Questions and Answers
What are intramolecular forces?
Interaction between atoms within a molecule.
What are intermolecular forces?
Interactions between molecules/atoms.
Which are stronger, intermolecular forces or intramolecular forces?
Intramolecular forces are stronger.
What influences water's physical properties (including its boiling point and melting point)?
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How do the attractive forces of a molecule influence its physical properties?
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What is the relationship between energy required to separate particles and boiling point?
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What is an induced dipole?
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Why are the partial charges in temporary dipoles in molecules more likely to be distributed over greater distances than in single atoms?
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What is lattice energy?
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Larger lattice energies typically correspond to what?
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What is a dispersion force?
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Why do the strength of dispersion forces increase as the number of electrons in atoms and molecules increase?
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What is polarizability?
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Why do larger molecules have higher boiling points?
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What are ion-dipole interactions?
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Why can a salt such as NaCl dissolve in water?
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Study Notes
Intermolecular and Intramolecular Forces
- Intramolecular forces refer to interactions within a molecule between its atoms.
- Intermolecular forces are interactions that occur between different molecules or atoms.
- Intramolecular forces are significantly stronger (100-1000 kJ/mol) compared to intermolecular forces (1-100 kJ/mol).
Properties of Water
- Water's unique physical properties, such as its boiling and melting points, are influenced by its polarity.
- Strong attractive forces in solids require more energy to overcome, resulting in higher melting and boiling points, indicating solidity at room temperature.
- Substances with weaker interactions tend to be liquids, while those with very weak interactions are likely gases.
Boiling Point and Energy
- Higher energies required to separate particles correlate with higher boiling points.
Dipoles and Interactions
- An induced dipole results from temporary uneven electron distribution in atoms or molecules, leading to charge separation.
- Temporary dipoles can extend further in molecules due to interactions between atomic nuclei and shared electron clouds.
Lattice Energy
- Lattice energy represents the energy needed to separate ions in an ionic solid. Larger (more negative) lattice energy indicates stronger ionic interactions.
- High melting points in ionic compounds are typically associated with larger lattice energies.
Dispersion Forces
- Dispersion forces are intermolecular forces that act between nonpolar molecules, driven by temporary dipoles.
- All atoms and molecules experience London dispersion forces; larger electron clouds lead to easier polarization and stronger intermolecular interactions.
- Increased polarizability results in stronger temporary dipoles and hence stronger dispersion forces.
Molecular Size and Boiling Points
- Larger molecules possess more surface area, increasing the likelihood of interactions through dispersion forces, leading to higher boiling points.
Ion-Dipole Interactions
- Ion-dipole interactions occur between an ion and a molecule with a permanent dipole, representing another form of intermolecular force.
Dissolution of Salt in Water
- The ability of salts like NaCl to dissolve in water is due to ion-dipole interactions overcoming the electrostatic forces holding the ions together.
- When dissolved, the ions become surrounded by water molecules, forming a hydration sphere.
Sphere of Hydration
- Water molecules in the hydration sphere orient based on the charge of the ion; oxygen atoms face cations and hydrogen atoms face anions, with the extent of orientation depending on the size of the ion.
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Description
Test your understanding of intermolecular and intramolecular forces with this set of flashcards from Chemistry Chapter 10. Learn key definitions and concepts that highlight the strengths and differences between these types of forces, particularly in relation to the unique properties of water.