Agenda:

Thermochemistry Heating & Cooling Curves – a review Graphing temperature change Phase Change Diagrams Review: Energy in Chemical

Reactions Intermolecular Forces

Impact of polarity, shape and sizeVSEPR - shape

Homework: New Element Project

Warm-up:

Atomic size is one of the many trends of the Periodic Table.

- Describe one reason atomic size many vary between the elements on the Periodic Table.

- Arrange these elements in descending order: Al, Mg, P, Si, Na, S

- Explain why you chose this order.

Characteristics of Solids, Liquids & Gases

Sort the terms into 3 columns: S, L, G(Hint: Look for 3 cards with similar wording

and determine which best fits solid, liquid or gas)

Solid Liquid Gas

Most substances, like water, can exist in all three states.

A cloud is made of water vapor, a type of gas.

An iceberg is made of water in solid form.

This glass contains liquid water.

WHAT ARE THE CHANGES OF STATE?

GAS

SOLID LIQUID

Deposition

Sublimatio

n

Boiling / Evaporation

Condensation

Freezing

Melting

Which are endothermic?

Which are exothermic?

Changing States (Phase changes)

SolidGas

Liquid

Increase Thermal Energy (Heat up)

Decrease Thermal Energy (Cool off)

Where on the picture would we place: - Melting Point?- Boiling Point? - Condensing Point?- Freezing Point?

States of matter, energy & phase changes

Energy levelEnergy changePhase changesMP/BP

Entropy= degree of disorder

Melting point

Melting - change from solid to liquid Melting point - SPECIFIC temperature when

melting occurs. Each pure substance has a SPECIFIC melting

point.Examples:M.P. of Water = 0°C (32°F) M.P. of Nitrogen = -209.9 °C (-345.81998 °F)M.P. of Silver = 961.93 °C (1763.474 °F) M.P. of Carbon = 3500.0 °C (6332.0 °F)

Melting Point

Particles of a solid vibrate so fast that they break free from their fixed positions.

Solid Liquid

Increasing Thermal Energy

Melting point

Vaporization

Vaporization – change from liquid to gas Vaporization happens when particles in a

liquid gain enough energy to form a gas.

GasLiquid

Increasing Thermal Energy

Boiling point

Two Kinds of Vaporization

Evaporation – vaporization that takes place only on the surface of the liquid

Boiling – when a liquid changes to a gas BELOW its surface as well as above.

Boiling Point

Boiling Point – temperature at which a liquid boils

Each pure substance has a SPECIFIC boiling point.Examples:B.P. of Water = 100°C (212°F) B.P. of Nitrogen = -195.79 °C (-320.42 °F)B.P. of Silver = 2162 °C (3924 °F) B.P. of Carbon = 4027 °C (7281 °F)

States of matter, energy & phase changes

Energy levelEnergy changePhase changesMP/BP

Entropy= degree of disorder

Heating and Cooling Curves of a Substance Representing MP, BP, CP, FP

Heating Cooling

Energy (heat) added Energy (heat) released:

Intermolecular Forces

Forces between molecules (compounds) which helps determine whether a substance is a solid or liquid

Gases have little/no intermolecular forces

Energy requirements for water Three formulas : specific heat Q = mCp∆T

heat of fusion Q= mHf

heat of vaporization Q= mHv

Heating Cooling

Energy (heat) added Energy (heat) released:

Energy calculations related heating or cooling specific substances

Specific heat (Cp)

Latent heat Heat of fusion (Hf) Heat of vaporization (Hv)

Use reference tables – values for each pure substance

Heat calculations – 3 formulas

Specific heat = heat required to raise the temperature of 1 gram of substance 1 °C

Formula: Q = mCp∆T Specific heat

Specific for each pure substance Use reference tables

Heat calculations – 3 formulas

Heat of fusion - Amount of heat added to melt a substanceAmount of heat released to freeze a

substance

Formula Q= mHf

Specific for each pure substance Use reference tables

Heat calculations – 3 formulas

Heat of vaporization- Amount of heat added to boil a substanceAmount of heat released to condense a

substance

Formula Q= mHv

Specific for each pure substance Use reference tables

Heat energy In a heat calculation

problem, if the problem asks about melting/freezing you would multiply the mass times _____________________. heat of fusion heat of vaporization or specific heat

