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Water and the Water Molecule. A short lesson on water molecules designed for the Junior High science curriculum. This lesson will…. Define the term molecule . Outline the formation of a water molecule. Introduce the characteristics that make water so unusual.
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Water and the Water Molecule A short lesson on water molecules designed for the Junior High science curriculum.
This lesson will… • Define the term molecule. • Outline the formation of a water molecule. • Introduce the characteristics that make water so unusual. Image retrieved from: http://www.accs.net/users/kriel/chapter%20seven/water%20polar.gif
Electron (-) Nucleus (+) Hydrogen Atom Before we start, let’s quickly review the definition of an atom. An atom is the smallest possible particle of a chemical element.
O O O H H H H H H The Molecule • A molecule is a group of two or more atoms held together by chemical bonds. • Water is a molecule. • Ever hear someone call water, H2O?
Chemical Bonds Definition: The energy relationship between two or more atoms that hold them together. • Chemical bonds are formed when electrons are shared between atoms or moved from one atom to another.
O O H H H H We call it H2O because water molecules are formed when electrons are shared between two Hydrogen atoms and one Oxygen atom.
+ 2- 105° O + H H The Water Molecule • The angle formed by the 2 Hydrogen atoms and the 1 Oxygen atom is about 105°. • Water molecules have a positive (+) and negative (-) end. • This makes it attract to other water molecules.
Hydrogen Bonds • Hydrogen bonds form when the positive (+) end (the H atom) of one water molecule is attracted to the negative (-) end (the O atom) of another water molecule. Hydrogen Bond
Cohesion & Adhesion • Hydrogen bonds influence the properties of water by allowing individual water molecules to stick to each other. This is called cohesion. Cohesion gives water it’s surface tension. • Ever see an insect walk on water? • Adhesion allows water to stick to solid materials and make them wet.
Water • The most abundant molecule of earth. • About 70-75% of the earth’s surface is liquid and solid water. • Water molecules are also found in our atmosphere in the form of vapor. • The only pure substance found naturally in all three states of matter – liquid, solid, gas.
About the Author Mark Riley is a second year graduate student in the Curriculum & Instruction program at Ohio University. Please contact him by email at mr389997@ohio.edu Click the button to restart this PowerPoint.
References Garrison, T. (2006). Essentials of Oceanography (4th ed.)(p. 108). Belmont, CA: Thomson Brooks/Cole. http://en.wikipedia.org/wiki/Water_(molecule) http://en.wikipedia.org/wiki/Molecule