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Chem101 > Final > Flashcards

Final Flashcards

1
Q

What is the fundamental difference between states of matter

A

The fundamental difference between states of matter is the distance between particles.

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2
Q

What is the order, displacement, and diffusion of solids

A

Solids: Ordered particles that are very close together, don’t change position, and have no diffusion.

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3
Q

what is the order, displacement, and diffusion of liquids

A

Liquids: Disordered particles that are close together, change positions and diffuse slowly.

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4
Q

What is the order, displacement, and diffusion of gases

A

Gas: Totally disordered particles that are very far apart, have lots of empty space between them, and have rapid diffusion.

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5
Q

What types of matter are compressible

A

Another characteristic is Compressibility. Solids and liquids are not compressible, applying a force can’t make them take up less space. However gases can be compressed into a smaller container.

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6
Q

What are the two antagonistic entities that determine the state of matter for a substance

A

The state of a substance at a particular temperature and pressure depends on two antagonistic entities:

  1. Attraction between particles: which acts to draw particles together
  2. The kinetic energy of the particles: which rises with temperature and acts to separate particles.
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7
Q

How stronger and intermolecular forces

A

The attraction between molecules are not nearly as strong as the chemical bonds that hold compounds together.

But it does control physical properties such as boiling and melting points, viscosity and vapour pressure.

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8
Q

What is the difference between intermolecular and intramolecular forces

A

Intermolecular forces = between molecules

Intramolecular forces = inside a molecule

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9
Q

what are the fundamental different types of particles that have intermolecular forces

A

The strength of an intermolecular force depends on whether or not the species are polar molecules, non-polar molecules, atoms, or ions.

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10
Q

How does polarity or change influence the strength of attraction

A

The more polar the molecule or highly charged the ion, the stronger the attraction from one species to another.

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11
Q

how is the intermolecular force related to distance

A

The intermolecular force is inversely proportional to the distance squared.

1/r^2

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12
Q

What are Ion-dipole interactions important

A

Ion-dipole interactions are an important force in solutions of ions and supramolecular chemistry. One of the strongest of the intermolecular forces because it is the attraction of a full charge for a partial charge.

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13
Q

What are Ion-dipole forces responsible for

A

these forces are responsible for ionic substance dissolving in polar solvents.

For a soluble solid, the sum of the anion-dipole and cation-dipole forces can overcome the lattice energy.

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14
Q

What are dipole-dipole forces

A

Polar molecules have permanent dipole moments. Partially negative ends of polar molecules are attracted to partially positive ends of nearby polar molecules.

Higher Dipole moment (D) usually results in higher Melting points and Boiling points.

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15
Q

what is hydrogen bonding

A

Due to an especially strong form of dipole dipole interactions called Hydrogen bonding, molecules like H$_2$O, HF, and NH$_3$ have high boiling points compared to other molecules in similar AH$_n$ forms.

The dipole-dipole interaction experienced when H is bonded to N, O or F are much stronger than other dipole-dipole interactions

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16
Q

Why does hydrogen bonding occur

A

Hydrogen bonding arises in part from the high electronegativity of N, O, and F.

When H is bonded to one of these very electronegative elements and the H nucleus is exposed.

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17
Q

How does Hydrogen bonding affect Ice

A

Ice has an open structure due to regulate hydrogen bonding which causes it to be less dense than liquid water.

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18
Q

What are London dispersion forces

A

All atoms and molecules are weakly attracted to one another through London dispersion forces, the attraction of an instantaneous dipole for an induced dipole.

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19
Q

Why do London dispersion forces occur

A

For an instant in time, electrons can be asymmetrically arranged around the nucleus such that the atom is polarized in that instant.

The instantaneous dipole induce a dipole in a neighbouring atom, causing mutual attraction.

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20
Q

Why kinds of molecules have London dispersion forces

A

London dispersion forces are present in all molecules, whether they are polar or non-polar.

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21
Q

How does size impact LDFs

A

London dispersion forces tend to increase in tandem with the size of an atom or molecule. bigger molecule = more electrons = more opportunities for instantaneous dipoles.

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22
Q

How does shape affect LDFs

A

The shape of the molecule affects the strength of dispersion forces:

Long, skinny molecules have stronger dispersion forces than short broad ones.

