3.1-3.3 Quiz Flashcards
London Dispersion Forces(LDFs)
- Definition
- What type of substances have LDFs?
- The result of Coulombic interactions between temporary, fluctuating dipoles.
- All substances have LDFs. They are the only force in nonpolar molecules or single nonmetal atoms.
What is the strongest IMF between large molecules?
LDFs
How does the polarizability of a molecule increase and why?
The polarizability of a molecule increases when the number of electrons in a molecule increases because larger atoms have more loosely held electrons in contrast to smaller atoms with tightly bound electrons.
Dipole-dipole interactions
- When do they occur?
- What substances have dipole-dipole?
- How do they increase?
- They occur between polar molecules.
- All polar molecules have dipole-dipole.
- When the difference in electronegativity is greater then the dipole is stronger
Are polar molecule interactions greater than nonpolar molecule interactions? Why or why not?
Yes because polar molecule interactions act in addition to LDFs.
Hydrogen bonding
- Where does it exist?
- The hydrogen has to be covalently bonded to NOF and then bonded to NOF through an intermolecular force. Technically it has to occur between molecules not within, but if it occurs within it needs to be far apart.
Intermolecular forces vs intramolecular forces
Inter- between molecules(H2 —- H2)
Intra- between atoms( H- - - O - H—-O)( dotted lines)
Weakest to strongest IMFs
Molecular(LDFs, Dipole-Dipole, Hydrogen Bonding), Ionic/Metallic, Covalent Network
Ionic interactions
- Description/Definition
- In what substances do these occur?
- When are ionic bonds stronger?
- Metal and nonmetal atoms form a lattice of alternating positive and negative ions held
together by ionic bonds - When metals bond with nonmetals when they lose or gain electrons to form ions.
- They are stronger when the charges are larger and the ions are smaller.
Covalent network
- Description/Definition
- Name the atoms that will have a covalent network.
- How do these increase?
- Nonmetal atoms form a lattice structure held together with covalent bonds.
- (BASICALLY ATOMS WITH C AND METALLOIDS(LIKE SILICON, GERMANIUM, BORON, ETC.)) C(diamond), C(graphite), C60, SiO2, SiC
- When there are more covalent bonds formed(two nonmetals)
Polarizability
The ability of an atom to form a temporary or induced dipole
When going down the list of halogens they change in state from gas to liquid to solid. Why does this happen?
This is because the LDFs increase and the LDFs increase due to the increase in electrons. Also, larger molecules will have stronger LDF because the increase in electrons increases their polarizability.
Name the way LDFs increase.
They increase with increasing contact area(meaning the bigger it is(more electrons it has)) between molecules and with increasing polarizability of the molecules. Also, long thin molecules have more surface area, stronger LDFs, and stronger polarizability. Short round/compact molecules have less surface area, weaker LDFs, and weaker polarizability. Lastly, the presence of double or triple bonds.
How are LDFs caused?
They are caused by the motion of electrons within an atom or molecule. As the electrons move around with the atom, the electrons sometimes become unequally distributed and the atom or molecule creates a temporary dipole because there is an excess of negative charge in one place and an area that is partially positive because it is deficient in electrons. This is a short lived thing which is why this is such a weak force.
Hydrocarbon
Only hydrogens and carbon
The amount of energy needed to melt a substance at its melting point is called the heat of fusion and for
water the value is 6.01 kJ/mol. The amount of energy needed to vaporize a substance at its boiling point is
called the heat of vaporization and for water the value is 40.7 kJ/mol. Use the relative distances in the
states of matter and the concepts intermolecular forces to explain the difference.
Solid to a Liquid is a slight distance increase, however Liquid to a Gas is a large distance increase because spreading the molecules apart takes a lot of energy.
Surface tension
ability of the surface of a liquid to resist an external force
Viscosity
resistance to flow
Heat of Vaporization
energy required to convert a liquid to a gas
Vapor pressure
Pressure exerted by a gas when it is at equilibrium with its liquid(in a closed container)
Ionic solid properties
Due to strong interactions between ions, ionic solids have
- High Melting Points(bc of strong coulombic attractions)
- Hard and brittle
- Low Vapor Pressure
- Poor conductors of heat and electricity unless they are melted bc ions need to be able to freely flow and move to conduct electricity and they cannot do that unless they are melted
Covalent properties
Covalent bonds are relatively strong, so they have
- High melting point
- Hard/Brittle and Strong
- Poor conductors of heat and electricity bc electrons are pulled tightly in the covalent bonds
- Only formed from nonmetals
Molecular solid properties
- Low Melting Point bc of weak IMFs
- Soft
- Poor conductor of heat and electricity because the electrons are held tightly in the covalent bonds
- Composed of distinct, individual units of covalently-bonded molecules attracted to each
other through relatively weak IMFs. - Composed of nonmetals
Metallic solid properties
- Good conductors of electricity and heat, due to the presence of free flowing valence electrons.
