A Level Chemistry OCR Practice Exam

What are van der Waals' forces?

1. Very strong forces between atoms in a molecule

2. Weak attractive forces between induced dipoles in neighboring molecules

3. Electrostatic forces between charged particles

4. Forces that occur only in ionic compounds

The correct answer is: Weak attractive forces between induced dipoles in neighboring molecules

The correct answer highlights that van der Waals' forces are indeed weak attractive forces that occur between induced dipoles in neighboring molecules. These forces result from temporary shifts in electron density that create instantaneous dipoles, which can then induce dipoles in adjacent molecules. This interaction leads to an attractive force between them, contributing to properties such as boiling and melting points in molecular substances. The other options do not accurately describe van der Waals' forces. For instance, the strongest forces in a molecule usually involve covalent or ionic bonds rather than the weak interactions characteristic of van der Waals' forces. Additionally, while electrostatic forces are a fundamental aspect of ionic bonding and interactions between charged particles, they are distinct from van der Waals' forces, which are non-covalent and weaker. Lastly, it is incorrect to state that such forces occur only in ionic compounds, as van der Waals' forces can be found in all types of molecular interactions, including polar and nonpolar substances.