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23
Q

What type of force is present in situations where both polar molecules and ions are present

A

Ion-dipole forces

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24
Q

What type of force is present in situations where only ions are present

A

Ionic bonding forces

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25
Q

What type of force controls attraction when there are no ions or polar molecules

A

Dispersion forces

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26
Q

What type of force controls attraction when there are dipole but no H atoms bonded to N, O, or F atoms

A

Dipole-Dipole

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27
Q

What type of bonding controls attraction when H atoms are bonded to N, O, or F atoms

A

Hydrogen bonding

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28
Q

What is the order of bond strength in similar systems

A

Ionic bonding > Ion-Dipole forces > Hydrogen Bonding > Dipole-Dipole forces > Dispersion forces only

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29
Q

What balance affects the properties of a liquid

A

The properties of a given liquid depend on the balance between the

  • kinetic energy of particles
  • intermolecular attraction forces between particles
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30
Q

What is Viscosity

A

resistance to flow. Units = Pas = Kg/ms

Measured by how long it takes a steel ball to drop through a liquid over a specified distanced.

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31
Q

What makes a liquid more viscous

A

Liquids are more viscous when their constituent molecules:

  • have stronger intermolecular forces
  • are easily entangled
  • have higher molecular weight
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32
Q

What is surface tension

A

Created by Imbalance of forces at the top of a liquid.

Surface tension is related to the work require to increase surface area by a unit amount. Units = J/m$^2$

Bugs can float on water because the molecules on the surface assemble more tightly as they form fewer but stronger hydrogen bonds with the water molecules in the bulk.

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33
Q

What are Cohesive forces, and Adhesive forces

A

Cohesive force: binds liquid molecules to each other.

Adhesive force: binds liquid molecules to the surface.

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34
Q

what makes a concave surface

A

When the adhesive forces are stronger than the cohesive forces, the liquid forms a concave surface in the container. Ex water in a graduated cylinder.

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35
Q

what makes a convex surface

A

When the Cohesive forces are stronger than the Adhesive forces, the liquid forces a convex surface in the container. Ex mercury in a graduated cylinder.

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36
Q

what is Capillary action

A

Capillary action: strong adhesive forces draw liquid along sides of tubes and pores, cohesive forces pull along the rest of the liquid.

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37
Q

When does Evaporation occur

A

Evaporation occurs when energetic molecules or atoms near the surface of the liquid exceed the intermolecular forces to transition form the liquid to gas phase. The ease with which this happens dictates both the boiling point and the vapour pressure of the liquid.

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38
Q

What happens in an Open vs Closed system

A

In an Open system the molecules evaporate and are removed.

In a Closed system the molecules are evaporating and condensing at the rate in equilibrium.

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39
Q

When does Vapour pressure and Vaporization increase

A

Vapour pressure increases with temperature.
Vaporization is greater when the temperature is higher, the surface area is greater, or when the intermolecular forces are weaker.

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40
Q

what is Vaporization

A

Vaporization: Molecules escape the surface of the liquid into the gas phase.

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41
Q

When does boiling occur

A

Boiling occurs when vapour pressure = external pressure.

Normal boiling point: Temperature at which the liquids vapour pressure is 1 atmosphere (760mm Hg).

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42
Q

what are Volatile liquids

A

Volatile liquids evaporate easily and have a high vapour pressure at room temp.

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43
Q

what are phase changes

A

Changes in physical state, with no change in composition. Each phase change involves a change in the energy of the system.

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44
Q

What are Phase diagrams

A

Phase diagrams plot states of matter as a function of pressure and temperature.

45
Q

what can happen at low pressures

A

At low pressures gases can directly change to solids. And vice versa. Solid → Gas = Sublimation. Gas → Solid = Deposition

46
Q

what is a triple point

A

At a certain temp+pressure there is a “triple point”, where the condensing+Boiling line, Melting+freezing line, and Sublimation+Deposition line connect.

47
Q

what happens after the triple point

A

After the triple point there is a line where liquid turns to solid and vice versa.

There is also a gas←→ liquid line that eventually ends in an area where matter is considered a supercritical fluid.

48
Q

what is supercritical fluid

A

A Supercritical fluid has properties intermediate between a liquid and a gas.

49
Q

what is unique about water

A

Water shows an unusual behaviour trend at the solid liquid transition.

For one thing, solid is less dense than liquid.

And at higher pressure, water freezes and melts and lower temperature (the opposite of most materials where temp increases with pressure.

