Solids,Liquids

and other IMA’S

Phase Differences

Solid – definite volume and shape; particles packed in fixed positions; particles are not free to move

Liquid – definite volume but indefinite shape; particles close together but not in fixed positions; particles are free to move

Gas – neither definite volume nor definite shape; particles are at great distances from one another; particles are free to move

INTRAmolecular Forces – aka bonds

Forces between ATOMS

INTERmolecular Forces –Forces between Molecules

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Intermolecular Forces (IMF)

Dipole-dipole attraction

Hydrogen bondsLondon Dispersion

forces

Forces of attraction between different molecules rather than bonding forces within the same molecule.

Forces and Phases

o Substances with very little intermolecular attraction exist as gases

o Substances with strong intermolecular attraction exist as liquids

o Substances with very strong intermolecular (or ionic) attraction exist as solids

To change the state of matter, You add energy (heat) to the compound. This energy (heat) breaks the IMF’s not the bonds.

So which is weaker, Intra (bonds) or Inter (molecules) molecular forces?

The Intermolecular forces are only 1% as strong as Intramolecular forces.

IMF – type oneDipole – Dipole Interactions

Occur between polar molecules only.Electronegativity creates a partial positive and partial negative.

The δ+ is attracted to the δ- of another molecule.

This is a dipole-dipole IMF. It repeats itself in all directions

Hydrogen BondingA special type of dipole-dipole

bonding that is extremely strong.Occurs when there is an attraction

between Hydrogen and… 1. Nitrogen2. Flourine3. Oxygen

IMF – type two

BUT WHY IS HYDROGEN SO SPECIAL?

Lets reviewDipole-dipole only occurs in polar

molecules. What is happening to the electrons in a polar bond?

- Electrons are being pulled away from one atom towards anotherWhy only H-F, H-N, H-O?

- Those atoms are the most electronegative so they pull the shared electrons the most.So why is H-F a stronger bond than Li-F?

- lets look at the hydrogen atom in detail

Hydrogen

One proton and one electron

If it’s only electron is pulledAway, what remains?

Just a proton

With an exposed proton, the positive charge is strong so the IMF is stronger.

QUICK RECAPWhat type of molecules have dipole

dipole?Which is stronger, intramolecular or

intermolecular?What molecules make up a hydrogen

bond?Which state of matter has the weakest

IMA’s?What are two reasons H-bonds are so

strong?

IMF – Type 3If you do not have a polar molecule,

you have London Dispersion Forces (LDF)– aka dispersion– aka Vanderwahls forces

Occurrs in nonpolar molecules when the electrons randomly become shared “unevenly”

The strength of the bonds are

Strongest – Hydrogen bonding- Dipole-dipole

Weakest - LDF

The stronger the IMF, the energy needed to break the attractions.

So compounds with strong IMF’s have melting points and/or boiling points

If two molecules are nonpolar, the stronger IMF will go to the molecule with

MORE

HIGHER

YOU NEED

TO KNOW

THE

ORDER OF

THE

STRENGHT

S

MOST ELECTRONS

Solids,Liquids

and other IMA’S

Which IMA are stronger?

A - H-BondingB - Di-DiC - LDFD - All same strength

Which molecules have a stronger IMA?

A - KClB - H2O

C - SiH4

D - C2H6

What is boiling?

How does the temperature at which something boils

relate to the strength of its IMA’s?

Which molecule will require the most energy

to boil?A - H-BondingB - Di-DiC - LDFD - All same strength

Which molecule will boil first?

A - HClB - CO2

C - NH3

D - LiBr

How does something evaporate?

How does the strength of its IMA’s impact the rate at

which something evaporates?

Which molecule evaporate the fastest?A - CH3OH

B - HClC - H2O

D - CH4

Which molecule has the strongest IMA’s?

A - CH4

B - C3H8

C - C5H12

D - C7H16

Which molecule will cause the greatest lose in

temperature when in evaporates?

A - CH4

B - C3H8

C - C5H12

D - C7H16

HWASA – Evaporation Lab

Solids,Liquids

and other IMA’S

What are the properties of liquids?

1. The molecules take the shape of their container with out changing their volume (pouring water into a glass).

2. Moderate IMF’s. Molecules are attracted to each other but can move and flow.

3. Has a few properties that gases & solids do not have.

Surface tensionIf you are a molecule in

the middle, you are being pulled in every direction by an IMF from surrounding molecules. What if you are on the surface though?

