SOLIDS, LIQUIDS,

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CHAPTER 2

• SOLIDS, LIQUIDS, GASES

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I. States of Matter -
matter can exist in the universe in 4 states or
phases - solid, liquid, gas, plasma

• A. Solids - have definite volume definite
  shape

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1. Particles in a solid - are packed
tightly together - stay in fixed
positions - shape - are hard to separate
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• In a solid, the molecules are tightly bound
  together -
• which holds a shape.
• They vibrate in place

(Molecular Motion)
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2. Types of Solids

• a. Crystalline solids - particles form regular
  repeating patterns

Iron pyrite
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- ex.s sugar, salt, sand, snow

• Melting point - the distinct temp. at which a
  crystalline solid melts.

The crystal structure of snow
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The molecular structure of salt a
microphotograph of salt crystals.
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b. Amorphous Solids

• Particles are not arranged in regular patterns.
• Do not have distinct melting point temperatures
  (just get softer softer)
• behave like slow moving, super-cooled liquids

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- Can lose their shape under certain
conditions Ex.s - plastics, rubber, glass, wax,
tar
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Wax - an amorphous solid
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B. Liquids
(Molecular Motion)

• No definite shape but a definite volume - takes
  on the shape of its container.
• Particles not held as closely together - free to
  move - flow.

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- 100 mL of water 100 mL in any shaped
container. (Definite volume)
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• Liquids do not easily compress or expand.
• Viscosity - (a property of liquids) is the
  resistance of a liquid to flow
• - honey has a high viscosity compared to water

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Is lava liquid? Is it viscous?
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C. Gases

• Have no definite shape or volume - volume can
  change.
• Will fill any available space - a small amount of
  gas can fill a large volume.
• Will expand without limit.

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-Gases can be compressed. A larger amount
forced into a smaller space. (A change of
volume)
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The tanks worn by this diver contain several
hours of air. How does this work?
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(Molecular Motion)
Molecules of a gas are free to move. They move
very rapidly and are in constant motion.
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This is the Eagle Nebula. Its gas dust are
expanding in space.
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What would happen if this balloon had a hole in
it? What limits the gas?
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D. Plasma

• 1. Plasma is - a super-heated, electrically
  charged gas.
• Plasma is rare on earth.
• Plasma is extremely energetic dangerous.

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Examples of plasma - the sun
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Light bulbs Neon lights
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Lightning
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Remember - particles of matter always move.
(Molecular Motion)

• Solids - particles vibrate in place, tightly
  bound together
• Liquids - particles are freer, move faster - flow
• Gases - particles even more free, rapid movement
• Plasma - very rapid movement, lots of energy

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Temperature affects particle movement. Heat -
move faster. Cold - move slower.

• Absolute zero-
• the temp. at which all molecular motion ceases.
• - 273o C
• 0o Kelvin
• - 459o F

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This is dry ice (CO2). What happens to it as
the temperature rises? What are its molecules
doing?
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This is water ice (H2O). What happens to it as
the temperature rises? What are its molecules
doing?
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II. Gas Behavior

• A. Measuring Gases
• 1. - volume can change - gas will fill any
  available space so will be the same volume as
  its container
• 2. - temperature is the average energy of motion
  of the particles of a substance

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(3. Temperature)
- The faster the particles are moving, the
greater their energy and the higher the
temperature - A thermometer - a speedometer for
molecules! - Gas molecules at 20o C - travel
at 500 meters per second (typically)
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4. Pressure

• Gas particles - constantly move collide with
  each other the walls of their containers.

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(4. Pressure)

• This results in an outward push by the gas.
• This outward force is called pressure.
• Pressure Force/Area
• Measured in units of kilopascals(kPa)

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Objects like a soccer ball or balloon, have gas
under pressure inside that keeps them inflated .
This is a pressurized space suit. - What happens
if any of these get a hole in them?
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4. Relating Pressure Volume

• Gases behave in predicable ways.
• Robert Boyle - English scientist in the 1600s
• - found that when the pressure of a gas is
  increased at a constant temperature, the volume
  of the gas decreases. When the pressure
  decreases, the volume increases.

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BOYLES LAW
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• Boyles Law also applies to situations where
  volume of a gas changes.
• Then the pressure also changes.

What would happen to the pressure the volume
if you squeezed one of these balloons in your
hands?
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5. Relating Pressure Temperature

• Thought Exercise
• Think of a sand storm.
• Would pouring a handful of sand over your arm
  feel different than being in a strong storm?
• HOW?

