Outline # 2 Chemical Basis of Life

Water

- water had several unique properties due to its polarity A

Water is a Polar Molecule 1. happens in covalently bonded molecules 2. oxygen has a slightly negative charge and hydrogen has a slightly positive end 3. the electrons are unevenly shared; greater pull towards oxygen that creates charged ends 4. uneven sharing creates a polar molecule 5. this makes water very effective at dissolving ionic & other polar substances B. Hydrogen Bonding 1. holds water molecules together 2. positive region of one water molecule is attracted to negative end of another 3. because the atoms have not transferred an e-, hydrogen bond is weaker than ionic bond

it is strong enough to make water cling to itself 4

What type of bond is water?

covalent

Is the oxygen side positive or negative?

Negative

Greater pull to the ...

oxygen

What holds water molecules together?

hydrogen bonds

Is the hydrogen bond stronger than an ionic bond?

no it's weaker

what causes water's properties

Hydrogen bonding-

cohesion

: attractive force between same/similar substances

surface tension:

a property of liquids such that their surfaces behave
like a thin, elastic film

adhesion

: attractive force between unlike substances

"capillarity” or capillary action

combo of cohesion & adhesion allows water to move upwards inside
narrow cavities, going against gravity

water is like a heat sponge

heat capacity

then temp increases & phase changes after

bonds have been broken

why can water absorb so much heat

it's hydrogen bonds

why is ice is less dense than water

molecules of ice are less densely packed than liquid water

what is water called

universal solvent

what substances can dissolve in water

polar and ionic

aqueous solution

a solution where water is the solvent

solvent

dissolves solute

solute

dissolved in the solvent

buffer

substance that causes solution to resist changes in pH

hydronium ions

made from taking protons

hydroxide ions

made from giving protons

an acid solution has more

hydroxide ions than hydronium

concentration

amount of solute dissolved in a fixed amount of the solution

when water dissociates it forms

H+ and OH-