15.1. Properties of Water http://www.ck12.org
Introduction
Water is truly an amazing substance. It can exist in all three states under normal pressures and temperatures. At
room temperature, it is a tasteless, odorless, colorless liquid, although it exhibits a blue hue when present in large
volumes. Approximately 70% of the Earth’s surface is covered in water. For a small molecule, water molecules are
highly attracted to one another, due to particularly strong hydrogen bonds. This leads to a number of properties,
such as a relatively high surface tension. Unlike most other substances, water expands when it freezes. Water is also
able to absorb relatively large amounts of heat with only minimal changes in temperature. This can be seen on a
small scale, such as the coolant in your car, or on a larger scale, such as the more moderate climates in coastal areas.
The water in the oceans acts as a tremendous heat sink, which influences global weather patterns. The clouds that
form above lakes and oceans originate from the evaporation of lake and ocean water. They are byproducts of water’s
thermal regulating capacity. Additionally, water is not only found here on Earth; scientists have found evidence of
water on a number of extraterrestrial planets. In this lesson, we are going to take a look at this unique and important
substance.
Water, Ice and Steam
As we saw in theStates of Matterchapter, all substances can transform from one state to another, depending on the
temperature and pressure of the environment. The solid, liquid, and gaseous forms of water all play an important
part in our everyday lives.
FIGURE 15.1
Example 15.1
Which of the processes inFigure15.1 require the absorption of heat? Which release heat?
Answer:
Melting, sublimation, and evaporation absorb heat from their surroundings. Freezing, deposition, and condensation
release heat.