Today is Thursday, May 7 th, 2015 Pre-Class: What are the three (or four…or five) states of matter? What do you call the transitions between the phases?

Today is Thursday,May 7th, 2015

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 small

paper towel.

Stuff You Need:Calculator

Paper Towel

In This Lesson:Unit 5

States of Matter(Lesson 1 of 3)

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 16]– 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 18]

• Going from a gas to a solid is:– Deposition

(evaporation or vaporization)

Phase Changes

Sublimation

Deposition

Melting(fusion)

Freezing

Boiling

Condensation(solidification)

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 21]. 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.

Nature of States

• Gases:– No definite volume or shape– Low attraction between molecules– High ability for molecules to move– Pressure highly affects volume

• Liquids:– Definite volume, no definite shape– Medium attraction between molecules– Medium ability for molecules to move– Pressure has little effect on volume

Nature of States

• Solids:– Definite volume and shape– High attraction between molecules– Low ability for molecules to move• They tend to vibrate in place

– Pressure has little effect on volume

The Nature of Gases

• Kinetic Theory states that:– Gas is composed of atoms/molecules.– Gas particles are in constant and random rapid

motion.– All collisions are perfectly elastic.• When they collide, the energy from one is transferred

completely to the other.• Total kinetic energy remains constant, something we’d

expect from the Law of Conservation of Energy.

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 8] results from atoms or molecules in a container colliding with each other and the sides of the container.

• Atmospheric pressure [Term 3] 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 4] 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 17] (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 14) 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.

• 100 kPa = 750.2 torr

starting measurement target unitgiven unit

100.0 kPa torrkPa

= 750.2 torr760

101.3

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 23] 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 7] is when a liquid goes to a

gas when the liquid is not boiling.

Boiling Point

• Vapor pressure [Term 22] is the force of evaporation of liquids in a sealed container.– Liquid evaporates to gas, gas pushes on the

container and liquid.• Boiling point [Term 5] 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 13] 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 (-320.8 °F).• Below that temperature, it’s a liquid – liquid

nitrogen.• Video!

Melting Point

• Melting point [Term 12] is the temperature at which a solid becomes a liquid.

• Once again, a friendly reminder that melting is also called fusion.

Types of Solids

• Crystalline solids [Term 6] (or crystals) have molecules arranged in an orderly pattern.– The smallest group of particles within a crystal

that keeps the shape of the crystal is called a unit cell [Term 20].

Sim

ple

Cubi

cU

nit C

ell

Body

-Cen

tere

d Cu

bic

Uni

t Cel

l

Face

-Cen

tere

d Cu

bic

Uni

t Cel

l

Types of Solids

• Amorphous solids [Term 2] are solids whose molecules have no ordered structure.– Example: Glass [Term 9].

• Allotropes [Term 1] are two or more molecular forms of the same element in the same physical state.– Example: Carbon (as graphite or diamond)

Phase Diagram

• Phase diagrams [Term 15] show the relationship between pressure, temperature, and the three phases of matter for a chemical.

• The triple point [Term 19] 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.