Biology CP
Notes: The Properties of Water
Chemical Formula:
Name:
Structural Formula:
Bohr model diagram:
Water is neutral (like other molecules) because
Polarity
Draw the subatomic particles of the nucleus of
each atom in the boxes at the right.
Hydrogen
Oxygen
When comparing the nucleus of an oxygen atom and a hydrogen atom, which one would have a
stronger attraction for electrons? Why?
At any moment, there is a greater likelihood of finding the shared electrons in water close to its
oxygen atom than either of the hydrogen atoms. As a result, the oxygen end of the molecule
has a slight _____________ charge and the side of the molecule with the hydrogen atoms has a
slight ___________ charge. This means that water is a polar molecule. Note that these partial
charges are weaker than the charges on ions such as Na+ or Cl-.
polar:
Polar Covalent
Bond
Polar Covalent
Bond
Kind of like the
poles of earth!
1
Hydrogen Bonding
Polar molecules (such as water) can attract each other because of
their partial (+) and (-) charges.
____________________________: the attractive force between the hydrogen in a polar
molecule and the oxygen or nitrogen in another polar molecule
Hydrogen bonds are weaker than covalent or
ionic bonds.
Water is able to form multiple hydrogen
bonds, which account for many of water’s
special properties.
How many hydrogen bonds
Are shown in the picture to the right?
Hint: look carefully!
Water’s special properties
1.
: An attraction between molecules of the same substance.
This causes water molecules to be drawn together.
Examples:
2.
: An attraction between molecules of different substances.
Examples:
3.
: The amount of heat energy required to raise the temperature of a
substance. Water’s heat capacity is unusually high.
Examples:
2
4.
: The amount of mass per unit volume. (D = m / v). Solid water (ice)
has a lower density than liquid water.
Examples:
5. Water is known as the ______________________________: In reality, water can’t
dissolve everything…but water is an excellent solvent, and it’s especially common in and
around living things.
Solution
Solvent
Solute
What are some substances that water can easily dissolve?
Water’s polarity gives it the ability to act as an excellent solvent because it can dissolve both
______________ compounds AND other ______________ molecules. With polar solutes (like
sugar), water molecules surround and separate the polar molecules from each other. With ionic
solutes (like salt), water molecules surround and separate the individual ions from each other, a
process known as dissociation.
How Salt Dissolves in Water
3
2.2 Properties of Water
The Water Molecule
For Questions 1–4, write True or False on the line provided.
1. Water is a polar molecule.
2. Hydrogen bonds are an example of adhesion.
3. Covalent bonds give water a low heat capacity.
4. A hydrogen bond is stronger than a covalent bond.
Write your answers in the spaces provided.
5. Compared to most other substances, a great deal of heat is needed to raise the
temperature of water by a given amount. This is because water….
6. Explain the distribution of partial charges in a water molecule.
7. Explain the difference between cohesion and adhesion.
8. Which is more dense – ice or water? How do you know?
9. Explain the difference between how water dissolves a sugar vs. a salt.
10. Explain the difference between the following terms: Hydrogen Bond and Covalent Bond
4