6.3 : Intermolecular Forces Flashcards Preview

Chemistry Module 2 > 6.3 : Intermolecular Forces > Flashcards

Flashcards in 6.3 : Intermolecular Forces Deck (16):

What are the three different types of intermolecular forces?

Induced dipole - dipole interactions ( London forces )

Permanent dipole - dipole interactions

Hydrogen bonding


Define intermolecular forces

Weak interactions between dipoles of different molecules


Order the intermolecular forces from strongest to weakest

( covalent )
Hydrogen bonds
Permanent dipole dipole
London forces


Describe how induced dipole - dipole interactions occur

Movement of electrons produces a changing dipole in a molecule

At any instant, an instantaneous dipole will exist, but it’s position is constantly shifting

The instantaneous dipole induces a dipole on a neighbouring molecule

The induced dipole induces further dipoles on neighbouring molecules, which then attract one another.


What is another name for induced dipole - dipole interactions ?

London forces


Are London forces permanent or temporary?



How do you increase the strength of London forces?

The more electrons in each molecules
The larger the instantaneous and induced dipoles
The greater the induced dipole - dipole interactions
The stronger the attractive forces between molecules


What are permanent dipole dipole interactions ?

They act between the permanent dipoles in different polar molecules.


How does have permanent dipole dipole interactions affect boiling point? Give an example with fluorine and HCl

F = non polar, only London forces
HCL = polar, have London forces and permanent dipole dipole interactions

Extra energy required to break the additional permanent dipole dipole interactions

Boiling point of HCL is higher than F2


What a simple molecular lattice?

The molecules are held in place by weak intermolecular forces

The atoms within each molecule are bonded together strongly by covalent bonds

They are formed from simple molecules


Describe and explain the boiling and melting points of simple molecular substances

The weak intermolecular forces of a simple molecular lattice can be broken even by the energy present at low temperatures.

Therefore, they have low melting and boiling points.


What happens when a simple molecular substance is melted?

Only the weak intermolecular forces break

The covalent bonds are strong and do not break


Describe and explain the solubility of non - polar simple molecular substances

When it is added to a non polar solvent, imf’s form between the molecules and solvent.

The interactions weaken the imfs in the simple molecular lattice. The imfs break and the compound dissolves.

When it is added to a polar solvent, there is little interaction between the molecules in the lattice and the solvent molecules.

The intermolecular bonding within the polar solvent is too strong to be broken.


Summarise the solubility of non polar simple molecular substances

Not soluble in polar solvents
Soluble in non polar solvents


Describe and explain the solubility of polar simple molecular substances

They may dissolve in polar solvents as the polar solute molecules and the polar solvent molecules can attach each other.

The solubility depends on the strength of the dipole and can be hard to predict.


Describe and explain the electrical conductivity of simple molecular substances

There are no mobile charge particles in simple molecular structures.

Within no charged particles that can move, there is nothing to complete an electrical circuit.

Simple molecular structure = non - conductor