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Questions and Answers
Which type of intermolecular force is considered the strongest?
Which type of intermolecular force is considered the strongest?
London Dispersion Forces are present only in polar molecules.
London Dispersion Forces are present only in polar molecules.
False
What effect do stronger intermolecular forces have on boiling and melting points?
What effect do stronger intermolecular forces have on boiling and melting points?
They increase boiling and melting points.
The measure of a fluid's resistance to flow is called __________.
The measure of a fluid's resistance to flow is called __________.
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Match the type of intermolecular force to its description:
Match the type of intermolecular force to its description:
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Study Notes
Intermolecular Forces
- Intermolecular forces are attractive forces between molecules.
- These forces influence properties like boiling/melting points, surface tension, and viscosity.
Types of Intermolecular Forces
London Dispersion Forces (Van der Waals Forces)
- Present in all molecules.
- Caused by temporary fluctuations in electron distribution, creating temporary dipoles.
- Strength increases with molecular size and surface area.
Dipole-Dipole Forces
- Occur between polar molecules.
- Result from the attraction between a positive end of one molecule and the negative end of another.
- Stronger than London dispersion forces, but weaker than hydrogen bonds.
Hydrogen Bonding
- A special type of dipole-dipole force.
- Occurs between a hydrogen atom bonded to a highly electronegative atom (N, O, or F) and a lone pair of electrons on another electronegative atom.
- The strongest of the intermolecular forces.
Intermolecular Forces and Physical Properties
- Boiling Point and Melting Point: Stronger intermolecular forces lead to higher boiling and melting points as more energy is required to overcome these attractive forces between molecules.
- Surface Tension: Intermolecular forces cause liquids to have a high surface tension, where the surface contracts. Liquids with stronger intermolecular forces have higher surface tension.
- Viscosity: Viscosity is a liquid's resistance to flow. Liquids with stronger intermolecular forces have higher viscosity.
Summary Table
| Intermolecular Force | Description | Strength | Example |
|---|---|---|---|
| London Dispersion Forces | Temporary dipoles | Weakest | All molecules |
| Dipole-Dipole Forces | Attraction between polar molecules | Moderate | HCl, HBr |
| Hydrogen Bonding | Strong dipole-dipole force involving H and N, O, or F | Strongest | H₂O, NH₃, HF |
Key Points
- Intermolecular forces are weaker than intramolecular forces (bonds within molecules).
- The strength of intermolecular forces affects the physical properties of substances.
- Understanding intermolecular forces helps explain phenomena like evaporation, condensation, and the behavior of liquids and solids.
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Description
Explore the fascinating world of intermolecular forces including London dispersion forces, dipole-dipole interactions, and hydrogen bonding. Understand how these forces affect the physical properties of substances like boiling points and viscosity. This quiz will test your knowledge of these essential concepts in chemistry.
