Water Chemistry H2O

Valence Electrons: the electron(s) in the outer shell of an atom’s electron cloud, which can combine with other atoms to form molecules *The number of valence electrons in an atom of an element determines many properties of that element, including the ways in which the atom can bond with other atoms.

Chemical bonds hold molecules together Chemical bonds hold molecules together . A chemical bond is a union between atoms formed when they give up, gain, or share electrons .

3 types of bonds Ionic Covalent –Non-polar –Polar Hydrogen

Ions Ions: When an atom loses an electron, it loses a negative charge and becomes a positive ion. When an atom gains an electron, it gains a negative charge and becomes a negative ion.

Ionic Bonds Description •Ionic Bond: give up or gain electrons The resulting oppositely charged ions attract one another, forming an ionic bond.

Ionic Bonds You and a friend walk past a market that sells apples for 40 cents each and pears for 50 cents each. You have 45 cents and want an apple. Your friend also has 45 cents but wants a pear.

Ionic Bonds Example For example, in table salt (sodium chloride) the negative chlorine ion attracts the positive sodium ion, forming an ionic bond.

Covalent Bonds Descriptions A covalent bond shares one or more pair of electrons Non-polar covalent bond: atoms share electrons equally Polar covalent bond: atoms share electrons unequally

Covalent Bonds Examples . Covalent Bonds Examples For example, carbon dioxide molecule is a nonpolar molecule because of its straight-line shape.

Covalent Bonds An example of a polar molecule is water because of its bent shape.

Hydrogen Bonds Description Hydrogen Bonds: form when partial opposite charges in different polar molecules attract each other. These are weak bonds.

Hydrogen Bonds Example The only example of hydrogen bonding is when two or more water molecules are attracted. One water molecule can attract up to 4 other molecules.

Structure and Properties of Water Water Flashcards Structure and Properties of Water   Draw a picture Take notes (black) Interesting facts (in blue) --- not required to know

Structure of Water Polar Covalent Bonds H2O    H2O Electrons are shared unequally Oxygen is negative (O: -) Hydrogen is positive (H: +) Stronger pull towards Oxygen (larger atom) Hydrogens repel each other.

Structure of Water Hydrogen Bonds Water to Water   Water to Water Hydrogen (+) is attracted to Oxygen (-) 1 H2O can attract 4 H2O’s

Properties of Water 3 Phases Solid, Liquid, Gas   Solid, Liquid, Gas Unique - only substance that can exist in all 3 states of matter naturally on Earth. Can exist in all 3 states of matter and the exact same time in the same place.

Stabilize Temperature Properties of Water Stabilize Temperature   High Specific Heat Water resists temperature changes Can absorb or release large amounts of heat energy Heat of Vaporization In order for water to evaporate hydrogen bonds must be broken. When water evaporates it removes a lot of heat with it. This is why sweating works to cool down.

Properties of Water Universal Solvent Dissolves   Dissolves Water is a polar molecule which attracts + and – ions. Water dissolves salt (Na+ Cl-) Dissolves more than anything else (including acids)

Properties of Water Density Freezing water Water’s density is 1 g/cm3.   Freezing water Water’s density is 1 g/cm3. Water’s density decreases () as temperature decreases () Freezes = molecules spread slightly apart creating spaces between them. Ice floats in liquid water. This is also why fish and plants in a pond or lake do not die every winter. Bodies of water freeze from the top down and never all the way through.

Properties of Water Transparency Visible Light   Visible Light Light can penetrate making photosynthesis possible It is transparent because it doesn’t absorb light in the visible spectrum Why is the ocean blue? And a cup of water clear? Cup – not enough molecules to absorb light Ocean – water molecules strongly absorb long- wavelength colors at the red-end of the spectrum, blue light is then reflected.

Properties of Water Cohesion Surface Tension Sticks to itself   Surface Tension Sticks to itself Water is polar = “sticky” The molecules at the surface do not have other like molecules on all sides so they stick together more strongly creating a “film.” These surface molecules are only pulled in a downward direction.

Properties of Water Adhesion Capillary Action   Capillary Action Water sticks to other surfaces. Like a straw, capillary action is the rise of a liquid that wets the diameter of a small tube. This climbing effect is created because the water adheres to another surface, but also the cohesive force of water “tows” other water molecules up the surface. This is why tall trees do not die at the top. They bring water up from the ground.