The Extraordinary Properties of Water

Water is a compound – substance made of 2 or more elements in definite proportions. 2 atoms of hydrogen (H) and 1 atom of oxygen (O). Most abundant compound in most living things. 2H + O -> H2O Can you identify reactants and product? How many atoms are in the above molecule? Water is polar

Water molecules are polar, with the oxygen side being slightly negative and the hydrogen side being slightly positive. Water dissolves many ionic and molecular compounds because of this polarity. The difference in the relative attraction of the electrons determines the polarity of a bond.

Hydrogen bonds are the reason water is a liquid at room temperature – adjacent H2O molecules form hydrogen bonds. Ionic and covalent bonds are intramolecular bonds, meaning that they exist inside the molecule. These bonds deal with the exchange of electrons. Hydrogen bonds are intermolecular bonds, meaning they bond two separate molecules. Hydrogen Bonds

What are the Properties of Water? 1

1. Cohesion Attraction between particles of the same substance ( why water is attracted to itself) Results in surface tension (a measure of the strength of water’s surface) 1

Helps insects walk across water Cohesion … Helps insects walk across water

2. Adhesion Attraction between two different substances. Capillary action-water molecules will “tow” each other along when in a thin glass tube. 1

Adhesion and capillary action…

3. High Heat of Vaporization 4. High Specific Heat As water evaporates, it removes heat with it (cooling effect) Water resists temperature change, both for heating and cooling. Water vapor forms a global ‘‘blanket” which helps to keep the Earth warm. 1

5. Water is Less Dense as a Solid Ice floats on water because water expands when it freezes. Therefore, ice is less dense as a solid. 1

Water is Less Dense as a Solid Which is ice and which is water? 1

Water is Less Dense as a Solid Ice 1

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