- Malleable and ductile, due to the ease with which the metal cores can rearrange their structure
- Composed of metallic elements
Substitutional Alloy
- How are the malleability and ductility affected?
An atom of similar size that substitutes for another atom in lattice. It remains malleable and ductile.
Interstitial Alloy
- How are the malleability and ductility affected?
A smaller atom that fills the space between larger atoms. The smaller atoms tend to make the lattice more rigid which decreases malleability and ductility.
What do large biomolecules functionality and properties depend on?
They depend on the shape of the molecule
Practice I Do 3.2 #1 and you do #6 and 3.3 you do #1, 2
Brief description of Molecular solids
Nonmetal atoms form molecules with covalent bonds. The molecules are held together in a
solid by intermolecular forces of attraction.
Go through these solids(IONIC, COVALENT NETWORK, MOLECULAR, METALLIC) and list the bonds/forces that are broken when this solid melts and describe the particles that make up the liquid when it is melted.
Ionic- ionic bonds/ ions
Covalent- covalent bonds/ atoms
Molecular- IMFs/ molecules
Metallic- metallic bonds/ atoms
Go through 3.1 quiz on ap classroom
Properties of solids when crystalline
- Strong interactions between particles(why we cannot walk through walls)
- Definite shape and volume(lined up in rows and tightly packed)
- Vibrational degree of freedom(solids are constantly vibrating down at the particulate level)
- Limited motion(the particles cannot move freely only vibrate) bc the particles are packed so closely together
- Cannot be compressed due to minimal space between particles
- Fixed shape
How is graphite different than most covalent networks?
Graphite is very soft because the layers can easily slide past each other because of the weak IMFs. It is also a great conductor of electricity because delocalized electrons flow across the graphite sheets.
Why is aluminum used in pans and wires?
Because it is a great conductor of heat and electricity and can get hot pretty quick
What does the shape of an amorphous solid look like?
It does not have an orderly arrangement like crystalline solids do
Properties of liquids
- Atoms in close contact but not as tight and packed as solids js a little less
- Able to move past each other and roll around js a little
- Take shape of their container
- Unable to be compressed because the particles are close together
- Molecules at the surface are able to evaporate
- Fixed volume
The solid and liquid phases for a particular substance typically have similar _________ because, in both
phases, the constituent particles are __________
molar volume; in close contact at all times
Properties of Gases
- Particles in constant motion
- Neither a definite volume or shape(bc of constant motion of particles)
- Easily compressed
- Take the shape of their container bc particles can move freely
- Little to no attraction between molecules
- Large space between them
What are the frequency of a gas’ collision based on?
Their frequencies of collision and the average spacing
between them are dependent on temperature, pressure, and volume.
Why do gases follow the ideal gas law?
Bc gas particles are spaced far apart with minimal IMFs
When are gases more ideal?
With low pressures and high temperatures because at high temperatures they move fast and with low pressure they are far apart so IMFs are minimized.
Why does vapor pressure decreases as IMFs increase?
Bc things with high vapor pressure easily evaporate, so if attractive forces are getting stronger then they cannot easily evaporate and we need a low vapor pressure
Ion-dipole interactions
- When do they occur?
- What is the strength of these compared to other interactions?
- How do these increase?
- Present between ions and polar molecules
-They are stronger than dipole-dipole forces and hydrogen bonding - The strength increases with large charges and smaller ions and more polar molecules.
Metallic interactions
- Description/Definition
- In what substances do these occur?
- Why do these occur?
- How do these increase?
- Metallic atoms with very loose electrons for a lattice of nuclei held together by a sea of electrons, or metallic bonds.
- Only metal atoms
- These occur because multiple metallic cations are attracted to a delocalized sea of valence electrons.
- When there are smaller metallic cations and when there are more valence electrons.
Know all of these trends: If an IMF is increasing
- Boiling/Melting/Freezing Point
- Vaporization
- Vapor Pressure
- Viscosity
- Surface Tension
- Solubility
- Lattice Energy
- Increases
- Increases
- Decreases
- Increases
- Increases
- Decreases
- Increases
Volatility
Ease of evaporation
Do practice problems in 3.2 video 2
