Objectives:
✓ Know the importance of hydrogen bonding to the properties of water
✓ Four unique properties of water and how they contribute to life on Earth
✓ Know how to interpret the pH scale
✓ Know the importance of buffers in biological systems
Concept: The polarity of water molecules result in hydrogen bonding
1. The structure of water is key to its special properties. Water is made up of _____
atom(s) of oxygen and ________ atom(s) of __________________.
2. Water molecules are _____________ which gives the end bearing the oxygen atom a
Slightly _________ charge and the hydrogen atoms are slightly ___________ charge.
3. ________________ bonds form between different water molecules.
4. Each water molecule can form a maximum of ________ hydrogen bonds at one time.
Concept: Four emergent properties of water contribute to Earth’s fitness for life
5. Water is so unique because of its hydrogen bonds:
✓ ___________________ is the linking of like molecules. Think of this
property as a “water strider” walking on the top of a pond due to the
____________ tension created by hydrogen bonding between water molecules.
✓ __________________ is the clinging of one substance to another. Think of
water adhering to another substance like the sides of a glass or a windshield.
✓ __________________ is the movement of water molecules up a very thin
tube called stomata and their evaporation from the stomates in plants. The water
molecules to each other by _______________ and the walls of the xylem by
_________________.
6. Moderation of _______________________ is possible because of a water’s high
specific heat.
✓ Specific heat is the amount of heat required to __________________ or
lower the temperature of a substance _______ degree Celsius. Relative to most
other materials, the temperature of water changes less when a given amount of
heat is lost or ___________________. The high specific heat of water makes the
Earth’s oceans relatively _________________ and able to support _________
quantities of life.
7. ___________________ of bodies of water by floating ice.
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✓ Water is less ____________ as a solid than a liquid which is opposite of most
other substances. Since ice is less ____________ it will float. This keeps large
bodies of water from __________________ and moderates the
_______________.
8. Water is an important ____________________. (A substance something dissolves in.)
✓ ______________ substances are water-soluble. These include IONIC
compounds, ____________ molecules like sugar and some proteins.
✓ ________________ substances like oils are nonpolar and will not
_______________ in water.
Concept: Acidic and basic conditions affect living organisms
9. The pH scale runs between _______ and __________ and measures the relative
____________ and ____________ of aqueous solutions. Draw the scale below and list
and example at each increase of 10 fold.
10. Acids have an excess of ________ ions and a pH below _________.
11. ____________ have an excess of _________ ions and a pH above __________.
12. Pure water is _______________ which means has a pH of _________.
13. Buffers are substances that minimize changes in the ______. The accept _______
from solution when they are in excess and donate _________ when they are depleted.
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