Chapter 2
States
of Matter
Matter
l
Anything that takes up space and has mass
l
Composed of tiny particles called atoms
l
Three states of matter:
l
Solid, liquid, gas
l
Plasma is the fourth state
l
Occurs only at very high temperatures and is
not common on Earth
Solids
l
Matter with definite shape and volume
because particles are packed closely together and merely vibrate in place
l
Very little kinetic energy in particles
l
Particles of solids arranged in one of 2
ways:
l
Crystals -
arranged in repeating, 3-D patterns
l
Amorphous - have random arrangement
Liquids
l
Matter with a definite
volume but no definite shape
l
Particles move more freely than those of a
solid
l
Particles have more kinetic
energy than particles in solid
l
Viscosity is a liquids
resistance to flow
l
Increases when particles are more strongly
attracted to each other
l
Surface Tension is the
tendency of molecules of a liquid to stick together
l
Due to uneven forces acting on particles
Gasses
l
Matter that does not have a definite shape
or volume
l
Gas particles spread out evenly and as far
apart as possible
l
Most kinetic energy
Changes of State
l
Particles are in constant
motion
l
Amount of movement depends
on their kinetic energy
l
Thermal energy is the total energy of all the particles in a sample of matter
l
Temperature is the average kinetic energy of particles in a substance
l
Heat is the movement of thermal energy from a substance with a higher
temperature to one with a lower temperature
Changes of State
l
Specific Heat
is the amount of heat needed to raise the temperature of 1 g of a substance 1°C
l
For example, the specific heat of water is
equal to one calorie
Changes of State
l
Matter can change
states as energy is absorbed or released
l
A change from the solid to
the liquid state is called melting
l
Is energy absorbed or
released?
l
What happens to the
particles?
l
A change from the liquid to
the solid state is called freezing?
l
Is energy absorbed or
released?
l
What happens to the
particles?
Changes of State
l
A change from liquid to gas
is called vaporization
l
Boiling is vaporization which occurs below the liquid’s surface at its boiling
point
l
Evaporation is vaporization which occurs at the surface of a liquid
l
Molecules must be at or
near the surface at the right speed to evaporate
l
What about energy?
l
What about particles?
Changes of State
l
Condensation is a change from a gas to a
liquid
l
What about energy?
l
What about particles?
l
During sublimation, the surface
particles of a solid gain enough energy to become a gas.
Pressure
l
Pressure equals the force exerted on a
surface divided by the total area over which the force is exerted
l
Pressure(P)
= Force(F) / Area(A)
l
If force increases over an area, the
pressure increases
l
If force over an area decreases, the
pressure decreases
Pressure
l
Atmospheric pressure
is the air that presses down on the Earth with force
l
Pressure can be balanced as the
pressure pushing down equals the pressure pushing up
l
As altitude increases, air pressure
decreases
l
That’s why it’s colder at higher altitudes
Gas Pressure in Containers
l
Gas pressures in a closed container changes
with volume and temperature changes
l
Decreasing volume increases pressure
l
Increasing volume decreases pressure
l
Increasing temperature increases pressure
l
Decreasing temperature decreases pressure
Buoyant Force
l
An upward force on an object immersed in a
fluid
l
Archimedes’ principle states that the
buoyant force on an object is equal to the weight of the fluid displaced by the
object
l
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)
Density
l
Density is mass divided by volume
l
D = M/V
l
It’s all about the love ♥
l
An object will float in a fluid that
is denser than the object
l
An object with the same density as the fluid
will stay the same level in the fluid
l
An object will sink in a fluid that
is less dense than the object
Pascal’s Principle
l
When a force is applied to a confined fluid,
an increase in pressure is transmitted equally to all parts of the fluid
l
Hydraulic systems
allow people to lift heavy objects with relatively little force
l
When squeezed, liquids will be pushed out of
a force pump, a closed container with a hole in it.