Intermolecular forces and metallic bonding
Watch the whole lecture free
Make a free account to watch every lecture to the end: 2 practice questions, 5 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
That was the teaching part. The rest of this lecture is free with an account: 2 practice questions, 5 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
No password needed now: we email you a link to set one. Already have an account? Sign in, then come back to this page.
The teaching part (1 min) is free to watch. A free account opens the whole lecture: 2 practice questions, 5 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Why ice floats and lizards climb walls
- Three types of intermolecular force
- Instantaneous dipole-induced dipole forces
Read the transcript of the teaching part
Last time
Before we start: last time, in Hybridisation, sigma and pi bonds, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Why ice floats and lizards climb walls
Ice floats on water, which is strange for a solid. And a gecko walks up a smooth glass wall without glue. Both come from forces between molecules, which are much weaker than the covalent bonds inside them, but not negligible.
Three types of intermolecular force
Instantaneous dipole-induced dipole forces, also called London dispersion forces, act between all molecules. They are the weakest. Permanent dipole-permanent dipole forces act between polar molecules. Hydrogen bonds act when hydrogen is bonded to nitrogen, oxygen or fluorine. They are the strongest of the three. All of them are far weaker than covalent bonds.
Instantaneous dipole-induced dipole forces
Electrons move constantly, so at any instant the electron cloud may be uneven, giving a temporary dipole. This dipole induces a dipole in a neighbouring molecule, and the two attract. The more electrons in a molecule, the larger and more polarisable its cloud, and the stronger the force. A larger surface area also increases contact, so a straight chain has a higher boiling point than a branched isomer.
Chapter 3: Chemical bonding
- Covalent bonding, shapes and electronegativity 7 min
- Hybridisation, sigma and pi bonds 7 min
- Intermolecular forces and metallic bonding 7 min
Also for A Level Chemistry 9701
Which topics come up most in A Level Chemistry 9701 past papers, counted from every paper since 2004: Paper 2 topic frequency, Paper 4 topic frequency.