In This Lesson:
Unit 5
States of Matter
(Lesson 1 of 3)
Today is Wednesday,
May 7th, 2014
Pre-Class:
What are the three (or four…or five)
states of matter?
What do you call the transitions
between the phases?
Please take a scavenger hunt and
vocabulary list. You will also need a
paper towel.
Stuff You Need:
Calculator
Paper Towel
Today’s Agenda
• Chapter 13
– No, really. We’re doing it all today. It’s just
vocabulary and concepts.
• Why cooking takes longer at higher altitudes.
• Where is this in my book?
– Uh, Chapter 13?
– P. 385 and following…
By the end of this lesson…
• You should be able to identify various
properties and concepts relating to the three
most common phases of matter.
• You should be able to convert between
pressure and temperature units.
Phases of Matter
• There are four main phases of matter:
• Solids
– Ice
• Liquids
– Water
• Gases
– Water Vapor
• Plasma [Term 12]
– Plasma is similar to a gas and consists of ions at
extremely high temperature. The surface of the sun is
plasma.
http://en.wikipedia.org/wiki/File:Plasma-lamp_2.jpg
Phases of Matter
• There are also Bose-Einstein Condensations.
They’re even weirder.
– Instead of being hot, they’re extremely cool.
– All the atoms condense into a single, well, blob.
– Weird.
Phase Transitions
• Going from a solid to a liquid is:
– Melting (also called fusion)
• Going from a liquid to a solid is:
– Freezing (also called solidification)
• Going from a liquid to a gas is:
– Boiling (or evaporation/vaporization)
• Going from a gas to a liquid is:
– Condensing
• Going from a solid to a gas is:
– Sublimation [Term 14]
• Going from a gas to a solid is:
– Deposition
Phase Changes
Sublimation
Melting
(fusion)
Boiling
(evaporation or
vaporization)
Freezing
(solidification)
Condensation
Deposition
Sublimation Demo
• To the fume hood!
• Let’s watch as iodine crystals (solid) sublime
into iodine gas.
– Note: Iodine gas (and iodine itself) is TOXIC.
• Another example of sublimation is dry ice.
• Still another example, in case you don’t think
you’ve seen much sublimation in your life, is
when snow and ice disappear from the ground
despite the temperature being below freezing.
Phases of Matter
• We learned a long time ago that all matter has
mass and anything with mass is probably
matter.
• What about a location in which there is no
matter? What’s that called?
• It’s a vacuum [Term 16]. No matter. Not even
gas. Nothin’.
– Like outer space!
Kinetic Theory
• Kinetic energy [Term 10] is the energy of motion.
– If you’re running, you’ve got a lot of motion.
• Kinetic theory [Term 11] states that all particles are
in motion at all times, unless they’re at 0 K (-273 °C
or -459.67 °F) – absolute zero.
• Absolute zero has never been achieved, even in a
lab.
– Still, we’re pretty sure that if something were to reach 0 K,
everything would stop.
– Closest achieved? 0.0000000001 K, or 100 picokelvins
(pK).
• Okay technically there’s a way to get below 0, but…yeah.
Kinetic Energy and Temperature
• Temperature is a measure of the average kinetic
energy of a substance’s particles.
• The Kelvin temperature scale is used because it is
proportional to the average kinetic energy of
particles of a substance.
– Helium atoms at 200 K have twice the energy of
Helium atoms at 100 K.
•
•
•
•
How to calculate Kelvin?
°C + 273 = K
°C = K – 273
Fun Fact: Technically, °C = K – 273.15…
Gas Pressure
• Gas Pressure [Term 5] results from atoms or
molecules in a container colliding with each
other and the sides of the container.
• Atmospheric pressure [Term 1] is pressure
from air molecules colliding with objects.
– At sea level, we’re all under 14.7 lbs of air
pressure!
Aside: Gas Pressure
• So how often do gas molecules collide?
• Down here at roughly sea level, a gas
molecule moves an average of 3 millionths of
an inch before it collides with another one.
