states of matter chapter 13. pretest on prior knowledge cw credit not for a grade, just to see what...

States of Matter

Chapter 13

Pretest on prior knowledge

• CW credit

• Not for a grade, just to see what you already know

• Good Luck!

States of Matter

ESSENTIAL QUESTIONS• Compared to solids and

liquids, what is unique about gases?

• How do substances change from one state to another?

OBJECTIVES• Recall properties on states

of matter• Explain why gases are easier

to compress than solids or liquids

• Analyze and interpret a phase diagram

Chemcatalyst: __.__

• Name some properties of solids:

• Can you give some examples of solids?

Solids

• Particles have fixed locations

• Packed tightly together in an orderly arrangement

• Vibrate in place

Properties of solids

• Not easily compressible

• Do not FLOW because they are packed tightly

• No effect with an increase of pressure

Think back…

• Which type of compounds are only solids at room temperature??

IONIC COMPOUNDS

Crystal Structure

• Orderly arranged particles in a pattern

• Also, known as a lattice

• A unit cell is the smallest part of a crystal that retains its shape

Allotrope

• A substance that exist in more than one form

• Carbon has 3 allotropes

• Graphite (in pencils)

• Diamonds (thanks Mr. Herman)

• Buckministerfullerene (C60)

Other Allotropes

OxygenO2 or O3

PhosphorusRed or white

Amorphous solids• A solid that lacks order

within its internal structure

• These solids are randomly arranged

• Example: Glass, plastic, synthetic fibers, rubber

Crystal Lattice or Amorphous SolidA B

Nanotechnology

• Nanotechnology and solar cells

Chemcatalyst :__.__

• Why do you add salt to a pot of water?

Liquids

• Particles are spaced out more than solids

• Particles feel attraction between each other which keeps them close

• Less dense than solids

Properties of Liquids

• Take the shape of the container

• Definite volume

• Ability to flow (fluid)

• No effect with an increase of pressure

What’s a fluid?

• A continuous substance whose molecules move freely past one another and that has the tendency to assume the shape of its container

Boiling Point

• A liquid is heated to a temperature where the particles have enough kinetic energy to vaporize

• The liquid begins to bubble because the vapor is rising and escaping the container

Boiling Point (BP)

• At a particular temperature the vapor pressure is equal to the external pressure

• During the boiling process the temperature is constant

• Since, its based on pressure, not all liquids will boil at the same temperature

BP & Pressure

• Altitude will affect boiling points

• As you go up to higher altitudes, the pressure is lower; which in turn would lower the boiling point.

Think about this…

Would the temperature at which water boils be higher or lower than 100oC?

•Denver is 1600 m above sea level

Water actually boils at 95oC!!!

Kinetic energy and states of matter

• If Kinetic energy increases all particles begin to move faster and in turn change phase

• Kinetic energy is directly proportional to temperature

Why do you add salt to a pot of water?

By adding salt to your pot, it raises the BP to 102oC, but salt water has a lower heat capacity than typical water.

Needs less energy to heat the water

What would be a more effective way to boil water, than salt?

Think about pressure

Small scale Lab

• The behavior of liquids and solids

Chemcatalyst __. __

• Explain the differences between a NaCl crystal compared to a piece of glass.

• What happens to kinetic energy when temperature decreases?

• If the pressure is lower, does boiling point change?

Gases

• Small, hard particles

• Empty space in between

• Particles are far apart

Gases• Insignificant volume and no shape

• No attractive or repulsive forces between particles

• Move in straight lines until a collision

• Elastic collisions

• Flows like a fluid

Is a gas a fluid?

• Gases have the ability to flow because they can move past one another

• What happens over time as Bromine gas is left in the beaker?

Is there a difference between a gas and a vapor?

• At room temperature, a gas is a gas– Example: Chlorine gas (Cl2), oxygen gas (O2)

• At room temperature, a vapor is in some other form– Example: Water Vapor (H2O)

Gas Pressure

• Results from the force exerted by the gas on an object

What is causing this force?

