Ch 10 Ppt
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In terms of distance, what are gases? They have what?
We can do what to form a __.
Compared to solids, they are __. Why is this?
- far apart
- elastic energy
- compress them to form a liquid
- not as rigid as solids
- solids can't flow
What are intermoleuclar forces?
attractions between "molecules" that hold them together
What are intramolecular forces?
forces holding together particles, such as polar covaluent bonds
__ form between atoms of different __. This is described as a __, one type of __ force.
- polar covalent bonds
- bond dipole
- intramolecular force
What is a dipole moment?
- the measure of net molecular polarity or charge separation
- u= Q ' r
- r= distance between charges
Dipole moments are expressed in __.
Polarity can be illustrated with an __.
electrostatic potential map
What do electrostatic potential maps show?
electron-rich groups as red and electron-ppor groups as blue-green
The greater the charge, the __ the dipole moment.
If you have a non-polar moment, will it have a dipole moment?
What is the minimum requirement of a diploe moment?
- must have a polar attraction
If arranged asymmetrically, what happens with the dipole moment?
What is it called? Where does it occur?
- they will not cancel each other out
- net dipole moment
- toward lone pair
The individual bond polarities do not cancel. Therefore, the molecule has a __. In other words, the molecule is __.
The individual bond polarities cancel. Therefore, the molecule does not have a __. In other words the molecule is __.
What are intermolecular forces?
- attractions between "molecules" that hold them together
- much weaker than intramolecular forces
Types of intermolecular forces?
- ion-dipole forces
- van der waals forces: dipole-dipole forces; London dispersion forces; hydrogen bonds
the result of electrical interactions between an ion and the partial charges on a polar molecule
result of electrical interactions among dipoles on neighboring moleucles
Do you get a complete charge with a dipole species?
Melting point of ion-dipole?
higher due to stronger forces
The higher the molecular weight, the more likely what?
it'd become a solid
As the dipole moment incresaes, what?
the intermolecular forces increases
As the intermolecular forces increase, what happens?
the boiling point incresaes
London Dispersion Forces
the result of the motion of electrons which gives the molecule a short-lived dipole moment. This induces temporary dipoles in neighboring molecules
There may be instances where both electrons are at one part of the molecule instead of shared. This is called __
instantaneous dipoles; they are not fixed
The bigger hte molecule is, what?
the more likely this is to occur (the instataneous dipoles)
an attractive force between a H atom bonded to very electronegative atom and an unshared electron pair on another electronegative atom
Hydrogen bonds are (stronger/ weaker) than ordinary attractions.
What characteristics does hydrogen bonding give to water?
- higher melting point
- solidifying causes it to expand; ice is less dense
- huge temp. changes in desert due to no H2O available since water is a great absorber of heat
Strength of covalent bond weaker than hydrogen.
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