Content Benchmark P.8.A.1
Students know particles are arranged differently in solids, liquids, and gases of the same
substance. E/S
Matter makes up every object, material, and substance in the universe and is composed of
building blocks known as atoms. A more careful definition of matter is anything that has both
mass and volume. Mass is the quantity of matter in an object, while volume is the amount of
space the object occupies. Mass and volume are physical properties, but both physical and
chemical properties identify matter. For example, all materials exist in various states.
Figure 1. Boiling liquid water is thrown into the extremely cold air creating clouds of steam and a
shower of ice crystals. On Earth, water can exist as a solid, liquid and gas at the same time.
(From http://www.waterencyclopedia.com/En-Ge/Fresh-Water-Physics-and-Chemistry-of.html)
These different states are determined by the amount of energy present in the system. Energy is
the ability to do work or cause change, and is found in several forms, but kinetic energy is the
form that is most valuable in terms of explaining what happens to a state of matter as it is
changed from one to another. Within the various states of matter particles are in a constant
motion. In liquids and gases, this motion is known as the Brownian motion, where particles
move randomly while suspended in a fluid. Even in solids, molecules continually move.
Generally, the movement in solids is a vibration around a fixed point and not the more free
flowing movement of Brownian motion found in liquids and gases.
To learn more about Brownian motion and the states of matter, go to
http://www.aip.org/history/einstein/essay-brownian.htm.
It then is essentially the rate of movement of particles that determines the state of a substance.
Energy must then be added (or removed) for a substance to change state. Increasing or
decreasing the amount of kinetic energy present in the substance determines whether or not it is
referred to as a solid, liquid, gas, or plasma. Water is one substance on Earth that commonly
exists as a solid (commonly called ice), liquid (commonly referred to as water), and gas
(commonly called water vapor). Each individual state will be discussed in more detail below.
Figure 2. Phases of Matter represented by the type of molecular motion found at different temperatures.
(From http://itl.chem.ufl.edu/2045_s00/lectures/lec_f.html)
Figure 3. Example of a phase diagram – a plot that illustrates the phases of a
substance in relation to the pressure and temperature.
(From http://astronomy.swin.edu.au/cms/imagedb/albums/userpics/sublimation1.jpg)
Solids have a definite shape and fixed volume. Within a solid, the molecules are tightly packed,
held in relatively fixed positions, and have little kinetic energy. The intermolecular forces and
strength of bonds within a solid are what enable particles to be held in relatively fixed positions.
To view an example of a solid retaining its shape and volume, go to the link below which shows
the molecular structure of water ice crystals.
http://www.visionlearning.com/library/module_viewer.php?mid=120
(scroll down to the visualization that shows water ice.)
Liquids have weaker molecular bonds than those of solids and allow molecules to move more
freely within the substance. Similar to solids, liquids have a fixed volume. However, because the
intermolecular forces are weaker than solids, liquids will take the shape of their container,
assuming the liquid is under the influence of gravity. Television is a great source to see the
physical properties of liquids with all of the commercials demonstrating the absorbent ability of
certain materials, such as paper towels. Usually in these commercials, liquids freely flow across
a surface, and continue to do so, until the liquid reaches a barrier. Liquids flow because they
lack a definite shape. For a given substance, the internal molecular motion is greater in a liquid
than a solid, and therefore, the average molecular kinetic energy is greater in a liquid than in a
solid.
In the example animation below, we see that liquid water is made up of molecules that move
relatively freely, yet remain relatively close in distance to each other.
http://www.visionlearning.com/library/module_viewer.php?mid=120
(scroll down to the simulation that shows liquid water.)
Gases are a third state of matter, and compared to solids and liquids, have weak intermolecular
forces. Because of their relatively weak molecular forces, gases move rapidly through space and
have a relatively high average molecular kinetic energy. Gases have no definite volume or shape,
and therefore, fill a container and take the shape and volume of that container. In order for liquid
water to become water vapor—a gas—energy must be transferred into the liquid, raising the
average kinetic of the water molecules, allowing the water to boil, and change its state to a gas.
