15.1. Properties of Water http://www.ck12.org
Lesson Summary
- Water is a molecular compound consisting of polar molecules that have a bent shape. The oxygen atom
acquires a partial negative charge, while the hydrogen atoms acquire partial positive charges. - Hydrogen bonding between water molecules is responsible for its high surface tension, low vapor pressure,
and high melting and boiling points relative to other molecular substances with similar molar masses. - The rigid hydrogen bonds in ice form an open network that causes the solid form of water to be less dense
than its liquid form. As a result, ice floats in liquid water.
Lesson Review Questions
Reviewing Concepts
- What is the shape of a water molecule?
- What physical property of an element determines whether it acquires a positive or negative partial charge when
participating in a polar covalent bond? - How many hydrogen bonds is each water molecule capable of making?
- Why is ice less dense than water?
- Discuss the environmental consequences if ice were denser than water.
- How does the vapor pressure of water at a given temperature compare to that of other substances with similar
molar masses? Explain. How does this affect the rate of evaporation of bodies of water?
Problems
- Use the table above (Table15.1) to answer the following.
a. What is the volume of 100.0 g of water at 100°C?
b. What is the volume of 100.0 g of water at 4°C?
c. What is the volume of 100.0 g of water at 0°C?
d. What is the volume of 100.0 g of ice at 0°C? - A completely full bottle of boiling water is placed in the freezer. Discuss what happens as the water cools and
eventually freezes. - Explain which property of water is responsible for each of the following phenomena.
a. An asphalt road breaks apart as water seeps into small cracks and freezes.
b. A bottle of gasoline evaporates more quickly than a bottle of water.
c. Water forms nearly spherical drops as it slowly drips out of a faucet.
Further Reading / Supplemental Links
- Walter Wick,A Drop of Water: A Book of Science and Wonder. Scholastic Press, 1997.
- TheHydrogenBond, (http://www.wisc-online.com/Objects/ViewObject.aspx?ID=GCH1004
- Yves Marechal,The Hydrogen Bond and the Water Molecule: The Physics and Chemistry of Water, Aqueous
and Bio Media. Elsevier Science, 2006. - John Gregory,Particles in Water: Properties and Processes. CRC Press, 2005.