1. The polarity of water molecules results from hydrogen bonding

• Water molecule- two hydrogen atoms form ____________________ bonds with an oxygen atom.

• Partial negative charge

• Partial positive charge

_____- because each share one electron______- because O is more electronegative than H________- because they each share electrons

CHAPTER 3WATER AND THE FITNESS OF THE

ENVIRONMENT

• Water has unusual properties because of attractions between ______ molecules.

• The slightly negative regions interact with slightly positive regions of nearby molecules, forming a _________________.

• Each water molecule can form hydrogen bonds with up to ________ neighbors.

Fig. 3.2

Properties of water1. _________- Hydrogen bonds hold

water together.

2. High ______________

Water “pulled up” to tree tops

“an invisible film”

3. _____________ air temperatures

• Water resists changes in temperature Why? _____________

Why? _____________

Why? ______________

• Freezes at __ C and boils at ____ C• As a liquid evaporates, the surface of the liquid that remains behind cools - ______________________.

4. Ice is about ________ dense than water at 4oC, thus ice ______

Thus, oceans and lakes don’t freeze solid

5. Water is the solvent of life

Why? It forms _____________________ with many molecules

• # of molecules in a mole = _______________ =6.02 x 1023.

• 1 mole ethyl alcohol (C2H6O) = 46g (also contains ___________________

How do measure amounts? Answer- In ______• A _________ = molecular weight (in grams)

• Example - sucrose (C12H22O11)

• A carbon atom weighs 12 daltons, hydrogen 1 dalton, and oxygen 16 daltons.

• The _________________ of sucrose is 342 D.

• (12 x 12D) + (22 x 1D) + (11 x 16D)

• Thus, one mole of sucrose weighs 342 g

• How do we measure acidity?

• Answer: ___________.

• A water molecule dissociates into a hydrogen ion and a hydroxide ion:

• H2O <=> H+ + OH-

• At equilibrium the concentration of H+ or OH- is 10-7M (25°C) .

• Hydrogen and hydroxide ions are very reactive, and thus drastically affect the proteins and other molecules of a cell.

• The _________ of their __ and ____ concentrations is constant at _______.

• [H+] [OH-] = 10-14

• In a neutral solution, [H+] = ___M and [OH-] = ____ M

• If add acid, H+ ions increase and OH- ions decrease.

• The H+ and OH- concentrations of solutions can vary by a factor of 100 trillion or more.

• The H+ and OH- concentrations are typically expressed via the ___________.

• The pH scale, ranging from ________, compresses the range of concentrations by employing ___________.

• pH = - log [H+] or [H+] = 10-pH

• In a neutral solution [H+] = ___M, and the pH = __.

• Values for pH decline as [H+] _______.

• Most biological fluids have pH values in the range of ______.

• Each pH unit represents a ________ difference in H+ and OH- concentrations.

Fig. 3.8