ch.2 biology #5: chemical basis of life cont.

salt & its properties

any ionic compound

• strong and hard when dry, dissolves easily in water

• may drugs are manufactured as salts

hydrogen bonds

weak bonds within and between polar molecules

hydrogen is most often attracted to…

oxygen and nitrogen

ion

atom with an electrical charge due to gain or loss of electrons

in each h2o molecule, hydrogen can bond up to how many partners

4

what kind of molecule is water

polar

• water forms polar covalent bonds

chemical reaction

breaking existing chemical bonds and forming new ones

balanced chemical eqn

same number of atoms on both sides

life supporting properties of water

• cohesion

• adhesion

• surface tension

cohesion

tendency of molecules of the same kind to stick together due to hydrogen bonds

adhesion

clinging of one substance to another

surface tension

measure of how difficult it is to stretch or break the surface of a liquid

thermal energy

energy associated with the random movement of atoms and molecules

heat

thermal energy transferring from a warmer body of matter to a cooler body of matter

temperature

measure of intensity of heat. avg speed of molecules in a body of matter

what bonds must be broken to allow molecules to move more quickly

hydrogen bonds

how do you break hydrogen bonds

heat must be absorbed

• water absorbs large amt of heat to break its bonds

• when water cools it releases a lot of heat

what does water do for the earth

helps keep temperature of planet within limits that permit life

• eg. summer, water stores heat

• winter, water releases stored heat

• stabilizes ocean temps for marine life

evaporation

change of a substance from liquid to a gas

evaporative cooling

liquid that remains after evaporation is, on average, cooler than before