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The greater the speed of the sand particles, the
more energy they carry transfer.

• Gas particles also travel at great speeds.
• Remember pressure measures how much gas
  particles push outward on their container.
• - the greater the speed of the gas
  particles, the greater the pressure.
• - Temp. is the average speed of particles.

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Charless Law - 1700s French Scientist Jacques
Charles

• When the temperature of a gas at a constant
  volume is increased, the pressure of the gas
  increases.
• When the temperature is decreased, the pressure
  of the gas decreases.

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Charless Law
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III. Graphing Gas Behavior

• Graphs are diagrams that tell how 2 variables or
  factors are related.
• - graphs can be used to make predictions

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Collecting data - use a data table
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Data from a data table can then be graphed.
This graph shows the linear relationship between
temp. volume which are directly proportional.
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This graph shows the relation- ship between
pressure volume which varies inversely.
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IV. Changes of State - physical change of matter
from one state or phase to another. (ex. solid -
liquid)

• A. Energy changes in state
• 1. A substance changes state when its thermal
  (heat) energy increases or decreases by a
  sufficient amount.
• 2. Thermal energy - the energy of a
  substances particles
• - transferred from one substance to another

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- always flows from a warmer substance to a
cooler substance

• Remember the arrangement motion of particles
  in a substance determine whether substances are
  solid, liquid, or gas.
• - particles of solids have the least thermal
  energy, gas the most.

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B. Changes of State or Phase

• 1. MELTING - solid to liquid
• - melting point of a substance is determined
  by how strongly its particles are attracted.
• - Thermal energy makes molecules vibrate
  faster. At a certain temperature (the melting
  point) they can break free.

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Melting wax
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Melting ice - ice begins to melt at 0o C, the
temperature at which molecules are moving fast
enough to flow as a liquid.
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Molten silver - What happens to the molecules as
the metal cools?
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Do substances require the same amount of thermal
(heat) energy to melt? THINK of melting - water
ice - steel - plastic - rock
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2. Freezing - liquid to solid

• Liquid loses energy as it cools.
• Molecules slow down.
• When water reaches 0oC, its molecules are moving
  so slowly that it starts to form into regular
  patterns - ice crystals
• This is the same temperature at which ice melts!

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So what does happen to molten silver
molecules as the metal cools?
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3. Vaporization - liquid to gas

• Occurs when a liquid gains enough energy to
  become a gas.
• Two main types
• - evaporation - molecules on the surface
  escape
• - ex.s a drying puddle, sweating
• - boiling -takes place inside a
• liquid on the surface

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Note Evaporation happens at the surface
boiling inside the liquid. Boiling is actually
water molecules turning into a bubble of gas
inside the liquid then bubbling out as
densities change. Which requires more energy?
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- a. boiling point - is the
temperature a which a liquid boils

• Boiling points of substances
• - water (at sea level) 100oC
• - salt 1413o
• - diamond 4827oC
• Boiling point is affected by air pressure. The
  lower the air pressure, the less energy is needed
  for molecules to escape. Water will boil at 95oC
  in Denver, Colorado.

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4. Condensation - gas to liquid

• Occurs when gas particles lose enough energy to
  become a liquid.
• - ex.s clouds, mist,breath on a mirror
• Steam is NOT condensation (water vapor) but tiny
  drops of liquid water suspended in the air.

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Water vapor condensing on a flower. This
happens when the water vapor touches a cooler
surface loses thermal energy. Think of a cold
glass on a humid day.
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Fog - water vapor cooling condensing in the
rainforest.
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5. Sublimation - solid to gas

• Occurs when the surface particles of a solid gain
  enough energy to become a gas.
• - particles do NOT pass through a liquid
  state.
• Ex.s - dry ice, naphthalene(moth balls,) iodine,
  water ice

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Dry ice - CO2 Note that the fog you see is not
CO2 gas, (you cant see that) - its water vapor
condensing in the cold surrounding the dry ice.
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Dry ice - CO2
Sublimating - Iodine
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Water ice snow will also sublimate. How could
this happen? Hint It happens in very cold
places like Antarctica.
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C. Identifying Substances Through Changes of
States/Phase

• The properties of substances can help to identify
  them.
• - boiling/melting points
• If you were given 3 colorless liquids you could
  identify them by their boiling melting points.

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• Freezing - Boiling
• Water 0o - 100o C
• Ethanol -117o - 79o
• Chloroform - 64o - 61o