Exam 3 - Principles of Chemistry

what is a boiling point? high bp = ?

liquid turning into a gas ; high bp = higher melting point

what is vapor pressure? low vp = lower ?

gas leaving a liquid surface which breaks liquid - liquid IMFs ; volatility

what is viscosity?

how easily a liquid flows (high viscous liquids flow slowly)

what is apart of IMF’s? relative strength

stronger intermolecular attrations which means harder to break and higher heat/energy)

relative strength depends on: bond polarity, molecular polarity, polarizability

what are the 3 parts of stronger IMF’s? EXPLAIN boiling points / vapor pressure / viscosity

higher BP

lower vapor pressure:

higher viscosity

define intermolecular forces and examples

interactions between molecules arise from their charged regions (from electrons and protons) that ATTRACT or REPEL each other with forces that vary on the distance

• hydrogen bonding, london dispersion

define intramolecular forces

hold atoms together within a single atom

• covalent and ionic bonds

which are stronger? intra/inter

intra

what is the range for polar covalent bonds?

>2

more susceptible to being polarized = _____ dispersion forces

stronger

polarizability is generally larger with ____ electrons over a ____ volume and a ____ exposed area

more, larger, more

do all molecules have dispersion forces and induced dipole moments?

yes

which forces have the largest contribution to IMFs between atoms and molecules?

dispersion forces (induced dipoles)

which orientation would you expect dispersion interactions to be stronger?

the larger the contact area of interaction, the stronger the IMF

what are the two forces that make up total IMF’s?

dispersion and dipole dipole

Just because it is polar doesn’t automatically mean higher. You must count electrons. T/F

true

IMF polar bonding interaction is ____ (is/is not) a covalent bond

not

what effect do branches have on IMF?

the presences of branches reduces the effective contact area over which molecules can interact → decreasing IMFs

what happens in lower IMF? melting point, BP, viscosities, volatilities

lower

• melting point, boiling point, viscosities

higher

• volatilities (substance ability to transition)

what are ideal conditions for mixing?

lower PE, more configurations

Particles are ____ likely to adopt those states where the IMFs between them are stronger (lower PE)

more

Particles are ____likely to adopt states with more configurations.

more

explain exothermic vs endothermic

exothermic: energy released - endothermic: energy taken in

in a substance that mixes, what would you expect the heat of mixing to be greater than zero?

exothermic (lowers E)

Since mixing is exothermic, adding heat would ___ improve miscibility. (maybe

not

what is the effect of increasing or decreasing temperature on solubility and miscibility (mixing)?

generally - solubility and miscibility increases with increasing T (ususally true but are independent of eachother)

when mixing is favored, it is ____ (forward/backward)

forward

when UM and M are even, temperature (always/never) has an impact

never

define monomer

a repeating subunit used to make a polymer

define polymer

a large molecule made of repeating subunits

define macromolecule

a molecule with a very high molecular weight

what factors affect the properties of a polymer?

chain length, intermolecular forces, extend of chain branching

in a condensation reaction, what do you remove?

H2O (“water elimination”)

explain the importance of branching and chain length

branches create more structures within chains (disrupt IMFs)

longer chain length = higher density

what is density in regards to chain length and branching?

• the amount of IMFs in a region

  • (more branches leads to less density)

what does a crosslink do to a polymer? what is the affect?

cross link (ionic, covalent, or hydrogen bonding) is a binder between polymer chains

• increase strength, rigidity (decrease flexibility), and melting point

plasticizer contain _____ which are added to _____ (improve/decrease) flexibility

phthalates, improve

when proteins are synthesized inside a cell, they exist as _____ (folded/unfolded)

unfolded

what causes proteins to fold in intramolecular interactions?

interactions between amino acid residues

what causes proteins to fold in intermolecular interactions?

interactions with water molecules

why do proteins fold?

they fold into the most structural conformation that is the most energetically stable in that enviornment

How would you expect this protein to fold if immersed in oil or water?

• oil: hydrophobic - the bottom side prefers oil (interactions that are primarily dispersion force IMF’s)

  • the protein will fold to expose the hydrophobic side chains to interact w the lipid tails (dispersion)

• water: hydrophilic - the top side prefers H2O; proximity for H-bonding and dipole-dipole IMFs

  • the protein will fold so that the hydrophobic (benzene rings, ect) are tucked into the inner core

define saturation and single vs double bond

refers to how many of the hydrocarbons are saturated (filled) with hydrogens

• saturated: contain only a single bond are are “saturated” with the maximum amount of hydrogen

• unsaturated: double or more bonds which means fewer hydrogen atoms

which is a trans or cis configuration?

cis (left, same side hydrogens) ; trans (right, different side hydrogens)

what are bonds and cis/trans related with fats?

• if there are more double bonds - there is less effective dispersion (causes bend and liquid at room temp)

• cis causes more bends in the chain so less effective dispersion IMF (h same side)

• trans keeps the chain straight (hydrogen on opposite sides) - tightly packed (artificial butter solid at room temp)