Chemistry Notes # 6
NOTES Chapter 2 section 2 - WATER
H2O
Polarity
Molecule – more than one atom
Compound – more than one type of element
O has 1 covalent bond with each H
O has a stronger electronegativity than H causing an unequal sharing of
electrons
O has the e- more often, so it has more of a negative charge; H has
more of a positive charge
Polar molecule is a molecule where charges are unevenly distributed.
WEAK bond between molecules
Hydrogen
Bonds
(Not between atoms to create a molecule, that’s covalent and ionic)
Hydrogen is often partially positively charged and makes weak bonds
with partially negatively charged areas of other molecules.
H2O molecules sticking together;
the H+ area of one atom attracting
the O- areas of a different atom
Cohesion
Adhesion
Same type of molecule attracted to each other
Ex: H2O droplets stick together, Insects walk on water surface.
Different types of molecules attracted to each other
Stronger than Cohesion
Ex: Minescus – H2O sticks to the glass
Ex: Capillary Action – H2O rises in a narrow tube against gravity.
This is how water gets from the roots of a plant to the leaves.
Chemistry Notes # 6
Mixture
2 or more substances physically mixed, but NOT chemically combined
(so NOT H2O, H is chemically bonded to the O)
Ex. Earth’s atmosphere is a mixture of gases
Solution – Homogeneous mixture (one sub is dissolved in another)
 mixture where solute (ex: salt) is dissolved in the solvent (ex:
water)
 H2O is the greatest solvent in the world
 Particles are evenly distributed
Suspension -Mixture that is not dissolved but remains suspended
Ex. Sand in water, blood with cells
pH Scale
Acids
0
H 2O
pH
neutral
The concentration of H+ ions
(parts hydrogen or percent hydrogen)
Bases
7
more H+ions
less OH- ions
14
less H+ ions
more OH- ions
Each step is 10X more or less concentrated than the previous step.
EX: pH 4 has
pH 3 has
pH 2 has
pH 5 has
pH 6 has
10
_____
_____
_____
_____
H+ ions
H+ ions
H+ ions
H+ ions
H+ ions
Acid is a compound that forms H+ ions in solution
Base is a compound that forms OH- ions in solution
Buffers – weak acids or bases that help maintain homeostasis.
They react with strong acids or bases to prevent sharp sudden changes
in pH.