Chapter 2
States of Matter
Matter
n
Anything that
takes up space and has mass
– Composed of tiny particles
– What are they called????????
n
Three states of
matter:
– Solid, liquid, gas
n
Plasma is the
fourth state
– Occurs only at very high temperatures and is not
naturally common on Earth
Movement of Particles
n
Atoms are always
moving in matter
n
They move faster
when they have more kinetic energy (energy of movement) and slower when they have less kinetic
energy
n
More heat = More
energy
Solids
n
Matter with
definite shape and volume because particles are packed closely together and
merely vibrate in place
n
Very little
kinetic energy in particles
– So they move very slowly
n
Particles of
solids arranged in one of 2 ways:
– Crystals - arranged in repeating, 3-D patterns
–
Amorphous - have
random arrangement
Liquids
n
Matter with a
definite volume but no definite shape
– Particles move more freely than those of a solid
n
Particles have
more kinetic energy than particles in solid
– So they are moving faster than in a solid
n
Viscosity is a
liquids resistance to flow
– Increases when particles are more strongly attracted
to each other
n
Surface Tension
is the tendency of molecules of a liquid to stick together
–
Due to uneven
forces acting on particles
Gasses
n
Matter that does
not have a definite shape or volume
n
Diffusion is the
movement of particles from an area of high concentration to an area of low
concentration
– If you spray cologne, the smell will eventually spread
out.
– In about 7 years, your breath spreads out evenly over
the earth
n
Gas particles
spread out evenly and as far apart as possible
– They will fill a container.
n
Most kinetic
energy
– So they are moving the fastest
Plasma
n
Most common state
of matter in the universe
n
Plasma occurs
when gasses get so much heat/energy that the electrons are stripped from the
nuclei
– You end up with separate positive and negative
“clumps” and an overall neutral charge
n
Examples on Earth
– Neon signs
– Fluorescent bulbs
– VERY hot fire (lightning)
Changes of State
n
Particles are in
constant motion
– Amount of movement depends on their kinetic energy (energy
of movement)
n
Thermal energy is the total energy of all the particles in a sample
of matter
n
Temperature is the average kinetic energy of particles in a
substance
n
Heat is the movement of thermal energy from a substance
with a higher temperature to one with a lower temperature
Changes of State
n
Specific Heat is the amount of heat
needed to raise the temperature of 1 g of a substance 1°C
n
For example, the specific heat of water is equal
to one calorie
Changes of State
n
Matter can change
states as energy is absorbed or released
n
A change from the
solid to the liquid state is called melting
– Is energy absorbed or released?
– What happens to the particles?
n
A change from the
liquid to the solid state is called freezing?
– Is energy absorbed or released?
–
What happens to
the particles?
Changes of State
n
A change from
liquid to gas is called vaporization
n
Boiling is vaporization which occurs below the liquid’s
surface at its boiling point
n
Evaporation is vaporization which occurs at the surface of a
liquid
– Molecules must be at or near the surface at the right
speed to evaporate
– What about energy?
– What about particles?
Changes of State
n
Condensation is a
change from a gas to a liquid
– What about energy?
– What about particles?
n
During sublimation,
the surface particles of a solid gain enough energy to become a gas.
Pressure
n
Pressure equals the force exerted on a surface divided by the
total area over which the force is exerted
– Pressure(P) = Force(F) / Area(A)
n
If force increases
over an area, the pressure increases
n
If force over an
area decreases, the pressure decreases
Pressure
n
Atmospheric
pressure is the air that presses down
on the Earth with force
n
Pressure can be balanced
as the pressure pushing down equals the pressure pushing up
n
As altitude
increases, air pressure decreases
–
That’s why it’s
colder at higher altitudes
Gas Pressure in Containers
n
Gas pressures in
a closed container changes with volume and temperature changes
n
Decreasing volume
increases pressure
n
Increasing volume
decreases pressure
n
Increasing
temperature increases pressure
n
Decreasing
temperature decreases pressure
Boyle’s Law
n
At a constant
temperature, pressure times volume is a constant
–
They are
inversely related (as one goes up, the other goes down)
Charles and Gay-Lussac’s
Law
n
At a constant
pressure, Volume = a constant times temperature
– Volume and temperature are directly proportional (as
one goes up, the other goes up)
The Ideal Gas Law
n
Charles’ and Boyle’s Law Combined
– pV=nRT (n and R are
constants)
n
Pressure x Volume is proportional to Temperature
– pV~T
Density
n
Density is mass
divided by volume
– D = M/V
– It’s all about the love
n
An object will float
in a fluid that is denser than the object
n
An object with
the same density as the fluid will stay the same level in the fluid
n
An object will sink
in a fluid that is less dense than the object
Density and States of Matter
n
Which is more dense: ice, liquid water, or water vapor?
– As particles of water get more energy (from heat),
they move faster and spread apart more.
n
As particles move
faster, they spread apart and become less dense.
n
Where is the air
the least dense? Why?
n
The air particles
are farther apart at high altitudes and are less dense (due to pull of gravity)
Buoyant Force
n
An upward force
on an object immersed in a fluid
n
Archimedes’
principle states that the buoyant force on an object is equal to the weight of
the fluid displaced by the object
– If a boat displaces 10,000 N of water, then the
buoyant force upward from the water will be 10,000 N (it will seem 10,000 N
lighter)
Pascal’s Principle
n
When a force is
applied to a confined fluid, an increase in pressure is transmitted equally to
all parts of the fluid
n
Hydraulic
systems allow people to lift heavy
objects with relatively little force
n
When squeezed,
liquids will be pushed out of a force pump, a closed container with a
hole in it.