1.5 Flashcards
true or false: without intermolecular forces of attraction between particles, all particles will move independently and be gases
true
What does condensed phases mean?
liquids and solids
true or false: solid and liquid has similar densities
true, also they are both much denser than gas
Describe condensed phases
- similar densities: particles are extremely close
- particles no longer have enough KE to overcome intermolecular attractions
- this is due to attraction between opposite charges
What is the physical state of a substance due to?
a balance between:
- average kinetic energy of particles
- potential energy of intermolecular attractions between particles
what is the type of intermolecular forces present depend on?
depends on the type of molecule
Briefly describe liquid physical properties
fluid
have surface properties
when pressure is applied to it, it is transmitted equally in all directions
What are intermolecular forces? Where do they occur?
- collectively known as Van der Waals forces
- they create structure in condensed phases
- generally weak; occur BETWEEN molecules
When you boil a substance what do you break?
No, not the strong covalent bonding; which occurs WITHIN molecules, but rather the weak intermolecular forces which occur BETWEEN molecules
true of false: every molecule is attracted to its neighbor
true
Why do these van der waals forces occur?
It is due to the uneven distribution of electrons due to geometry of each molecule
Describe ion- dipole forces
ion and polar molecule attract strongly to each other
Describe dipole- dipole forces
attractions occur between oppositely charged poles on polar molecules
- depends on the orientation being correct
true or false: the hydration of ion is always exothermic
true
true or false: higher charge density (relative to its size) = more negative change in hydration enthalpy (delta H hydration)?
true
Does the difference between lattice energy and hydration energy determine if dissolving is either exothermic/ endothermic
yes
what is lattice energy?
lattice energy of an ionic solid is a measure of the strength of bonds in that ionic compound
What is hydration energy?
comparing ions surrounded by water
What are dispersion (london) forces? a.k.a instantaneous dipole- induced dipole forces
- occur in ALL molecular substances and GROUP 18 (noble gases)
- momentary distortion (polarization) of electron clouds results in temporary dipole
- causes induced dipole in neighbor and attraction between dipoles in adjacent molecules (need to be very close)
(electron cloud not symmetrical anymore; weak intermolecular attraction occurs)
true or false: the boiling point increases with increasing dipole moment for molecules with similar number of electrons
true
What does the Dispersion (london) forces depend on?
The relative strength depends on SIZE and SHAPE of electron cloud surrounding molecule
eg. large proton; more electrons; thus increases the likelihood of polarisation
true or false: the melting points and boiling points increase as total number of electrons increase
true; this is a reflection of increasing attractions between these molecules
does the arrangement of the molecules influence the strength of their attraction with each other?
yes, increasing surface area of contact increases strength of intermolecular attraction
true or false, with similar dispersion forces higher boiling points occur for more polar molecules
true
What is hydrogen bonding?
- type of dipole- dipole force
- occurs when H (bonded to N,O,F) is attracted to lone electron pair of N,O,F on another molecule
- it is the dominant intermolecular force for H2O, NH3 and HF
- needs a lone pair of electrons
