How Important Is Water???

Water (H2O) 70% of your body is made of water 2/3 of the molecules in your body are water molecules

I. Properties of Water 1. high specific heat– water heats slowly and retains heat longer than most substances; this allows the temperature of water to remain relatively constant protecting life on Earth from hot lethal temperatures and from freezing

Why does water not overheat? Water can absorb a lot of heat with only a small increase in temperature Water can retain heat for longer periods of time so temperatures don’t drop as quickly Why does water not freeze?

 IF water tends to overheat in the body, cells maintain homeostasis by releasing excess heat through water evaporation = sweating.

2. cohesion – an attraction between substances of the same kind. This attraction between water molecules causes a condition known as surface tension. Surface tension prevents the surface of water from breaking easily

3. adhesion – an attraction between different substances; adhesion powers a process called capillary action; for example, water moving up the roots & stems of plants

polar molecules –have a positive charge on one end and negative charge on the other; polar molecules and ionic compounds dissolve best in water because they are attracted to the ends of water molecules with the opposite charge Water (H2O) is considered a polar molecule! Salt (Na+Cl-) dissolves in water because each atom has a charge.

nonpolar molecules – do not dissolve well in water because the water molecules are more attracted to each other than the nonpolar molecule; nonpolar molecules do not have an electrical charge; nonpolar substances dissolve in oil

Ionic Compounds/

acids – a solution that has an excess of H+ (hydrogen) ions III. Acids and Bases H2O H+ + OH- ( HOH ) hydrogen ion hydroxide ion acids – a solution that has an excess of H+ (hydrogen) ions base – a solution that has an excess of OH- (hydroxide) ions

PH Scale: pH – potential of hydrogen; it measures the hydrogen ion concentration in a liquid

EX: A pH of 4 is how much more /Basic /Basic Each whole number on the pH scale represents a factor of 10. EX: A pH of 4 is how much more acidic than a pH of 6? A pH of 2 is how much more acidic than a pH of 5? 100 1000