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Water

• Pure water boils at 100⁰C.
• Pure water freezes at 0⁰C.
• Pure water has a pH number of 7.
• Pure water does not conduct electricity.
• The processes involved in the water cycle.
• Filtration is used to clean water.
• How clouds are formed.
• A liquid evaporates to make gas.
• A gas condenses to form a liquid.
• Wind direction can influence the type of weather.

More than 70% of the Earth's surface is  covered by water. When the Apollo space missions beamed back pictures of the Earth, public attention was caught by the image of a "Blue Planet," because of the vast expanses of ocean covering the globe. Yet despite this seemingly inexhaustible supply (approximately 370 billion billion gallons) of water on earth, access to clean drinking water remains a major challenge for a large percentage of the world's population. Almost 97%of the Earth's water is in the oceans. Less than 1% of the water on the earth is fresh water (the remaining 2-3% is contained in glaciers and ice caps).

Water is indispensable for life, not only for drinking water, but also for raising crops for food. Fishing provides a major source of protein for much of the world's population. Throughout history, cities and villages have grown up near sources of water, for drinking, sustenance, and transportation.

In this century, population growth has increased in areas where fresh water is relatively scarce. Water in these areas is a valuable commodity and, in some cases, great technological feats have been undertaken to provide a reliable source of water. Where does your drinking water come from? Well, the bottled water comes usually from underground wells at Masafi, Al Ain and Hatta! The water that comes out of our taps comes from the sea! It is desalinated - the salt is removed from it! Because we live in the desert, water is a very valuable resource.

The hydrologic Cycle (also called the Water Cycle) is the process that moves water around the earth. The term "hydrologic cycle" refers to the constant movement of water above, on, and below the earth's surface. The Water Cycle can change the form of water from liquid to water vapor to ice, and even clean it along the way, but it can’t make more water. Water is not created or destroyed, but simply changes location and form. The water you drink today may have been lapped up by dinosaurs millions of years ago, or helped fill Julius Caesar’s bathing pool. The water we use now is the same supply the human race started with. Its quality is renewed again and again by the natural hydrologic cycle.

The sun is the energy that powers this remarkable process. Its energy in the form of light and heat causes water to EVAPORATE from oceans, rivers, lakes and even puddles. Evaporate means it turns the water from a liquid to a gas, or vapor. Warm air currents rising from the earth’s surface lift this water vapor up into the atmosphere.

When the air currents reach the cooler layers of the atmosphere, the water vapor condenses around and clings on to fine particles in the air. This step is called CONDENSATION. When enough vapor attaches itself to tiny pieces of dust, pollen or pollutants, it forms a cloud. Clouds do not last forever. Old clouds constantly re-evaporate and new ones form, creating ever-changing patterns in the sky.

As the air gets more and more moist, the droplets that form the clouds grow larger and larger. Eventually they will get so big that the swirling atmospheric winds can no longer hold them up. The droplets then fall from the sky as PRECIPITATION. Precipitation can be in the form of rain, snow, sleet or hail depending on other atmospheric conditions such as temperature.

Once the precipitation reaches the ground, several things can happen to it. First, it might re-evaporate. For instance, we’ve all seen the mist rising off hot roads after a summer shower. If it isn’t re-evaporated, much of the water will become SURFACE RUN-OFF that goes into streams, rivers, or ponds as it flows back to the ocean.

Some of the precipitation will be absorbed into the ground. This is called INFILTRATION. Once in the ground, the water can join the earth’s GROUNDWATER supply. This is one of the world’s largest storehouses of water. As water sinks into the soil it flows through underground reservoirs or aquifers. The water could also be absorbed from the ground by the roots of plants. Water passes through many different aquatic habitats before gravity pulls it to earth’s lowest point, the ocean.

Another form of evaporation that contributes to the water cycle is TRANSPIRATION. Here, water given off through the pores of plants and animals joins the atmosphere as a vapor. Check, for instance, your own breath on a cold day. What you are seeing is water vapor being given off by your body.

With transpiration and evaporation, the cycle begins again: EVAPORATION, CONDENSATION, PRECIPITATION, SURFACE RUN-OFF, INFILTRATION, and TRANSPIRATION. Each time a molecule of water goes through the cycle it is cleaned, or purified, so it can be used by plants and animals again tomorrow, next year, and hopefully forever.

WATER CONSERVATION FACTS:

• The human body is about 75% water.
• Showering and bathing is one of the largest users (27%) of water domestically.
• Less than 2% of the Earth’s water supply is fresh water.
• The average American uses 140-170 gallons of water per day.
• A leaky tap can waste up to 100 gallons a day.
• One flush of the toilet uses 6 ½ gallons of water.
• An average bath requires 37 gallons of water.
• An average family of four uses 881 gallons of water per week just by flushing the toilet.
• The average shower takes about 20 gallons of water, around 40 gallons are used in 10 minutes.
• You use about 5 gallons of water if you leave the water running while brushing your teeth.
• If you water your grass and trees more heavily, but less often, this saves water and builds stronger roots.
• Each person needs to drink about 4 pints of water everyday.
• Water your lawn only when it needs it. If you step on the grass and it springs back up when you move, it doesn’t need water. If it stays flat, it does need water.

WATER CONSERVATION TIPS:

• Run your dishwasher and washing machines only when they are full.
• When washing a car, use soap and water from a bucket. Use a hose with a shut-off nozzle for rinsing.
• Never put water down the drain when there may be another use for it such as watering a plant or garden, or cleaning.
• Avoid flushing the toilet unnecessarily. Dispose of tissues, insects and other such waste in the trash rather than the toilet.
• Put a brick or piece of block paving in the toilet cistern to reduce the amount of water used to flush.
• When washing dishes by hand, fill one sink or basin with soapy water. Quickly rinse under a slow-moving stream from the tap.
• Store drinking water in the fridge rather than letting the tap run every time you want a cool glass of water.
• Water lawns during the early morning hours, or evening when temperatures and wind speed are the lowest. This reduces losses from evaporation.
• Do not hose down your driveway or pavement. Use a broom to clean leaves and other debris from these areas. Using a hose to clean a driveway can waste hundreds of gallons of water.
• Encourage your school to help develop and promote a water conservation ethic among children and adults.
• Take short showers instead of baths. A full bathtub requires about 36 gallons of water.
• Don’t leave the water running when brushing your teeth or shaving. Get in the habit of turning off the water when it’s not being used.
• Use of bowl of water to clean fruits & vegetables rather than running water over them. You can reuse this for your house plants.
• Conserve water because it is the right thing to do. Don’t waste water just because someone else is footing the bill such as when you are staying at a hotel.
• Try to do one thing each day that will result in a savings of water. Don’t worry if the saving is minimal. Every drop counts. And every peron can make a difference. So tell your friends and family to “Turn it Off” and Keep it Off”.

What you should be able to do.

• List 5 uses of water.
• label a diagram of the water cycle.
• Carry out filtration.
• Explain why it rains.