The Extraordinary Properties of Water

1. Ionic Bonds Types of Bonds: An ionic bond forms between a metal (cation) and a non metal (anion). Electrons are completely transferred between atoms in an ionic bond. When an atom gains or loses electrons it becomes a charged atom called an ION.

2. Covalent Bond Covalent bonding is between more than one nonmetal. Two atoms SHARE electrons. Covalent bond = molecular compound A molecule is the basic unit of a molecular compound. These bonds can either be polar or nonpolar.

 Occurs when two atoms equally share a pair of electrons.  The diatomic elements are examples of molecules containing a nonpolar covalent bond. Nonpolar Covalent Bonds OO *Like DISSOLVES like* Nonpolar molecules can only mix with other nonpolar molecules

Occurs when two atoms do not equally share a pair of electrons. As a result of the unequal sharing of an electron pair, the molecule has one end which is partially negative ( δ-) and one end which is partially positive ( δ+). The negative end of one polar molecule will be attracted to the positive end of another polar molecule. Polar Covalent Bonds *Like DISSOLVES like* Polar molecules can only mix with other polar molecules. Ionic Bonds can also mix with polar bonds.

Water is Polar Because the oxygen end “acts” negative and the hydrogen end “acts” positive water is said to be POLAR

slightly positive charge slightly negative charge hydrogen bond between (+) and (-) areas of different water molecules A water molecule attaches to another water molecule by an intermolecular force called Hydrogen bonding. A positive region of the molecule is attracted to the negative region of another molecule.

Water can change Phases of Matter by: melting freezing evaporation sublimation condensation deposition

Water is Less Dense as a Solid Ice is less dense as a solid than as a liquid (ice floats) Liquid water has hydrogen bonds that are constantly being broken and reformed. Frozen water forms a crystal-like lattice whereby molecules are set at fixed distances.

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

Properties of Water: Homeostasis Homeostasis is the ability to maintain a steady state despite changing conditions Water is important to this process because: a. Makes a good insulator b. Resists temperature change c. Universal solvent (can dissolves almost everything in the world) d. Coolant e. water freezes from the top down; insulating lakes so that organisms can still live in the water underneath the ice during winter

Properties of Water: Temperature At sea level, pure water boils at 100 °C and freezes at 0 °C. The boiling temperature of water decreases at higher elevations (lower atmospheric pressure). For this reason, an egg will take longer to boil at higher altitudes

Properties of Water: Cohesion Cohesion is the attraction between two like molecules ( why water is attracted to itself) Cohesion results in Surface tension (a measure of the strength of water’s surface)

Cohesion … Cohesion produces the surface tension of water that allows insects to walk on the surface of water

Properties of Water: Adhesion Adhesion is the attraction between two unlike molecules. Water will make hydrogen bonds with other surfaces such as glass, soil, plant tissues, and cotton. Capillary action- because of adhesion a liquid can rise up a small tube.

Capillary action water evaporates from leaves = transpiration adhesion, cohesion and capillary action All thanks to hydrogen bonding! water taken up by roots

Adhesion Also Causes Water to … Form spheres & hold onto plant leaves Attach to a silken spider web

Properties of Water: High Specific Heat High specific heat is the amount of heat needed to raise or lower 1g of a substance 1° C. Water resists temperature change, both for heating and cooling. Water can absorb or release large amounts of heat energy with little change in actual temperature.

Properties of Water: High Heat of Vaporization High heat of Vaporization is the amount of energy to convert 1g or a substance from a liquid to a gas In order for water to evaporate, hydrogen bonds must be broken. As water evaporates, it removes a lot of heat with it.

Water vapor forms a kind of global ‘‘blanket” which helps to keep the Earth warm. Heat radiated from the sun warmed surface of the earth is absorbed and held by the vapor. *Without water our planet would not sustain life as you know it.*