Do Now: What do you know about H 2 O

Basic Information of H 2 O  Covers 71% of the Earth’s surface  Of that 71%, 97% is salt water, and 3% is fresh water  Of that 3% of freshwater, only 1% is used for human consumption  Most of the freshwater are found in ice caps and glaciers

Types of Water  Surface water- fresh water on Earth’s Land Surface  Lakes, rivers, streams, and wetlands  Most large cities today depend on surface land for their water supply  Rivers, Lakes and Streams provide water for drinking, growing crops, means of transportation, and power for industry

 Groundwater- freshwater beneath the Earth’s surface  Most of the freshwater that is available for humans comes from the ground water.

Global Water Use  Globally, only 8% is used for household use  About 67% for agriculture uses  About 19% for industrial uses  On average, the United States uses about 300L (80gal) of water a day  In India, an average person uses 41L a day

Daily Water Use in United States (per person) UsesWater (L) Lawn watering and pools95 Toilet Flushing90 Bathing70 Brushing Teeth (while water is running) 10 Cleaning (inside and outside)20 Cooking and drinking10 Other5

Water Treatment  Potable- process which water is treated to be safe to drink  Removed elements such as mercury, lead, arsenic, and pathogen which are all poisonous to humans even in low concentrations

Industrial Uses  Used to manufacture goods, dispose wastes, and to generate power  Most of the water used in industry is to cool power plants  Nearly 1000L of water is used to produce 1 kg of aluminum, and almost 500,000L of water is used to manufacture a car

Agricultural Uses  It takes 300L of water to produce 1 ear of corn  Plants require a lot of water to grow, and as much as 80% evaporates and never reaches the plants  Irrigation- water transporting from other means than direct precipitation

Water Conservation  Most inexpensive way to ensure will have enough water  In agriculture, most water is loss through seepage, runoff, evaporation  Drip irrigation system is best used to get to the roots of the plants through perforated tubing at a controlled rate

 In the industry, they have developed a water conservation plan to recycle the cooling water and waste water  At home, taking shorter showers, not running the water when brushing teeth, putting the sprinklers on in the evening are all ways to conserve water

Chemistry Behind Water  High boiling point (100 degrees Celsius)  High surface tension- inward force that tends to minimize the surface area of liquid  Low Vapor Pressure

Why?  Hydrogen bonds

Chemistry of Ice  Typically, when a liquid cools to become a solid, the solid will be more dense than its liquid  With water, around 4 degrees Celsius, the density of water decreases from 1.00 g/mL (its original density) and it will no longer behaves like a liquid

 Structure of ice is a regular open framework of water molecules in a hexagonal arrangement

Snowflakes  Formed when supercooled droplets freeze around the droplet’s nucleus  Supercooled droplets are drops that are still water below freezing (about -18 degrees Celsius)  Once the droplet is frozen, it grows in a supersaturated environment where the deposition of water from the vapor collects onto the ice crystal