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Biology Homework

Teacher´s Name: Gerardo Lázaro Student´s Name : Carlos Noriega García Topic: Find out the day the UN selected to celebrate the world importance of Water, and investigate the main chemical properties of the molecule of water. Grade: 7th Beethoven Date: March 23rd, 2009

Elaborated by: Carlos Noriega García


Biology Homework

International World Water Day International World Water Day is held annually on 22 March as a means of focusing attention on the importance of freshwater and advocating for the sustainable management of freshwater resources. An international day to celebrate freshwater was recommended at the 1992 United Nations Conference on Environment and Development (UNCED). The United Nations General Assembly responded by designating 22 March 1993 as the first World Water Day. Each year, World Water Day highlights a specific aspect of freshwater. On this page, we present a brief overview of the different themes that have been the focus of World Water Day celebrations. Sources of information: http://www.unwater.org/worldwaterday/about.html

Water's Chemical Properties You probably know water's chemical description is H2O. As the diagram to the left shows, that is one atom of oxygen bound to two atoms of hydrogen. The hydrogen atoms are "attached" to one side of the oxygen atom, resulting in a water molecule having a positive charge on the side where the hydrogen atoms are and a negative charge on the other side, where the oxygen atom is. Since opposite electrical charges attract, water molecules tend to attract each other, making water kind of "sticky." As the right-side diagram shows, the side with the hydrogen atoms (positive charge) attracts the oxygen side (negative charge) of a different water molecule. (If the water molecule here looks familiar, remember that everyone's favorite mouse is mostly water, too).

All these water molecules attracting each other mean they tend to clump together. This is why water drops are, in fact, drops! If it wasn't for some of Earth's forces, such as gravity, a drop of water would be ball shaped a perfect sphere. Even if it doesn't form a perfect sphere on Earth, we should be happy water is sticky. Water is called the "universal solvent" because it dissolves more substances than any other liquid. This means that wherever water goes, either through the ground or through our bodies, it takes along valuable chemicals, minerals, and nutrients.

Sources of information: http://ga.water.usgs.gov/edu/waterproperties.html

Elaborated by: Carlos Noriega GarcĂ­a


7th Beethoven - Importance of Water - Carlos Noriega