1. 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 3 WATER AND THE FITNESS OF THE ENVIRONMENT

2. 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

3. Properties of water 1. _________- 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? ______________ Freezes at __ C and boils at ____ C As a liquid evaporates, the surface of the liquid that remains behind cools - ______________________.

4. 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

5. # of molecules in a mole = _______________ =6.02 x 10 23. 1 mole ethyl alcohol (C 2 H 6 O) = 46g (also contains ___________________ How do measure amounts? Answer- In ______ A _________ = molecular weight (in grams) Example - sucrose (C 12 H 22 O 11 ) 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

6. How do we measure acidity? Answer: ___________. A water molecule dissociates into a hydrogen ion and a hydroxide ion: H 2 O H + + OH - At equilibrium the concentration of H + or OH - is 10 -7 M (25°C). Hydrogen and hydroxide ions are very reactive, and thus drastically affect the proteins and other molecules of a cell.

7. 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

8. 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