• The particles colliding with themselves and the object

• The force applied is very small for one, but imagine millions!!

Gas Pressure & a Vacuum

• A vacuum is where there are no particles, thus no pressure

• Space is a vacuum!

Think about this…

• Why can no one hear you scream in space?

• It’s a vacuum and sound needs a medium to travel

Measuring Pressure

Barometer•Used to measure atmospheric pressure•Air pressure decreases as altitude increases

Chemcatalyst __.__

A. SolidB. LiquidC. Gas

1. Ability to flow and has a definite volume

2. An ordered pattern with particles in fixed positions

3. Particles have elastic collisions4. Particles feel attraction between

each other5. Particles vibrate in place6. Move in straight lines, until a

collision

Match the Property with the correct state of matter:

B

A

C

A or B

A

C

Changes of State

• A physical change occurs as a substance undergoes a change from solidliquidgas

• Energy is needed to complete this change

Solid Liquid

• Melting• Particles within a solid gain enough energy to

move into the liquid phase

• The organization of the particles break down

• Melting point (MP) the temperature at which it goes from solid liquid

Liquid Solid

• Freezing

• Lowers the energy or temperature where particles become more rigid in its shape

• Freezing Point (FP)- the temperature where a liquid begins to freeze

Did you know?!

• The melting point and the freezing point is the same EXACT temperature!!!

• Meaning solid and liquid are at equilibrium, until it shifts towards either one

Think back…

• Which one has a higher melting point?

Salt or Sugar?(NaCl or C12H22O11 )

Salt is an ionic compound, while sugar has weaker covalent bonds

Liquid Gas

• Evaporation• Also, known as vaporization

• When liquid particles gain enough energy to leave the liquid phase and escape as a gas

• Since, the most energetic particles are leaving the leftover temperature decreases

Did you know?!

• Evaporation is a cooling process

• By sweating, your sweat is evaporated and in turn cooling down your body

Gas Liquid

• Condensation

• A loss of energy returns the gas to the liquid phase

Solid Gas

• Sublimation

• A solid skips the liquid phase and becomes a gas

• Occurs when the solid has a vapor pressure that is greater than atmosphericpressure at or near room temperature.

But doesn’t sub mean below?

• Sublimation is from the Latin word sublimare, which means to raise or elevate!!

Gas Solid

• Deposition

• Gas/vapor becomes a solid and skips the liquid phase

• Used for making computer chips and purifying mixtures!

Let’s make this concept map

Solid

LiquidGas

MeltingFreezing

Condensation

Evaporation

Sublim

ation

Depositi

on

Answer the following in complete sentences:

• Is a phase change a chemical or physical change and explain why.

Chemcatalyst: __.__

• Which change of state occurs when liquid becomes solid?

• Is there an increase or decrease of temperature/kinetic energy for this change?

• What happens to the particles during this change?

Phase Diagram

• A phase diagram shows the relationship between the 3 states

• Shows conditions (temperature & pressure) at which phases are at equilibrium

Phase diagram

• Let’s shade the 3 phases of our diagram

Phase Diagram

• Triple Point- where all 3 states exist at once• Critical Point- no phase boundaries exist

Phase Diagram

• Each line represents an equilibrium between changes of states

Phase Diagram

• Normal means at standard pressure

Or MP

Phase diagram Practice

• What temperature and pressure is the triple point?

• What temperature and pressure is the critical point?

• What temperature and pressure of the normal MP and BP?

Phase diagram PracticeA. Pressure

B. Temperature

C. Triple point

D. solid

E. Liquid

F. Gas/Vapor

G. Critical Point

H. Normal FP/MP

I. Normal BP

Chemcatalyst __.__

A B

G H

F

C

Describe what’s happening:

Label and answer the following:

1. What state of matter would be at 75.0 Kpa and -120oC?

2. What is the normal boiling point for Xe?