dissolve in water (SOLUTES) to form an AQUEOUS SOLUTION we will need to look at the chemical properties of water in more detail, and also see how we quantify how much can dissolve. Concentration Units Percentage --> parts solute per hundred parts solution Your Turn 5.7, page 225; Your Turn 5.9, page 227 Example: Hydrogen Peroxide for 1st aid is usually 3%: 3g hydrogen peroxide per 100g solution....
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- Spring '08