What is true about intermolecular forces?
Select the correct answer below:
A. They are attractions within a molecule.
B. They are attractions between molecules or particles.
C. They are stronger than bonds between atoms.
D. They only occur in the gas phase.
The Correct Answer and Explanation is:
Correct Answer: B. They are attractions between molecules or particles.
Explanation:
Intermolecular forces (IMFs) are the forces of attraction or repulsion that act between neighboring particles (atoms, molecules, or ions). They are distinct from intramolecular forces, which are the chemical bonds (such as covalent or ionic bonds) that hold atoms together within a molecule. That’s why option A is incorrect—IMFs occur between, not within, molecules.
Intermolecular forces play a key role in determining the physical properties of substances, such as boiling point, melting point, vapor pressure, and solubility. Common types of IMFs include:
- London dispersion forces: Present in all molecules, especially significant in nonpolar substances. These are the weakest IMFs, caused by temporary shifts in electron density.
- Dipole-dipole interactions: Occur between polar molecules, where the positive end of one molecule is attracted to the negative end of another.
- Hydrogen bonding: A particularly strong type of dipole-dipole interaction that occurs when hydrogen is bonded to a highly electronegative atom like nitrogen, oxygen, or fluorine.
- Ion-dipole forces: Occur between ions and polar molecules, especially important in solutions of ionic compounds in polar solvents like water.
Option C is incorrect because intermolecular forces are generally much weaker than the covalent or ionic bonds that hold atoms together in molecules. For example, breaking covalent bonds requires significantly more energy than overcoming IMFs.
Option D is also incorrect. Intermolecular forces exist in all phases of matter, not just the gas phase. In fact, they are particularly significant in liquids and solids, where molecules are close together and IMFs hold them in a condensed phase.
In summary, intermolecular forces are attractions between molecules or particles, and while weaker than intramolecular bonds, they are crucial in explaining many observable physical properties of matter.