In a heat calculation problem, if the problem asks about vaporizing/condensing of steam, you would multiply the mass times ________. Heat of fusion Heat of vaporization Specific heat

In a heat calculation problem, if the problem asks about a change in temperature, you would multiply the mass times ___________________ times the change in

temperature. Heat of fusion Heat of vaporization Specific heat

 

Thermochemistry Problems related to water

1. How much heat is required to raise the temperature of 789 g of water from 25oC to 70oC?

 

2. How much heat is released when 432 g of water cools from 71oC to 18oC?

 3. How many joules of heat are given off when 5.9 g of

steam cools from 175oC to 125oC? 

4. How many joules does it take to melt 35 g of ice at 0oC?

5. How much heat is released when 85 g of steam condense to liquid water?

  6. How much heat is necessary to raise the temperature

of 25 g of water from 10 oC to 60 oC?

  7. How much heat is given off when 50 g of water at 0oC

freezes?

 

How much energy is needed to heat water from a solid to a vapor?

Graph the data – using most of the graph paper

Time (when heat energy is added) Resulting temperature

See Textbook

Review: Heating curve with heat formulas

Scroll down http://www.kentchemistry.com/links/Matter/

HeatingCurve.htm

What factors impact change?

Intermolecular forces

Energy

Conditions: T, P, V, amount,

Phase Diagrams: What is added to this diagram? Why?

Phase diagrams

http://www.youtube.com/watch?v=fLOPaJ8lcr8&feature=endscreen&NR=1

T °C 200 °C -2°C 100 °C -2 °C 30°C 100 °C

P - atm 1 atm 1 atm 100 atm 0.001 atm 0.8 atm 1 atm

Phase Liquid Vapor

For Water

A = B= C= D=

PHET States of Matter http://phet.colorado.edu/en/simulation/stat

es-of-matter

Phase Diagrams. Use the phase diagram for water below to answer the following questions.

What is the state of water at 2 atm and 50- C?

What phase change will occur if the temperature is lowered from 80-C to -5-C at 1 atm?

You have ice at -10-C and 1 atm. What could you do in order cause the ice to sublime?

Review: Interpreting Phase Diagrams

Interpreting a Phase Diagramof Water at varying pressuresExample: 100 atm

 

1) What is the normal melting point of this substance? ________

 

3) What is the normal boiling point of this substance? ________

 

4) What is the normal freezing point of this substance? ________

 

5) If I had a quantity of this substance at a pressure of 1.25 atm and a temperature of 00 C and heated it until the temperature was 7500 C, what phase transition(s) would occur? At what pressure(s) would they occur?

 

 

 

6) At what temperature do the gas and liquid phases become indistinguishable from each other? ________

7) If I had a quantity of this substance at a pressure of 0.25 atm and a temperature of -1000 C, what phase change(s) would occur if I increased the pressure to 1.00 atm? At what temperature(s) would they occur?

Water: Connecting Phase Diagram and Heating Curve

Vapor Pressure – Physical Equilibrium

The vapor pressure is the pressure measured when there is an equilibrium between the gas and liquid phases. The rates of condensation and vaporization

are equal.

Vapor pressure

http://www.chem.purdue.edu/gchelp/liquids/vpress.html

Discovery Ed video

Resources for S, L, G

http://www.kentchemistry.com/links/Matter/HeatingCurve.htm

http://www.middleschoolchemistry.com/

How does the chemical composition of a substance impact whether it is a gas, liquid or solid at room temperature?

