Chapter 4
Physics of Matter
Matter: Phases, Forms & Forces
Matter is anything that has mass and occupies space.
We classify matter into four categories:
Solid: rigid; retain its shape unless distorted by a force
Liquid: flows readily; conforms to the shape of a container; has a
well-defined boundary; has higher densities than gases
Gas: flows readily; conforms to the shape of a container; does not
have a well-defined surface; can be compressed readily
Plasma: has gaseous properties but also conducts electricity;
interacts strongly with magnetic fields; commonly exists at higher
temperatures.
The chemical elements represent the simplest and purest forms of
everyday matter.
Each element is composed of incredibly small objects called atoms.
Every atom has a very dense, compact core called the nucleus.
The nucleus is composed of two kinds of particles:
Protons: have a positive electric charge
Neutrons: have no electric charge
The nucleus is surrounded by one or more particles called electrons.
Electrons have the same electric charge as protons but are
negatively charged.
Behavior of atoms and molecules
* The constituent particles of atoms and molecules exert electrical
forces on each other.
* The nature of these forces determines the properties of the
substance.
* We can relate the three common phases of matter to the
interparticle forces as follows:
Solids: Attractive forces between particles are very strong; the
, atoms or molecules are rigidly bound to their neighbors and can only
vibrate.
Liquids: The particles are bound together, though not rigidly; each
atom or molecule move about relative to the others but is always in
contact with other atoms or molecules.
Gases: Attractive forces between particles are too weak to bind
them together; atoms or molecules move freely with high speed and
are widely separated; particles are in contact only when they collide.
Atoms or molecules in a solid arranged in a regular geometric
pattern are called crystals.
Solids that do not have a regular crystal structure are called
amorphous solids.
Carbon has two common crystalline forms.
1- Graphite forms crystalline sheets with little bonding between
sheets.
2- Diamond forms very strong bonds between adjacent carbons —
it’s the hardest known natural substance.
liquids, the inter-atomic forces are insufficient to bind the atoms
rigidly. The atoms are free to move and vibrate.
gases, the inter-atomic forces are virtually negligible unless the
atoms are very close.Gaseous atoms have rather high speeds:
~1,000 mph. Whenever a high-speed gas atom impacts a large force
on a container. It is this force that produces a pressure on the
container.
As the air molecules strike the inside of a tire, they produce the
pressure that inflates the tire. If the molecules are stationary, there
is no pressure.
Gases are easily compressed because the majority of their volume is
the space between the atoms. If you compress it enough, you force
the atoms close enough together that you form a liquid.
Pressure
Pressure is the force per unit area for a force acting perpendicular to
a surface. pressure is a scalar.
Physics of Matter
Matter: Phases, Forms & Forces
Matter is anything that has mass and occupies space.
We classify matter into four categories:
Solid: rigid; retain its shape unless distorted by a force
Liquid: flows readily; conforms to the shape of a container; has a
well-defined boundary; has higher densities than gases
Gas: flows readily; conforms to the shape of a container; does not
have a well-defined surface; can be compressed readily
Plasma: has gaseous properties but also conducts electricity;
interacts strongly with magnetic fields; commonly exists at higher
temperatures.
The chemical elements represent the simplest and purest forms of
everyday matter.
Each element is composed of incredibly small objects called atoms.
Every atom has a very dense, compact core called the nucleus.
The nucleus is composed of two kinds of particles:
Protons: have a positive electric charge
Neutrons: have no electric charge
The nucleus is surrounded by one or more particles called electrons.
Electrons have the same electric charge as protons but are
negatively charged.
Behavior of atoms and molecules
* The constituent particles of atoms and molecules exert electrical
forces on each other.
* The nature of these forces determines the properties of the
substance.
* We can relate the three common phases of matter to the
interparticle forces as follows:
Solids: Attractive forces between particles are very strong; the
, atoms or molecules are rigidly bound to their neighbors and can only
vibrate.
Liquids: The particles are bound together, though not rigidly; each
atom or molecule move about relative to the others but is always in
contact with other atoms or molecules.
Gases: Attractive forces between particles are too weak to bind
them together; atoms or molecules move freely with high speed and
are widely separated; particles are in contact only when they collide.
Atoms or molecules in a solid arranged in a regular geometric
pattern are called crystals.
Solids that do not have a regular crystal structure are called
amorphous solids.
Carbon has two common crystalline forms.
1- Graphite forms crystalline sheets with little bonding between
sheets.
2- Diamond forms very strong bonds between adjacent carbons —
it’s the hardest known natural substance.
liquids, the inter-atomic forces are insufficient to bind the atoms
rigidly. The atoms are free to move and vibrate.
gases, the inter-atomic forces are virtually negligible unless the
atoms are very close.Gaseous atoms have rather high speeds:
~1,000 mph. Whenever a high-speed gas atom impacts a large force
on a container. It is this force that produces a pressure on the
container.
As the air molecules strike the inside of a tire, they produce the
pressure that inflates the tire. If the molecules are stationary, there
is no pressure.
Gases are easily compressed because the majority of their volume is
the space between the atoms. If you compress it enough, you force
the atoms close enough together that you form a liquid.
Pressure
Pressure is the force per unit area for a force acting perpendicular to
a surface. pressure is a scalar.