• At the edges of the atmosphere, there may
only be one or two molecules every few miles.
Measuring Atmospheric Pressure
• A barometer [Term 2] is
used to measure
atmospheric pressure.
• Air pushes down on mercury
which rises up a glass tube
proportionate to the
pressure of the air.
Barometer
Atmospheric Pressure
• Is air pressure higher or lower at high altitudes?
• Consider this:
Edge of Earth’s Atmosphere
Force of Air
Force of Air
Lower Pressure
Standard Atmosphere
• A Standard Atmosphere [Term 13] (or standard
atmospheric pressure) is like “room temperature”
except for pressure.
• Standard pressure is:
–
–
–
–
1 atmosphere (atm)
760 mm Hg
760 torr (named after discoverer of barometrics)
101.3 kPa (kilopascals) – pascal (Term 10) is the SI unit
of pressure
• MEMORIZE THESE!
Standard Temperature
• Standard temperature for gases is 0 °C or 273
K.
• Therefore, Standard Temperature and
Pressure (STP) is the combination of the two.
Pressure Unit Conversions
• Express 100.0 kPa in torr.
starting measurement target unit
given unit
100.0 kPa
760 torr
= 750.2 torr
101.3 kPa
• 100 kPa = 750.2 torr
Pressure Unit Conversions
• 2 atm = ? torr = ? mm Hg = ? kPa
– 1520 torr, 1520 mm Hg, 202.6 kPa
• 1.7 atm = ? torr = ? mm Hg = ? kPa
– 1292 torr, 1292 mm Hg, 172.21 kPa
• ? atm = ? torr = 800 mm Hg = ? kPa
– 1.05 atm, 800 torr, 106.63 kPa
• ? atm = ? torr = ? mm Hg = 81 kPa
– 0.80 atm, 608 torr, 608 mm Hg
Vaporization or Evaporation?
• There’s a difference. Thoughts?
• What if I told you it has to do with the
temperature at which the process is occurring?
• Vaporization [Term 18] is when a liquid goes to a
gas.
– Particles at the surface gain enough kinetic energy to
break free from the liquid and become a gas.
• Evaporation [Term 4] is when a liquid goes to a
gas when the liquid is not boiling.
Boiling Point
• Vapor pressure [Term 17] is the force of
evaporated liquids in a sealed container.
– Liquid evaporates to gas, gas pushes on the
container and liquid.
• Boiling point [Term 3] is the temperature at
which the vapor pressure equals the
atmospheric pressure.
– Causing bubbles to form as the liquid boils.
Boiling Point
• Normal boiling point [Term 9] is the boiling point
of a liquid at standard pressure (101.3 kPa).
• In Doylestown, at standard pressure, water boils
at 100 °C.
• In Denver, at lower pressure (higher altitude so
less air above), water boils at 95 °C.
– So cakes take longer to bake because temperature
must be kept lower.
– This is also how pressure cookers work, in a way.
Low Boiling Points
• Nitrogen is most commonly found as a gas,
but that’s only because it’s got a VERY low
boiling point.
• Nitrogen boils at -196 °C.
• Below that temperature, it’s a liquid – liquid
nitrogen.
• Video!
Melting Point
• Melting point [Term 8] is the temperature at
which a solid becomes a liquid.
• Once again, a friendly reminder that melting is
also called fusion.
Phase Diagram
• Phase diagrams [Term 11] show the
relationship between pressure, temperature,
and the three phases of matter for a chemical.
• The triple point [Term 15] is the point at
which all three phases can exist at the same
time.
• Video: Water Boils and Freezes at the Same
Time
Phase Diagram of Water
Heating/Cooling Curve
• Similarly, a heating/cooling curve shows the
temperature and energy of a substance over
time as it goes through phase changes.
Closure
• In addition to the notes you took today, I will
be posting this PowerPoint and a “key” to the
vocabulary sheet.
• It’s not all necessary to know, but it may help
you understand terms you didn’t in class.
• My Website > Chemistry > Worksheets and
Keys.