Solids,Liquids and other IMA’S

Phase Differences Solid Solid – definite volume and shape; particles packed in fixed positions; particles are not free to move Liquid Liquid – definite volume but indefinite shape; particles close together but not in fixed positions; particles are free to move Gas 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 --

Intermolecular Forces (IMF)  Dipole-dipole attraction  Hydrogen bonds  London Dispersion forces Forces of attraction between different molecules rather than bonding forces within the same molecule.

Forces and Phases oSubstances with very little intermolecular attraction exist as gases oSubstances with strong intermolecular attraction exist as liquids oSubstances 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 one Dipole – 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 Bonding A special type of dipole-dipole bonding that is extremely strong. Occurs when there is an attraction between Hydrogen and… 1. Nitrogen 2. Flourine 3. Oxygen IMF – type two BUT WHY IS HYDROGEN SO SPECIAL?

Lets review Dipole-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 another Why 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 pulled Away, what remains? Just a proton With an exposed proton, the positive charge is strong so the IMF is stronger.

QUICK RECAP What 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 3 If 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 STRENGHTS MOST ELECTRONS

Solids,Liquids and other IMA’S

Which IMA are stronger? A - H-Bonding B - Di-Di C - LDF D - All same strength

Which molecules have a stronger IMA? A - KCl B - H 2 O C - SiH 4 D - C 2 H 6

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-Bonding B - Di-Di C - LDF D - All same strength

Which molecule will boil first? A - HCl B - CO 2 C - NH 3 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 -CH 3 OH B - HCl C - H 2 O D - CH 4

Which molecule has the strongest IMA’s? A -CH 4 B - C 3 H 8 C - C 5 H 12 D - C 7 H 16

Which molecule will cause the greatest lose in temperature when in evaporates? A -CH 4 B - C 3 H 8 C - C 5 H 12 D - C 7 H 16

HW ASA – 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 tension If 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.

So can you explain 1. Why belly flops hurt 2. 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 action The ability of a liquid to flow against gravity. Due to two forces This 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 Solids  General type 2: Most common BY FAR (99%) Crystalline Solids: highly regular arrangement of their components [NaCl, pyrite (FeS 2 )]. 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 H 2 O, I 2, C 3 H 7 OH 3. Network Solids – aka Covalent crystals - Very small category only includes Diamond (C), Graphite (C), SiO 2, and WC - Very small category only includes Diamond (C), Graphite (C), SiO 2, and WC 4. Metallic Solids – any pure metal example 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 (FeS 2 ) - examples: NaCl, pyrite (FeS 2 ) IONIC BONDING between atoms 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. C 6 H 12 O 6 / C 12 H 22 O 6 ) COVALENT BONDING between atoms

Types of Crystalline Solids 3.Network Covalent: There are only a few in this caterory. Graphite – C Diamond – C Quartz – SiO 2 WC, SiC Highest 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 hard to 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.

Recap SOLID strength 1. Network Solids – Si and C 2. Metallic solids 3. Ionic solids 4. 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 Triple point Super cooled Helium I

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