Solids, Liquids and Gases
States of Matter
• matter – anything that has mass & takes up space
• there are 4 states of matter that depend on TEMPERATURE
• solid – has a definite shape & volume
• liquid- has a definite volume, but no definite shape
• gas – has no definite volume or shape
• plasma- made of high energy, electrically charged particles, found on
the sun
• most common type of matter in the universe (99% of mass in solar system)
• it is a gas like mixture of positive & negative charged particles
• it is seen when fluorescent lights are turned on & the electricity causes particles
of mercury gas to form plasma
Kinetic Theory of Matter
• all matter is made of tiny particles in constant motion
• the higher the temperature, the faster the motion
• the motion & spacing (due to temperature) determines the state
of matter
Kinetic Theory of Solids
• particles are packed very close & held together by forces between
particles
• particles move back & forth, but don’t change positions
• most solids form crystals – particles arranged in a repeating pattern
• different solids have different crystal shapes
• amorphous solids – materials that appear solid but don’t have a
crystal structure
• amorphous means “having no form”
• ex) glass, butter, wax
• can be classified as ‘thick liquids’
Kinetic Theory of Liquids
• particles are very close together, but can move past each
other
• liquids can pour easily (water), slowly (syrup), or hardly at
all (tar)
• viscosity- a property of a liquid that describes how it pours
• tar is very viscous, water isn’t
Kinetic Theory of Gases
• particles have a lot of energy, and can go
everywhere
• particles move in a straight line all over their
container
• particles only change direction when they hit other
particles or wall of their container
• a gas is mostly EMPTY SPACE
Thermal Expansion
• thermal expansion – the increase in the volume of matter as the temperature
increases
• when energy is added, thermal energy increases the kinetic & potential energy
of the particles and
• they move faster, collide more often & collide harder
• because they hit each other harder they bounce off harder, move farther apart
& increase the volume of the matter
• expansion joints- gaps in building structures & streets that allow material to
expand in hot weather and shrink in cold weather without cracking
Changing States of Matter
• any change in the state of matter is a PHYSICAL change, not chemical
• melting point- the temperature at which a solid becomes a liquid
• freezing point- the temperature at which a liquid becomes a solid
• boiling point- the temperature at which a liquid becomes a gas (vaporizes)
• condensation – the process that occurs when a gas cools & becomes a liquid
• sublimation – a change from a solid to a gas without becoming a liquid
• dry ice (solid CO2) and iodine have no liquid state at normal air pressure
• deposition- change from a gas to a solid
frost- change of water vapor in the air to water crystals
• evaporation – the change from a liquid to a gas without boiling
• vaporization- the change from a liquid to a gas at the boiling point
Nature of Gases
Pressure
pressure- the amount of force per unit area
-gases exert forces on everything!
-pressure does not depend on the size of the surface it presses on
_____
pressure force
area
Newton – The SI unit for force
Pascal – the SI unit for pressure , it equals 1 N
m2
Why do gases exert pressure?
Gases exert pressure because:
they are in constant motion and as they move
about they hit the surfaces of the container, and
every time they hit the sides they exert a tiny
pressure and it is the combined effect of ALL the
particles constantly bouncing off the surface that
cause air pressure
• Air pressure is caused by all the particles of air that are
constantly bouncing off of us and the earth’s surface, at
1610 km/hr
• There is less air pressure at higher altitudes because
there are less particles, so there are less collisions
which means there is less pressure
Boyle’s Law
• It states: “The pressure of a gas will increase as the volume
of a gas decreases provided the temperature does not
change”
• WHY? Because particles will move as fast in a smaller area &
will collide more often causing an Increase in pressure
Charles Law
• It states: “ If a sample of gas is kept at constant pressure, the volume increases,
if temperature increases.”
• WHY? When energy is added, the particles move faster, hit each other & sides of
container harder and more often which can cause the walls of the container to
bulge
• 4 factors needed to describe a gas:
•
•
•
•
mass
volume
pressure
temperature
Fluids
Archimedes Principle
• it states: “the buoyant force on an object that is submerged in fluid is equal
to the weight of the fluid displaced by that object”
• when objects are in water they displace an amount of water equal to the
volume of the object
• buoyant force- the upward force of a fluid on an object
• if the buoyant force is LESS than gravity the object sinks, if it is MORE than
gravity it floats
• dense fluids like salt water, exert a larger buoyant force than less dense fluids
Pascal’s Principle
• it states: “the pressure applied to a fluid is transmitted
unchanged throughout the fluid”
• if you dive into a pool, the pressure is the same on all parts
of your body & the only factor that affects the pressure is
how deep you dive
• hydraulic lifts are used to lift heavy loads because it
multiplies a force
Bernoulli’s Principle
• it states: “ the pressure of a moving fluid is HIGH when the velocity
is LOW, and the pressure is LOW when the velocity of it is HIGH
• -deals with fluids that are moving (liquids & gases)
• -fluids move from areas of high pressure to low pressure
• -fluids move when there is a difference in pressure between 2
regions
• -it explains why a pitched ball curves – the pitcher gives it a sideways
spin around a vertical axis as it moves through the air; the air moves
faster past the side spinning forward therefore the air pressure is
lower
• also explains what helps keep planes in the air,
• their wings are designed so that the air must travel further over the top of the
wing than over the bottom;
• the air takes the same amount of time over both sides of the wings but it has
to move faster on top so there is less air pressure on top of the wing and a
greater pressure on the bottom of the wing
• Venturi effect- when a moving fluid is forced to travel in a narrower path, its
velocity increases
Heat of Fusion and Heat of Vaporization
• heat of fusion- the energy needed to change from the solid state to the liquid
state
• heat of vaporization – the energy needed to change from a liquid to a gas
• energy causes the temperature of a substance to rise to the freezing/melting
point; at that point the temperature no longer rises because all the energy
goes into breaking apart the particles of ice;
• when the ice is now all water the energy causes the temperature to rise again
until it reaches theboiling point
• Boyle’s Law
• Charles Law