Waters Triple point is 272 K 101 kPa

and its critical point is 647 K and 22 MPa

50
Q

What are liquid crystals

A

Solids are characterized by their order, and Liquids are characterized by their lack of order.

Liquid Crystals are substances that exhibit one of more ordered phases at a temperature above the melting point.

51
Q

What is cholesteryl benzoate

A

The first systematic report of a liquid crystal was cholesteryl benzoate (in 1888).

At temperatures lower than 145º = solid, 145-179º = opaque liquid (Liquid Crystals), above 179º = clear liquid.

Cholesteryl benzoate passes through an intermediate liquid crystalline phase. It has some properties of liquids and some of solids. The liquid flows (liquid property) but has some order (solid property).

52
Q

what are liquid crystals like

A

Liquid Crystal molecules are usually long and rod-like. In normal liquid phases they are randomly oriented.

In the liquid crystal form molecules have some order, but not as much as solids.

53
Q

what three mains forms can liquid crystals exist in

A

Can exist in three main forms:

  • Nematic Liquid Crystals - are ordered along the long axis of the molecule only.
  • Smectic Liquid Crystals - are ordered along the long axis of the molecule and in one other dimension.
  • Cholesteric Liquid Crystals - are ordered along the long axis of the molecule and in twister layers.
54
Q

how does particle position play into solids

A

In solids, the intermolecular forces are strong enough to lock particles into fixed positions.

  • Crystalline solids have the particles arranged in a regular repeating patter. Ex metals, minerals, etc
  • Amorphous solids have those particles randomly arranged. Ex glass, wax, etc
55
Q

what are Molecular solids

A

Molecular solids are atoms or molecules held together by intermolecular forces. They are usually soft and have low melting points and low thermal and electrical conductivity.

Efficient packing of molecules is important (since they are not regular spheres). For example Benzene has a high melting point due to efficient packing.

56
Q

What are Metallic solids

A

Consist entirely of metal atoms; metallic bonding.

Valence electrons delocalized throughout the solid allow metallic solids to be good conductors of both heat and electricity. Metals can vary greatly in the strength of the bonding due to band theory.

57
Q

What are Ionic solids

A

Consist of ions held together by ionic bonds (i.e by electrostatic forces of attraction)

They are hard, brittle, and have high melting points.

The larger the charges (Q$_1$,Q$_2$) and the smaller the distance (r) between ions, the stronger the ionic bonding

The structure of the ionic solid depends on the charges on the ions and on the relative sizes of ions.

58
Q

what are covalent-network solids

A

Consist of atoms held together, in large networks or chains, with covalent bonds.

Have much higher melting points and are much harder than molecular solids.

Strong covalent bonds connect the atoms.

59
Q

what are the arrangement of Carbon atoms in diamond and graphite

A

each C atom is tetrahedral in a 3D array of atoms. This is why diamond is so hard and has a high melting point (3550ºC)

Strong covalent bonds connect the atoms within the layers of graphite. C-C 1.42 A.

The layers are held together by weak dispersion forces 3.35 A.

graphite is a good lubricant.

60
Q

what are crystalline solids

A

Crystalline solids include:

Molecular solids: units are molecules, low melting point. Ex Iodine

Ionic solids: units are Cations and Anions, high melting point. Ex Calcite (CaCO3)

61
Q

what are atomic solids

A

Nonbonding: held together by dispersion forces, low melting point. Ex Xenone

Metallic: held together by metallic bonds, low melting point. Ex Gold

Network Covalent: held together by constant bonds, high melting point. Ex quartz

62
Q

what are insulators

A

Many non-metals are insulators, i.e. electrons can’t flow freely through them. Insulators are characterized by having a large band gap (energy difference between a filled band and an empty band). Example include glass, air, rubber, wood, most plastics.

Ceramics are usually insulators, but some copper oxides are superconductors.

63
Q

What are semi-conductors

A

Silicon has the same structure as diamond, but a much smaller band gap:

Small enough that high temperatures or IR radiation can be enough to promote electrons from one band to another.

In a semiconductor the lower band is the Valence band, and the top one is the conduction band.

Usually some electrons much be promoted to the conduction band to work as a conductor.

