2.2 Properties of Water
KEY CONCEPT
Water’s unique properties allow life to exist on
Earth.
2.2 Properties of Water
Life depends on hydrogen bonds in water.
1. Water is a polar molecule, meaning it has an unequal
distribution of charges
– Polar molecules have slightly charged regions
_
O
H
+
H
+
– Nonpolar molecules do not have charged regions
2.2 Properties of Water
2. Hydrogen bonds form between slightly positive
hydrogen atoms and slightly negative atoms, such
as oxygen.
the s
means
slightly
H bond
2.2 Properties of Water
3. cohesion
– property allows water molecules to stick to other
water molecules
– polarity (uneven distribution of charges) allows
water molecules to stick together
Ex: water beading on the hood of a car
2.2 Properties of Water
– cohesion causes water to have a high surface
tension
Ex: water strider, belly flop
2.2 Properties of Water
4. adhesion
– property allows water molecules to stick to other
molecules; is seen as capillary action
What living things
benefit the most from
adhesion?
plants
2.2 Properties of Water
2.2 Properties of Water
5. Water has a high specific heat
– property allows water to resist a change in temperature
– it takes a lot of energy to raise the temperature of
water one degree due to its high specific heat
2.2 Properties of Water
How is this
characteristic
beneficial to
ocean or lake
life?
2.2 Properties of Water
Many compounds dissolve in water.
6. Water acts as a solvent to dissolve other substances.
Ex: water will dissolve
- salt
- sugar
- drink mixes
solution
2.2 Properties of Water
Some compounds form acids or bases.
- acids release H+ (hydrogen ions) when added to a solution
- have a pH less than 7
stomach acid pH between 1 and 3
more acidic
2.2 Properties of Water
- bases/alkalines remove H+ (hydrogen ions) from a solution
– have a pH greater than 7
bile pH between 8 and 9
more basic
2.2 Properties of Water
• A neutral solution has a pH of 7
pure water pH 7
2.2 Properties of Water
- pH measures how acidic (an increase in H+ content) or
how basic (a decrease in H+ content) a substance is
2.2 Properties of Water
- the pH scale range is from 0 to 14
acids
more acidic
bases
more basic
(alkaline)
2.2 Properties of Water
Living organisms contain chemicals called buffers to help
them maintain a constant pH
strong acid
weaker acid
+
+
weak base
water
2.2 Properties of Water
strong acid + weak base
(reactants)

weaker acid + water
(products)