2.1. Properties of Matter http://www.ck12.org
FIGURE 2.3
The particles of a gas are very far apart
compared to the particles of a liquid or a
solid.the particles that make up solids and liquids. Gases, like liquids, are fluids. Gases are easily compressed because of
the large spaces in between gas particles. The term gas is most often used to refer to a substance that is found in the
gas state at room temperature, such as hydrogen and nitrogen. However, substances that are solids or liquids at room
temperature can also evaporate into the gaseous state. Avaporis the gaseous state of a substance that is a solid or
liquid at room temperature. Examples include water vapor or sodium vapor (Figure2.4).
FIGURE 2.4
Sodium vapor lamps glow with a distinc-
tive yellow color.For a summary of the phases of matter, visit http://www.chem.purdue.edu/gchelp/atoms/states.html.
A fun, interactive simulation about phases of matter can be downloaded at http://www.concord.org/activities/states-matter
.
Another interactive simulation that will help you understand solids, liquids, and gases can be found at http://phet.
colorado.edu/en/simulation/states-of-matter. A variety of activity guides can be found by scrolling down.
NASA provides diagrams and explanations of states of matter at http://www.grc.nasa.gov/WWW/k-12/airplane/st
ate.html
NASA explains properties of gases in an informative website at http://www.grc.nasa.gov/WWW/k-12/airplane/ga
sprop.html.
Physical Changes
As an ice cube melts and it acquires the ability to flow, its shape changes. However, its composition does not change.
Melting is an example of a physical change. Aphysical changeis a change to a sample of matter in which some
properties of the material change, but the identity of the matter does not. Physical changes can further be classified as
reversible or irreversible. The melted ice cube may be refrozen, so melting is a reversible physical change. Physical
changes that involve a change of state are all reversible. Other changes of state include vaporization (liquid to gas),