64
Q

what are the average amounts of valence electrons in Inorganic semiconductors and what is doping

A

Inorganic compounds that are semiconductors tend to have an average of 4 valence electrons, and their conductivity may be increased by doping. → addition of controlled amount of an impurity to move away from average of 4 electrons. Ex a tiny bit of gallium added to silicon.

65
Q

what two types of semi conductor are made from doping

A

Doping yields different kinds of semiconductors:

n-type

  • Dopant atom has more valence electrons than the host atom
  • adds electrons to the conduction band

p-type

  • Dopant atom has fewer valence electrons than the host atom
  • leads to holes in the valence band
66
Q

what is silicon used for

A

Many modern devices rely on silicon wafers or “chips” containing complex patterns of semiconductors, insulators, and metal wires.

  • Si is abundant, cheap, and can grow enormous amounts of perfect crystals
  • It is non toxic
  • and can be chemically protected by SiO2
67
Q

what are solar energy cells

A

Semiconductors are also used in the production of solar energy cells. If you shine light with an appropriate wavelength on a semiconductor, electrons are promoted to the conduction band, making the material more conductive.

This is a property known as photoconductivity.

Solar cells are formed by joining n-type and p-type semiconductors.

Electrons are promoted by photons, generating a current.

68
Q

what are LEDs

A

Light-emitting diodes (LEDs) are used in many types of displays. the mechanism of action is the opposite of that involved in solar cells.

A voltage is applied and electrons in the conduction from the n-side combine at the junction with the holes from the p-side. Light is emitted whose photons have energy equal to the band gap.

69
Q

What are OLEDs

A

Organic LEDs (OLEDs) have some advantages over traditional LEDs.

Lighter, more flexible, and may be brighter and more energy efficient, made from conducting organic polymers.

Some problems with lifetime of devices, especially for blue (higher E)

Enabled the creation of curved and flexible displays.

70
Q

what are polymers

A

Many everyday materials are polymeric, involving simple organic molecules called monomers linked together to make chains, rings, networks, and folded constructrs. For example, cellulose is a polysaccharide (”polysugar”) chain of repeating glucose molecules.

71
Q

what is Polyglucose, what is Chitin

A

Polyglucose makes paper, and cotton.

If the related glucose unit has an amide group attached to it, the resulting polymer is called chitin.

Insect and crustacean exoskeletons are composite materials of chitin and calcium carbonate.

72
Q

how Is Febreze made

A

Humans have also used polysaccharides in imaginative ways. The air freshener Febreze contains a cyclic sugar called cyclodextrin, a ring shaped molecule that captures odor molecules.

73
Q

What is Lignin

A

Lignin is a polyphenolic crosslinked polymer found in wood. Small lignin molecules are called tannins.

Lignin is rigid and resistant to rot

complex cross-linked structure

74
Q

What is Bakelite

A

Bakelite, the first commercial plastic, is a phenolic resin.

75
Q

what is addition polymerization

A

Many synthetic polymers have a backbone of C-C bonds.

Ex: bunch of ethenes = polyethylene.

Coupling of monomers through multiple bonds is addition polymerization.

76
Q

what is HDPE

A

High density polyethylene (HDPE): bottles, grocery bags, milk jugs, recycling bins, playground equipment. (2)

77
Q

what is PVC

A

Polyvinyl chloride (PVC): Pipe, window profile, siding, fencing, lawn chairs, non-food bottles. (3)

78
Q

what is LDPE

A

Low density polyethylene (LDPE): Plastic bags, various containers, dispensing bottles, tubing. (4)

79
Q

what is PP

A

Polypropylene (PP): Auto parts, Industrial fibres, food containers, dish ware. (5)

80
Q

what is PS

A

Polystyrene (PS): Cafeteria trays, plastic utensils, coffee cup lids, toys, clamshell containers, packaging. (6)

81
Q

How are addition polymers formed

A

Addition polymers are formed by breaking the C=C π bond and forming a new C-C σ bond between the monomer and the polymer chain.

82
Q

Why are polymers hard to depolymerize

A

Because σ bonds are stronger than π bonds, addition polymers are hard to depolymerize

83
Q

what are plastics

A

Plastics are polymeric materials that can be formed into various shapes, usually with heat and pressure.

