Unit 11: States of Unit 11: States of MatterMatter

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Types of Covalent BondsTypes of Covalent Bonds

Polar Covalent BondPolar Covalent Bond– ee-- are shared unequally are shared unequally– asymmetrical easymmetrical e-- density density– results in partial charges (dipole) results in partial charges (dipole)

Nonpolar Covalent BondNonpolar Covalent Bond– ee-- are shared equally are shared equally– symmetrical esymmetrical e-- density density– usually identical atoms usually identical atoms

Types of Covalent BondsTypes of Covalent Bonds

If If ΔΔEN is:EN is: Bond type is:Bond type is:

< 0.4< 0.4 Nonpolar covalentNonpolar covalent

0.4 0.4 << ΔΔ EN EN << 1.7 1.7 Polar covalentPolar covalent

> 1.7> 1.7 IonicIonic

Given: Electronegativities of these elements

H = 2.2 C = 2.55 N = 3.04 O = 3.44 F = 3.98Na = 0.93K = 0.82 P = 2.19 S = 2.58 Cl = 3.16

Determine bond type for the following bonds:

H – H __________ H – O ___________H – C __________ Na – Cl ___________

Take the absolute value of the difference!

Intermolecular Forces Intermolecular Forces (IMF)(IMF)

Intermolecular Forces Intermolecular Forces (IMF)(IMF)

Attractive forces Attractive forces betweenbetween molecules. molecules.

Much weaker than Much weaker than

chemical bondschemical bonds

withinwithin molecules molecules ((INTRAmolecular forces.INTRAmolecular forces.

London Dispersion ForcesLondon Dispersion ForcesLondon Dispersion ForcesLondon Dispersion Forces London dispersion forcesLondon dispersion forces

– Exist in Exist in allall atoms and atoms and moleculesmolecules

– Electrons within atoms are Electrons within atoms are constantly moving around. constantly moving around. Sometimes they are not Sometimes they are not disbursed evenly around disbursed evenly around the nucleus. the nucleus.

– When atoms are close to When atoms are close to each other, they are each other, they are attracted due to the attracted due to the temporary area of partial + temporary area of partial + and - charges (temporary and - charges (temporary dipoles) produced.dipoles) produced.

London Dispersion ForcesLondon Dispersion ForcesLondon Dispersion ForcesLondon Dispersion Forces

Dipole-Dipole ForcesDipole-Dipole ForcesDipole-Dipole ForcesDipole-Dipole Forces

-Attraction between two PERMANENT dipoles

-Polar molecules ONLY.

-Medium strength

-Stronger when molecules are closer together

Types of IMFTypes of IMF Types of IMFTypes of IMF

Dipole-Dipole ForcesDipole-Dipole Forces

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View animation online.

Hydrogen BondingHydrogen BondingHydrogen BondingHydrogen Bonding– Special kind of dipole-dipoleSpecial kind of dipole-dipole– Occurs between molecules that Occurs between molecules that

have an have an HH bonded to either bonded to either OO, , NN, or , or FF..

– StrongestStrongest– Not chemical bondingNot chemical bonding

Hydrogen BondingHydrogen BondingHydrogen BondingHydrogen BondingAnimation of water molecules being attracted to each other.

IMF and Boiling PointIMF and Boiling Point The stronger the IMF, the higher the The stronger the IMF, the higher the

boiling point.boiling point. MoleculMolecul

eeIMF (s) presentIMF (s) present Molar Mass Molar Mass

(g/mol)(g/mol)Boiling Point Boiling Point

((ooC)C)

CHCH44 16.0516.05 - 164- 164

HClHCl 36.4636.46 - 85- 85

HH22OO 18.0218.02 100100

London Disp.

London Disp.

Dipole-DipoleLondon Disp./Dipole-Dipole/Hydrogen Bonding

DensityDensity

CompressibilityCompressibility

The more empty space between particles, the easier it is to compress it.

Solids are not easily compressed, liquids a little bit, gases a lot.

Liquid PropertiesLiquid PropertiesLiquid PropertiesLiquid Properties ViscosityViscosity

– Resistance to flowResistance to flow

Viscosity Demo

Water

Oil

Liquid PropertiesLiquid PropertiesLiquid PropertiesLiquid Properties Surface TensionSurface Tension

– attractive force between particles in a liquid that attractive force between particles in a liquid that minimizes surface area. Creates a SURFACE that minimizes surface area. Creates a SURFACE that keeps the liquid together.keeps the liquid together.

Detergents/SoapDetergents/Soap

Oils don’t mix with Oils don’t mix with water.water.– Fats/oils are non polarFats/oils are non polar– Water is polarWater is polar– LIKE DISSOLVES LIKELIKE DISSOLVES LIKE

Soaps and detergents Soaps and detergents disrupt the hydrogen disrupt the hydrogen bondingbonding between the between the water molecules.water molecules.

A A micelle micelle is formed. is formed. (Detergent wraps around (Detergent wraps around grease particle and it can be grease particle and it can be mixed with water.)mixed with water.)

