Transcript Physical Science

Physical Science
Chapter 16: Solids, Liquids, and
Gases
Kinetic Theory of Matter
(explanation of how particles in matter behave)
• All matter is composed of small particles
(atoms)
• Particles are in constant, random motion.
– Absolute zero: temperature at which all motion
would stop, if it could be reached
• 0K, -273 C, -459 F
• These particles are colliding with each other
and the walls of their container. These
collisions are perfectly elastic.
• Think of it like a snowball. The more tightly
you pack it, the more strongly the flakes
(particles) are bonded together. Pack it
loosely, and the flakes are more likely to fly
apart (loosely bonded).
• Also, particles vibrate more or move around
more quickly if the matter is heated up.
Conversely they also slow down as they are
cooled.
• Adding and removing heat is the #1 way to
change a material from 1 state of matter to
another. (we’ll talk about this later)
There are 4 different states of
matter:
•
•
•
•
A.
B.
C.
D.
Solid
Liquid
Gas
Plasma
• What is the relationship between the
temperature of the particles and their rate of
movement or vibration?
Solids
• Have a definite shape
and a definite volume
• Particles are tightly
packed and are
bonded together
relatively strongly
• Diamonds form under tremendous pressure,
and therefore their particles (carbon atoms)
are packed very tightly. This is one reason
why diamonds are so hard.
Crystalline and Amorphous Solids
• The particles of many solids are arranged in
definite repeating patterns. These are called
crystalline solids.
• Gemstones, minerals like salt, and safety
glass are all examples of crystalline solids.
They have a predictable pattern of particles.
• Amorphous solids have no definite
structure or arrangement of their particles.
• These materials will break in an
unpredictable manner, with no pattern.
• Examples include plastics, glass, and wax.
Liquids
• Have a definite volume, but no definite shape
(they take the shape of their container)
• Particles move around freely within the liquid.
Viscosity in fluids
• Viscosity is the property of a fluid which
describes how well it will flow
• Low viscosity flows easily, high viscosity is
much thicker.
Gases
• Gases have no definite
volume and no definite
shape (but do have mass).
They simply take the
shape of the container
they are in.
• Gas particles are very
loosely bonded and move
around freely.
• Gases, unlike solids and liquids, are fairly
easy to compress and also readily expand.
That is why we say they have no definite
volume.
• Expansion and contraction of gases explains
why warm air rises and cold air sinks.
• Why does it hurt more to jump onto a
water bed than on an air mattress?
• Plasma, the 4th state of matter, is the most
common state of matter in the universe. It is a
gas-like mixture of positive and negatively charged
particles.
These particles make plasma a high energy state
of matter.
• A plasma TV has a large number of tiny cells
containing xenon and neon gases. When an
electric current is passed through these individual
cells, they give off energy which causes phosphors
inside the cell to give off light. These tiny lights
combine together to produce an image.
Changes of state
• By adding or
removing thermal
energy from a sample
of matter, it is often
possible to cause it to
change from one
state of matter to
another.
Melting and Freezing
• Adding thermal energy
can change some
materials from a solid to
a liquid (melting)
• Removing thermal
energy may change
some materials from a
liquid to a solid (freezing)
• Let's say an ice storm knocks out your
power so you light some candles.
As the melted wax drips off, it solidifies as
it cools. Is this considered freezing?
Condensation & Evaporation
• Changing a gas to a liquid
is called condensation
(loses heat)
• Ex.: breathing on a cold
window, warm air rising and
forming clouds, droplets on a
cold glass, dew
• Evaporation is where a liquid changes to a
gas (gains heat).
• Ex.: steam rising from a hot liquid, sweat
cooling your body, a steam locomotive
• Is boiling the same as evaporation?
• How do the bubbles magically appear
in a pot of boiling water?
NO!
• Evaporation happens only at the surface
of a liquid and occurs at any temperature
• Boiling happens throughout the bulk of a
liquid, rising in a bubble to the surface. It
only happens when the temperature is
above the boiling point of that substance.
• When a substance boils and matter is
transformed from a liquid to a gas, this is
called vaporization.
Sublimation
• Changing a solid directly to a gas is called
sublimation.
• Examples: dry ice, frost on a window
Deposition
•Changing a gas
directly into a solid
•Ex: snow and frost
• This is why you don’t make dry ice bombs!
Phase Changes
• Changing from one state of matter to
another.
• Amount of heat in the substance
determines the phase of matter it is in.
• Substances can be made to change
phases by adding or removing heat
3 Phase Changes
• Solid to Liquid
– Melting point if
adding heat
– Freezing point if
removing heat
• Solid to Gas
– Sublimation if
adding heat
– Deposition if
removing heat
• Liquid to Gas
– Boiling point if
adding heat
• Vaporization if adding
heat
• Evaporation at the
surface of the liquid
– Condensation if
removing heat
Behavior of Gases
Pressure:
the amount of force exerted by
the gas per unit of area
Pascal: (Pa) SI unit of pressure
1 Pascal = 1000 kPa (kilopascals)
Atmospheric pressure at sea level is 101.3 kPa
Pressure, Temperature and Volume
“PTV card”
If volume increase, pressure decreases.
If volume decrease, pressure increases.