Permanent dipole - dipole forces and Induced Dipole-Dipole Forces

Question 1

What kind of dipoles do polar molecules have

Answer 1

permanent dipoles

The molecule will always have a negatively and positively charged end

Question 2

Forces between two molecules that have permanent dipoles are called?

The δ+ end of the dipole in one molecule and the…………….. in a neighbouring molecule are attracted towards each other

Answer 2

permanent dipole - dipole forces

δ- end of the dipole

Question 3

Induced dipole - dipole forces exist between

Answer 3

all atoms or molecules

Question 4

Induced dipole-dipole forces are also called

Answer 4

van der Waals forces or London dispersion forces

Question 5

WATCH VID TO UNDERSTAND BETTER

Question 6

The electron charge cloud in non-polar molecules or atoms are?

Answer 6

constantly moving

During this movement, the electron charge cloud can be more on one side of the atom or molecule than the other

Question 7

During this movement, the electron charge cloud can be more on one side of the atom or molecule than the other this causes a ……… to arise

Answer 7

This causes a temporary dipole to arise

Question 8

When a temporary dipole arises the δ+ end of the dipole in one molecule and the δ- end of the dipole in a neighbouring molecule are attracted towards each other

Because the electron clouds are moving constantly, the dipoles are only …….

Answer 8

temporary

Question 9

For small molecules with the same number of electrons what forces are stronger permanent or induced ?

Answer 9

Pd-pd forces are stronger than id-id forces in smaller molecules with an equal number of electrons

Butane and propanone have the same number of electrons

Butane is a nonpolar molecule and will have induced dipole forces

Propanone is a polar molecule and will have permanent dipole forces

Therefore, more energy is required to break the intermolecular forces between propanone molecules than between butane molecules

So, propanone has a higher boiling point than butane

Question 10

Exam Tip

Remember: Intramolecular forces are forces within a molecule, whereas intermolecular forces are forces between a molecule.