1/18 Assignment: DHMO Read the article on DHMO. Discuss in your groups the answers to the following questions. In your notebook, write the answer to these questions. You must write in complete sentences but don’t have to write the question. 1) Should DHMO be banned. Give a reason why or why not? 2) What are two hazards of DHMO and two benefits of DHMO to humans? 3) What chemical do you think DHMO is?

1/18 Homework Fill out the information on the back page of your syllabus and have your parent or gaurdian sign it. Return the assignment to Mr. O by next Wednesday. (10 pts)

Chemistry In The Environment: Water

Distribution of WATER 70.9% of the Earth’s surface is covered by water. Oceans hold 97% of surface water. Glaciers and polar ice caps hold 2.4% Rivers, lakes, ponds and groundwater holds contains the remaining 0.6% A very small amount of the Earth’s water is contained within biological bodies and manufactured products.

We need freshwater!!!! Only 2.5% of water on the Earth is fresh water, and over two thirds of this is frozen in glaciers and polar ice caps. Water demand already exceeds supply in many parts of the world, and many more areas are expected to experience this imbalance in the near future

Chemical and Physical Properties Water is liquid at STP. It is tasteless and odorless. All 3 common states, solid, liquid and gas appear in nature.

Physical and Chemical Properties Clean drinking water is essential to humans and other life forms. Humans and other animals have developed senses which enable them to evaluate the potability of water by avoiding water that is too salty or putrid.

Water is transparent in the visible electromagnetic spectrum Aquatic plants can live in water because sunlight can reach them. Ultra violet and infrared light is strongly absorbed.

Water is a polar molecule (unequal sharing of electrons) with a bent shape. This causes strong attractive forces between molecules of water. Allowing it to have high surface tension and capillary forces.

Water is a Universal Solvent HYDROPHILIC (water loving) Substances that dissolve in water like salts, sugars, acids, alkalis and some gases like oxygen and carbon dioxide. HYDROPHOBIC (water fearing) Substances that do not mix well with water such as fats and oils.

All the major components in cells are dissolved in water

Other fun facts about water!!! Pure water has a low conductivity. The boiling point of water is dependent of the barometric pressure. Water on the top of Mt. Everest boils at 68 o C compared to 100 o C at sea level.

Why does ice float? The maximum density of water occurs at 3.98 o C. As water freezes it expands to occupy 9% greater space in its solid form that in its liquid state.

How does water help moderate temperature? Earth is a complex and dynamic system with a surface that is more ocean than land. The ocean interacts continually with the atmosphere, by exchanging, storing, and transporting matter and energy. Water bodies have a much higher heat capacity than land and intercept more incoming sunlight than land surfaces because of its greater transparency.

The Water Cycle (Hydrologic Cycle) The water cycle refers to the continuous exchange of water within the hydrosphere between the atmosphere, soil, water, surface water, groundwater and plants.

Evaporation Solar energy strikes the ocean water causing water molecules to escape from the liquid and rise as gas

Transpiration Plants lose moisture through small holes in their leaves

Condensation Water vapor condenses as clouds

Precipitation Moisture released by clouds (clouds are droplets of water). Rain, snow, sleet and hail

DISTRIBUTION Of WATER 70.9% of the Earth’s surface is covered by water. Oceans hold 97% of surface water. Glaciers and polar ice caps hold 2.4% Rivers, lakes, ponds and groundwater holds contains the remaining 0.6% A very small amount of the Earth’s water is contained within biological bodies and manufactured products.

Water Purification Water purification is the process of removing undesirable chemicals, materials, and biological contaminants from contaminated water.

Why do we purify water? Human consumption – drinking water Medical applications Pharmacological applications Chemical applications Industrial applications

Methods of Water Purification physical processes such as filtration and sedimentation biological processes such as slow sand filters or activated sludge chemical processes such as flocculation and chlorination the use of electromagnetic radiation such as ultraviolet light.

Purification of Drinking Water The United States has nearly 60,000 municipal water facilities that serve 232 million people. Surface water sources of municipal water supplies include streams, rivers and lakes. Often a dam is built across a river or stream to form an artificial lake or reservoir. Reservoirs accumulate water when there is an adequate supply and store it for use during periods of drought.

Water Purification In the United States most municipal water supplies are treated before being used so that the water is safe to drink. Turbid water is treated with a chemical coagulant that causes the suspended particles to clump together and settle out (flocculation and sedimentation). The water is then filtered through sand to remove remaining suspended materials as well as many microorganisms.

Water Purification In the final purification the water is disinfected to kill any remaining disease causing agents. The most common way to disinfect water is to add chlorine. Other types of disinfection systems use ozone or ultraviolet(UV) radiation.

Water Purification Techniques Physical (Filtering, settling) Biological (Bacteria eat or organic matter in water) Chemical (Removal of chemicals and kill of pathogens) Distillation (boiling) Reverse osmosis (Filters so small they can block individual molecules larger than water)

What is distillation? Water is boiled and turned into a gas (water vapor.) The water vapor travels down a long tube where it is cooled. The water vapor then condenses back into liquid and is stored in a container Distallation removes nearly all impurities from the water because nothing else boils at the same temperature. Distallation is expensive because it takes a lot of energy to boil water. This is too expensive for large Municipal water treatment facilities.

Waste Spills Human waste Hazardous waste Landfill waste Radioactive waste