Molecules on the surface are only sharing their attraction between about half of the number of molecules so each IMF is stronger and harder to break.https://www.youtube.com/watch?v=45yabrnryXkhttps://www.youtube.com/watch?v=aeqHEyhBosw

So can you explain 1. Why belly flops hurt2. Why water beads up

1. The IMF’s on the surface are stronger so with a belly flop, you have a large surface area and you have to break all the surface bonds with are resistant and that is why it hurts. 2. The water molecules are more attracted to themselves than the other surface. So the water will “move” to surround itself with other water molecules and minimize the contact with the surface causing the water to “bead”.

Capillary actionThe ability of a liquid to

flow against gravity.Due to two forcesThis is why water forms a

meniscus in a tube.

This is also how plants transport water and minerals throughout the root and stems system.

Viscosity

The resistance of a liquid to flow.The stronger the IMF’s, the

the viscosity of the liquid.

Which has stronger IMF’s water or honey?How do you know?

HIGHER

Solids & Liquids

Types of Solids

General type 1:

Amorphous solids: considerable disorder in their structures (glass and plastic).

Types of SolidsGeneral type 2: Most common BY FAR

(99%)Crystalline Solids: highly regular

arrangement of their components [NaCl, pyrite (FeS2)].

IONIC BONDING between

atoms

Classes of Crystalline Solids

1. Ionic Solids – any metal and nonmetal example NaCl, CuO,

2. Molecular Solids - When nonmetals freeze into solids

example H2O, I2, C3H7OH

3. Network Solids – aka Covalent crystals - Very small category only includes

Diamond (C), Graphite (C), SiO2 , and WC

4. Metallic Solids – any pure metalexample Na, Fe, Al. Cu, etc.

1. IONIC Solids: Formed between a metal and a nonmetal. - Conduct electricity and heat when melted- High melting point- somewhat brittle

- examples: NaCl, pyrite (FeS2)

IONIC BONDING between

atoms

Types of Crystalline Solids

Types of Crystalline Solids

2. Molecular Solids: Large molecules made of nonmetals.

Typically have dipole-dipole or LDF when they are liquids.

Usually large molecules (ex. C6H12O6 / C12H22O6)

COVALENT BONDING between

atoms

Types of Crystalline Solids

3. Network Covalent: There are only a few in this caterory. Graphite – C

Diamond – CQuartz – SiO2

WC, SiCHighest Melting points and strongest

IMF’s of any substances on earth. Why?Because both Si and C like to make so many covalent bonds (4 around each atom). These add together to create very strong solids.

4. Metallic solids

Which has a higher melting point: Aluminum or Water?

Which has stronger IMF’s: Aluminum or Water?

If a molecule has stronger IMF’s, it should be easy or hardto bend.

So why can we mold aluminum (malleable and ductile) if

its IMF’s are so strong? Contradicts itself?

All About the way metals bond

Pure metal atoms get together and just donate all their electrons to the “pool”

This is known as the metallic sea of electrons.

Atoms do not “have” any electrons but are completely surrounded by all the donated electrons (Pot Luck Dinner)

Moving (bending) the atoms around the sea is easy but tearing one off is very hard.

RecapSOLID strength

1. Network Solids – Si and C2. Metallic solids3. Ionic solids4. Molecular crystals – Rank depending upon type of IMF

These are not 100%

accurate but a decent

guide to determine

strength of solids

Phase Changes!

Water phase

changes

Temperature remains __________during a phase change.

constant

Where is the liquid line?

What is happening on line DE?

If you heat the solid to 70 degrees, what can we expect to happen?

Line CD

The gas is beginning to boil

Melting

Phase Diagram Represents phases as a function of temperature and pressure. Critical temperature: temperature above which the vapor can not be liquefied. Critical pressure: pressure required to liquefy AT the critical temperature. Critical point: critical temperature and pressure

Phase changes

Triple point 1

https://www.youtube.com/watch?v=BLRqpJN9zeA

Triple point 2 https://www.youtube.com/watch?v=XEbMHmDhq2I

Super cooled Heliumhttps://www.youtube.com/watch?v=2Z6UJbwxBZI

If the substance is heated to 200 K at 1 atm, which state would it be?

What is the maximum temp with a pressure of 1 atm and still be a solid?

If pressure is held constant at 3 atm and heated from 100 K to 300K, what is happening?

Gas

197.4K

Sublimation – solid to a gas