Cohesion and AdhesionCohesion and Adhesion

CohesionCohesion is the force of attraction is the force of attraction between identical moleculesbetween identical molecules in a in a liquid (cohesion is a result of liquid (cohesion is a result of intermolecular forces). intermolecular forces).

AdhesionAdhesion is the force of attraction is the force of attraction between liquid molecules and a between liquid molecules and a solidsolid that is touching them. that is touching them.

Liquid PropertiesLiquid PropertiesLiquid PropertiesLiquid Properties

water mercury

Meniscus of water in a glass tube is concave: adhesion > cohesion

Meniscus of Hg in a glass tube is convex: cohesion > adhesion

PROPERTIES OF SOLIDSPROPERTIES OF SOLIDS

Density: Solids are denser than Density: Solids are denser than their liquid form.their liquid form.

– EXCEPT: wax, cork, iceEXCEPT: wax, cork, ice In these solids, the molecules are spaced In these solids, the molecules are spaced

farther apart than in their liquid form so they farther apart than in their liquid form so they float.float.Ice cork wax

Crystalline vs. Crystalline vs. Amorphous:Amorphous:

A A crystallinecrystalline solid has solid has particles which particles which are arranged in are arranged in an orderly, an orderly, geometric, 3-D geometric, 3-D structure.structure.

– Examples: Examples: sodium chloride, sodium chloride, ice, gems and ice, gems and mineralsminerals

Types of SolidsTypes of SolidsTypes of SolidsTypes of Solids

Amorphous(SiO2 - glass)

In an amorphous solid, the particles are not arranged in any particular pattern.

Examples: rubber, plastics.

Phase ChangesPhase ChangesT

em

pe

ratu

re E. Q=mCΔT

D. Q= mHv Tb B. Q =mHf

C. Q=mCΔTTm A. Q= mCΔT

Thermal Energy (Heat)

Thermal Energy (heat)Thermal Energy (heat)

Phase Changes:Phase Changes:– B and D represent phase changesB and D represent phase changes– Occur at Occur at constant temperatureconstant temperature

Temperature ChangesTemperature Changes– A,C, and EA,C, and E– Temp is changingTemp is changing– Sloping portion of the graphSloping portion of the graph

Thermal Energy (heat )Thermal Energy (heat ) What is happening at each part of the graph:What is happening at each part of the graph: A. A. Substance is a solid. Can heat it up or cool Substance is a solid. Can heat it up or cool

it down along this line.it down along this line. B.B. Phase change: solid-liquid. The Phase change: solid-liquid. The

temperature at B (temperature at B (TmTm) is the ) is the melting melting (freezing) point(freezing) point. .

C.C. Substance is a liquid. Can heat it up or cool Substance is a liquid. Can heat it up or cool it down along this line.it down along this line.

D.D. Phase change: liquid-gas. The temperature Phase change: liquid-gas. The temperature at D (at D (TbTb) is the ) is the boiling (condensation) pointboiling (condensation) point..

E.E. Substance is a gas. Can heat it up or cool it Substance is a gas. Can heat it up or cool it down along this line.down along this line.

Heat CalculationsHeat Calculations

Q = m c Q = m c ∆∆ T T– Q = heat or thermal energy in Joules (J) or Q = heat or thermal energy in Joules (J) or

calories (cal)calories (cal)– m= mass in grams (g)m= mass in grams (g)– C = specific heat in J/(g C = specific heat in J/(g ooC) or cal/(g C) or cal/(g ooC)C)– ∆∆T= T= changechange in temperature in oC in temperature in oC

Heat CalculationsHeat Calculations

Q =mHQ =mHff

– Q = heat or thermal energy in Joules (J) or Q = heat or thermal energy in Joules (J) or calories (cal)calories (cal)

– m= mass in grams (g)m= mass in grams (g)

– HHff = Heat of fusion (J/g or cal/g); use for = Heat of fusion (J/g or cal/g); use for liquid-solid phase changeliquid-solid phase change

Heat CalculationsHeat Calculations

Q =mHQ =mHvv

– Q = heat or thermal energy in Joules (J) or Q = heat or thermal energy in Joules (J) or calories (cal)calories (cal)

– m= mass in grams (g)m= mass in grams (g)– Hv = Heat of vaporization (J/g or cal/g); Hv = Heat of vaporization (J/g or cal/g);

use for gas-liquid phase changeuse for gas-liquid phase change

Things to rememberThings to remember

You can move from left to right or right You can move from left to right or right to left along the curve. to left along the curve.

If you move left to right:If you move left to right:– all the processes are all the processes are endothermicendothermic (heat (heat

must be supplied). must be supplied). – Your answer for heat calculations will be Your answer for heat calculations will be

positive.positive.

Things to rememberThings to remember

If you move right to left:If you move right to left:– all the processes are all the processes are exothermicexothermic (heat (heat

is removed/released). is removed/released). – Your answer for heat calculations will be Your answer for heat calculations will be

negativenegative. . You have to write in the You have to write in the negative, but you solve the problem negative, but you solve the problem the same way!the same way!