Overview: Factors that Impact State of Matter

1. Type of compound – Ionic, Covalent, Metallic

2. Intermolecular Forces, impacted by 1. Shape

2. Size

3. Polarity

Intermolecular Forces Attractive forces between molecules

Not between individual atoms

Much weaker than the bonds within a molecule Intramolecular bonds form between 2

atoms in a molecule/compound_________ , _________, ________

Can determine the state of matter by the number and type of these forces Lots of forces= liquid Lots and lots = solid

What causes these intermolecular forces? Opposites attract:

In chemistry this means:

How do these attraction between molecules form? Polarity (partial polarity) Shape Size

Intermolecular Forces

Three Types Hydrogen Dipole – dipoleLondon Dispersion (Van der Waals)

Based on weak attraction between molecules partial negative – partial positive

Let us review – covalent bondsIntramolecular bond

Type of atoms in covalent bond Electronegativity Difference

Sharing valence electrons to form bondsSome share equally = non-polar covalent

bondsSome share unequally = polar covalent bonds

Electronegativity Differences Electronegativity Differences = ∆EN

∆ O ∆ 3.2

Ionic BondsCovalent bonds

∆ 1.7

Increasing polar (+ side and – side) characteristics

Review

Review

Electronegativity Difference

The electronegativity difference must be equal to or less than _______.

It is a polar covalent bond if the difference is between __________.

It is a non-polar covalent bond if the difference is between ___________.

Review

Non-Polar Covalent Bond ∆EN= 0 – 0.3

The Electron pair that makes up the bond is shared evenly.

Review

Non-Polar Covalent BondReview

Polar Covalent BondReview

Polar Covalent BondReview

Polar Covalent Bond∆EN = 0.4 – 1.7

The electron pair that makes up the bond is closer to the element that has the higher electronegativity.

Review

Intermolecular Forces

Three Types Hydrogen Dipole – dipoleLondon Dispersion (Van der Waals)

Based on weak attraction between molecules partial negative – partial positive

Types of Intermolecular Forces

Strongest intermolecular forceHydrogen “bond” (~ 10% of a covalent bond)Molecule must be polar (+ and – sides)H in one molecule is attracted to the N,O,F of

another molecule

Hydrogen Bond - bad choice of words – an attractive force , not a bond

Hydrogen “bonds”: attraction between H with N, O, F

Hydrogen bonds between water molecules.

Hydrogen bonds give unique properties to water.

Types of Intermolecular Forces

Other intermolecular forces Dipole-dipole – all polar molecules (weaker)

London dispersion forces – all molecules (weakest)

Dipole-dipole

Based on polarity of molecules

Found with polar covalent compounds

Use with elements other than H attracted to N, O or F

London Dispersion

Weakest Temporary polarity

Based on movement of the electrons around the nucleus

Impacts all molecules –

non-polar and polar

Factors that impact the state of matter

Intermolecular forces How do these attraction between molecules

form? Polarity (partial polarity) Shape Size

Polarity of Water

http://ed.ted.com/lessons/how-polarity-makes-water-behave-strangely-christina-kleinberg#watch

http://www.middleschoolchemistry.com/multimedia/chapter5/lesson1#polar_water_molecule

Short Tutorial with animations of polarity

Polarity http://

phet.colorado.edu/en/simulation/molecule-polarity

Use real molecules tabMolecular dipolesElectronegativity Electron density or electrostatic potential

Note: VSEPR – valence shell electron pair repulsion impacts shape

Shapes of Molecules

http://ed.ted.com/lessons/what-is-the-shape-of-a-molecule-george-zaidan-and-charles-morton

PHET simulation (?) http://phet.colorado.edu/en/simulation/mol

ecule-shapes

Predicting the Shape: VSEPR

Valence shell electron pair repulsion VSEPR theory

Non-bonding pairs of electrons (lone pairs) will push away (repel) from each other

Use Lewis structures to model VSEPRhttp://

www.green-planet-solar-energy.com/lewis-dot-structure.html

VSEPR: Lewis dot structure shows the pulling away of electron pairs

Ammonia

Water

Methane: CH₄

Ammonia: NH₃

Water: H₂0

Why is water unique? Why does ice float on water? https://

ed.ted.com/lessons/why-does-ice-float-in-water-george-zaidan-and-charles-morton

Hydrogen bonds -

Review: Energy in chemical reactions

Exothermic chemical reaction

Review: Energy in chemical reactions

Endothermic chemical reaction