84
Q

what are thermoplastics

A

Thermoplastic materials can be reshaped (e.g. polyethylene)

85
Q

what are thermosetting plastics

A

Thermosetting plastic materials are shaped by an irreversible process (cannot be reshaped by melting and resolidifying)

86
Q

what is condensation polymerization

A

Condensation Polymerization: two molecules are joined to form a larger molecule by the elimination of a small molecule. e.g. water, methanol, acetic acid

ex: amine + carboxylic acid → amide + water

87
Q

what are copolymers

A

Polymers that are formed by two different monomers are called copolymers

88
Q

what are proteins

A

Proteins are formed of amino acid monomers (which contain both amine and carboxylic functional groups).

89
Q

how many amino acids are there

A

There are hundreds of amino acids known, though only 22 appear in the genetic code.

90
Q

what does the structure of amino acids allow them to form

A

One amino acid has both functional groups needed for a condensation reaction: can build a chain

91
Q

what does a chain of condensed amino acids form

A

A chain of condensed amino acids forms a polypeptide: that sequence will fold to form a protein

92
Q

what materials are polymeric proteins

A

Some natural materials are polymeric proteins, such as collagen (cartilage, tendons, skin), Keratin (nails, feathers, hair, scales), and fibroin (silk, spider thread).

93
Q

what can chemists make with amide linkages

A

Chemists also make polymers using amide linkages. Nylon was the first synthetic condensation polymer discovered, and other soon followed based on ester linkages.

Ex: Nylon 6 making clothing and string, Polyester Dacron making soda bottles, and clothing, and Lexan making bulletproof glass, safety glasses, and DVDs

94
Q

what do most synthetic and natural polymers consist of

A

Synthetic and natural polymers commonly consist of a collection of macromolecules of different molecular weights.

95
Q

what two regions of polymers usually have

A

Intermolecular forces between chains give order to polymers, crystallinity is order.

These kinds of polymers often have a crystalline region of order when the chains are all staked, and amorphous regions of disorder when the chains are random.

96
Q

what does mass affect in polymers

A

Intermolecular forces between chains give order to polymers, crystallinity is order.

These kinds of polymers often have a crystalline region of order when the chains are all staked, and amorphous regions of disorder when the chains are random.

97
Q

what do additives do

A

Polymeric properties may be modified by additives with lower molecular mass.

98
Q

what do plasticizers do

A

Plasticizers decrease interactions between chains and make polymers more pliable.

99
Q

what factors affect polymer properties

A

Factors that affect polymer properties include molecular properties, additives, and fabrication. Stretching or extruding a polymer can increase crystallinity.

100
Q

what makes a polymer more rigid

A

Cross-linked polymers are more rigid than straight-chain polymers:

e.g. vulcanization of natural rubber involves crosslinking of an unsaturated polymer with sulphur (S_8)

101
Q

what is vulcanized rubber

A

Volcanized rubber is more elastic and less reactive than natural rubber.

102
Q

how does Cross-linking affect natural polymers

A

Cross-linking of natural polymers make them harder, for example, the keratin in hair has less cross-linkage (disulphide bridges) than in finger nails.

103
Q

what 9 factors affect polymer properties

A
  • chain length
  • branching
  • polar groups
  • cross-linking
  • Double bonds, aromatic rings
  • substituents
  • Stereochemistry
  • Fabrication
  • Additives
104
Q

what makes something a nanomaterial

A

Nano = 10^-^9 nanomaterials have dimensions of 1-100 nm

105
Q

what are Nanoscale Semiconductors:

A

Semiconductor particles with 1-10 nm diameters are called quantum dots. Band gaps change substantially with size in this range.

Fluorescent CdSe Quantum dots: Increasing particle size and decreasing band gap leads to more red.

106
Q

what are Nanoscale metals

A

metals in the 1-100 nm size range are interesting nano-materials

  • known for centuries that finely divided metals have strange properties.
  • Medieval craftsmen dispersed preciously metals in molten glass to make deep reds and yellow colours.
107
Q

what are Carbon Nanotubes

A

Carbon Nanotubes:

Sheets of graphite rolled up and capped at one or both ends.

  • 1000s of nm long but only 1nm wide
  • Single-walled and multi-walled tubes
  • interesting electronic and structural (mechanically very strong) properties
  • promising for use as “nanowires”
108
Q

What is Graphene

A

Graphene:

A single unrolled sheet of graphite

  • made from peeling single sheets from graphite using scotch tape
  • A “semi-metal” with record thermal conductivity
  • Can sustain current densities 6 times that of copper.

Chem101 (3 decks)

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