Similar to water vapor, steam is also water in the gaseous state, but unlike water vapor, the
temperature of steam is greater than the boiling point.
To view an example simulation of the behavior of water molecules entering the gas state, go to
the link below
http://www.visionlearning.com/library/module_viewer.php?mid=120
(scroll down to the visualization showing steam.)
The following table is good summary of the differences between solids, liquids, and gases when
examined at the microscopic level.
Some Characteristics of Gases, Liquids and Solids and the Microscopic
Explanation for the Behavior
(From: http://www.chem.purdue.edu/gchelp/atoms/states.html)
gas
Liquid
Solid
assumes the shape and
volume of its container
particles can move past one
another
assumes the shape of the
part of the container which
it occupies
particles can move/slide
past one another
retains a fixed volume and
shape
rigid - particles locked into
place
compressible
lots of free space between
particles
not easily compressible
little free space between
particles
not easily compressible
little free space between
particles
flows easily
particles can move past one
another
flows easily
particles can move/slide
past one another
does not flow easily
rigid - particles cannot
move/slide past one
another
To learn more about the states of matter, including the particle arrangements within each state,
relative kinetic energy quantities between the states, and how matter changes state, go to
http://www.chemtutor.com/sta.htm.
Content Benchmark P.8.A.1
Students know particles are arranged differently in solids, liquids, and gases of the same
substance. E/S
Common misconceptions associated with this benchmark
1. Students incorrectly believe that materials can only exhibit properties of one state of
matter.
Water is unique in that it is the only natural substance that is found in all three states— liquid,
solid (ice) and gas (water vapor and steam) –at the temperatures normally found on Earth’s
surface. Earth's water is constantly interacting, changing, and in movement. However, students
think of water only in its liquid form, and fail to understand that water can also be a solid (ice) or
gas (water vapor and steam). Students can work through this misconception, by doing
investigations with water as the substance changes temperatures. For example, students may
measure the temperature of ice, where the ice is located on a beaker and hot plate. As energy is
transferred from the hot plate to the water, they can continue to measure temperature of the water
as it changes phase. When the water begins to boil, they can they take the beaker off of the hot
plate and measure the temperature decease. When the water become cooler, the students can
place the beaker in a freezer, again taking temperatures and noticing changes in state as the water
freezes. If the students mass the ice at the beginning and end of the experiment, they can
postulate that some of the water mass was lost to the environment as steam and water vapor.
To learn more about this misconception, go to
http://beyondpenguins.nsdl.org/issue/column.php?date=August2008&departmentid=professional
&columnid=professional!misconceptions.
2. Students inaccurately assume that gases are not matter because most are invisible.
Oxygen is a gas found in our atmosphere that is colorless and odorless. But oxygen is required
for us to live. Indeed, all the gases comprising a pollution-free atmosphere are colorless and
odorless. Because atmospheric gases are colorless and odorless, students believe that gases are
just empty space (e.g., a vacuum) and are not matter. However, students can become aware that
gas is matter by having them conduct experiments and view demonstrations showing that gases
have mass and take up space (i.e., fill a volume). If this is the basic definition of all matter, then
students can begin to understand that matter is not just empty space.
Further support concerning this misconception can be found at
http://www.chem1.com/acad/webtext/gas/gas_1.html.
3. Students have difficulty understanding that particles of solids have motion.
Solids are formed when the attractive forces between individual molecules are greater than the
energy causing them to move apart. Individual molecules are locked in position near each other,
and cannot move past one another. The atoms or molecules of solids remain in motion. However,
that motion is essentially limited to vibrational energy; individual molecules stay fixed in place
and vibrate next to each other. As the temperature of a solid is increased, the amount of vibration
increases, but the solid retains its shape and volume because the molecules are locked in place
relative to each other. Students should be allowed to view microscopic images that
demonstrating particle movement within solids. Other experiments with solids can reinforce that
molecular movement occurs in solids, specifically by looking at substances that have some solid
properties and some liquid properties (e.g., silly putty or “oobleck”)
More information about this misconception can be found at
http://www.chem.purdue.edu/gchelp/atoms/states.html.
4. Students have difficulty understanding that mass and volume, both describing an
"amount of matter,” are not the same property.
