Water
Probably
the most important
compound in organisms
water makes up 70 - 95% of
most organisms
allows
molecules to move
and interact with one
another
transports materials in
plants and animals (blood,
plant sap)
Water is polar
Polar molecule - molecule
with an unequal
distribution of charge
has a negative end and a
positive end
Charged
ends of water
molecules are attracted to
each other
the attraction of opposite
charges of hydrogen and
oxygen atoms forms a weak
bond - hydrogen bond
Water is cohesive
Water is held together by
hydrogen bonds
drop holds together
water being soaked up pulls
more water up with it
Water
resists temperature
change
water requires high heat
to increase its temperature
Why is this important
to cells?
Water
helps cells maintain
a steady environment
(homeostasis)
Mixtures
• Mixture
- combination of
substances in which each
substance retains its own
properties
• ex. Salt and pepper
• Solution
- a mixture in which
one or more substances is
dissolved in another
substance
• evenly distributed
• ex. Sugar dissolved in water
• Solute
- substance that is
dissolved
• ex. Sugar (Kool-Aid)
• Solvent - substance in which
the solute is dissolved
• ex. water
Acids and bases
• pH
- measure of how acidic
or basic a solution is
• pH ranges from 0(most
acidic) to 14 (most basic)
• 7 is neutral
• Acid
- substance that forms
+
hydrogen ions (H ) in water
• Hydrochloride (HCl) forms
+
H and Cl ions in water
• hydrochloric acid
• Acids
have a pH below 7
• Base - substance that forms
hydroxide ions (OH ) in
water
• Sodium hydroxide (NaOH)
+
forms Na and OH ions in
water
• Bases
have a pH above 7
Acid or base
Ammonia
(Windex)
Base (pH 11)
Vinegar
Acid (pH 3)
Egg
Base
(pH 8)
Tomato
Acid (pH 4)
Milk
Acid (pH 6)
Water
(pure)
Neutral (pH 7)