lecture 4.1 – intermolecular forces and the dissolving process
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Lecture 4.1 – Intermolecular Forces and the Dissolving Process. Today ’ s Learning Targets. LT 4.1 – I can discuss how ionic solids dissolve due to the random molecular motion of the water molecules. - PowerPoint PPT PresentationTRANSCRIPT
Today’s Learning Targets• LT 4.1 – I can discuss how ionic solids dissolve due to the
random molecular motion of the water molecules. • LT 4.2 – I can identify a compound as containing
hydrogen bonding, dipole – dipole forces, and Van der Waals forces.
• LT 4.3 – I can compare and contrast various intermolecular forces and relate them to the dissolving process of a solid.
I. Intermolecular Forces• Intermolecular forces are forces that attract molecules
to one another. • The three main types of intermolecular forces are:
(1) Hydrogen Bonding(2) Dipole-Dipole Forces(3) Dispersion Force (also known as Van der Waals
Forces)
H F
FH
Pulls electrons towards itself because it has a higher electronegativity
Partial negative charge
δ-δ+
This is what a dipole looks like
III. Dipole-Dipole Forces• Dipole-dipole forces refer to the attraction
between molecules that have a permanent dipole.
III. Dispersion Forces• Some molecules have an induced dipole. • Dispersion forces are the intermolecular
forces resulting from the uneven distribution of electrons and the creation of temporary dipoles.
• Weakest intermolecular force
There is no electronegativity difference between two hydrogens, so they are non-polar and do not have a dipole
But, when two H2 molecules are put next to one another, a dipole is induced because electrons rearrange themselves
IV. Hydrogen Bonding• Hydrogen bonding is the attraction of one molecule
that contains hydrogen to another molecule. • When hydrogen is bound to N, O, or F, there is a large
difference in electronegativity • Creates a partial positive and negative charge• The partial positive charge on hydrogen is attracted
to N, O, or F of another molecule.
V. Intermolecular Forces and Phase of Substance
• The degree of intermolecular forces determines the phase of a substance.
Least intermolecular forces
Most intermolecular forces