Mass is a measure of the quantity of matter present in an object. Volume is a measure of how
much space it occupies. Mass can be measured on an instrument called a balance—that is, the
object whose mass is sought is placed on one side of a see-saw like device and smaller reference
masses (objects) are placed on the other side until the balance swings freely at equilibrium. The
volume of an object can sometimes be determined by measurement of its various dimensions
followed by a calculation of its volume based on a suitable formula. For example, a box has a
volume that is the product of its length, width, and height, V = L×W×H. Volume of irregular
solid objects can also be measured by the amount of water displaced by the object. It would be
incorrect to assume that any small object is of low mass—and just as incorrect to assume that
any large object is of high mass. The concept of density is at the heart of this issue.
For more details about this misconception, go to
http://www.edinformatics.com/math_science/mass_volume_density.htm.
Content Benchmark P.8.A.1
Students know particles are arranged differently in solids, liquids, and gases of the same
substance. E/S
Sample Test Questions
Questions and Answers to follow on separate document
Content Benchmark P.8.A.1
Students know particles are arranged differently in solids, liquids, and gases of the same
substance. E/S
Answers to Sample Test Questions
Questions and Answers to follow on separate document
Content Benchmark P.8.A.1
Students know particles are arranged differently in solids, liquids, and gases of the same
substance. E/S
Intervention Strategies and Resources
The following is a list of intervention strategies and resources that will facilitate student
understanding of this benchmark.
1. Solid, Liquid, Gas Interactive Applets
The British Broadcasting Corporation has produced “KS2 Bitesize Revision.” This site includes
curriculum content, interactive simulations, and classroom lessons, which present a perspective
on the states of matter.
This site is found at http://www.bbc.co.uk/schools/ks2bitesize/teachers/lesson_plans/gases.shtml.
The matter unit has two modules that relate to (1) gases, liquids and solids and (2) solids and
liquids, both which specifically relate to this benchmark. The direct links to these two interactive
applets are:
 Gases, Liquids, and Solids
http://www.bbc.co.uk/schools/ks2bitesize/science/activities/gases.shtml.

Solids and Liquids
http://www.bbc.co.uk/schools/ks2bitesize/science/activities/solids_liquids.shtml.
2. The Atoms Family
The Science Learning Network and the Museum of Science, Inc. have developed a web page
devoted to educational activities relating to different forms of energy, presented by famous
gothic horror characters. The site contains a section focused on principles of atoms and matter.
This area allows the student to work through an interactive activity, which tests the student’s
knowledge of how the element or molecule changes phases at different temperatures in a
chamber.
The site can be found at http://www.miamisci.org/af/sln/phases/index.html.
3. States of Matter and Flight
NASA’s Glenn Research Center has an excellent site covering the physics of flight, called the
Beginner’s Guide to Aeronautics. Included at the site, is a concise discussion and interactive
Java™ applets, where students can do virtual experiments. This site also has excellent
information on force and motion and would be an appropriate resource for long-term review of
several physical science concepts in a single setting. To use this site, students will need access to
computers with Java™.
To access the states of matter section of this website, go to
http://www.grc.nasa.gov/WWW/K-12/airplane/state.html.
4. States of Matter Investigations
The University of California, San Francisco has created a series of hands-on, inquiry-based
investigations covering the states of matter. These lessons go over the basics of the properties of
matter, as well as investigations about the change of state. Each lesson has a listing of the
required resources needed to conduct the investigations, with background information for
teachers and students.
To download these lessons, go to http://seplessons.ucsf.edu/node/351.
5. Chemistry Visualizations
The MoreChemistry.com site has several visualizations that can be used to understand
fundamental chemistry better. Included are states of matter visualizations that students can use to
see how particle motion differs in each state for a given substance. One excellent visualization
shows what happens under very high temperature and high pressure situations that cannot be
simulated in a normal middle school classroom. In this way, students can relate these two
important properties to solids, liquids, and gases. To use this site, students will need access to
computers with Java™.
This site can be found at http://www.morechemistry.com/links/Applets_and_Visualizations.html
(make sure you scroll down to the states of matter link).