Question

Why is there no change in intramolecular forces when a solid is melted? Are intramolecular forces stronger or weaker than intermolecular forces?

Short answer

When a solid melts, intramolecular forces remain unchanged because melting affects only the arrangement and movement of molecules, not the molecular structure. Intramolecular forces, such as covalent and ionic bonds, are generally stronger than intermolecular forces, like dipole-dipole interactions and van der Waals forces. This difference in strength explains why most substances have relatively low melting points, as weaker intermolecular forces can be more easily overcome by heat.

Step-by-step solution

Define intramolecular and intermolecular forces

Intramolecular forces are the forces that hold atoms together within a molecule. These forces include covalent bonds, ionic bonds, and metallic bonds. Intermolecular forces, on the other hand, are the forces that exist between molecules, rather than within them. These forces include dipole-dipole forces, hydrogen bonding, and London dispersion forces (also called van der Waals forces).

Explain the melting process

Melting is the process where a solid substance turns into a liquid upon heating. During this process, the temperature of the substance increases, which causes an increase in the kinetic energy of its molecules. As a result, the molecules move faster and further apart from each other, leading to a change in the substance's physical state from solid to liquid. However, during melting, the molecules themselves do not break apart; they simply move more freely within the liquid.

Intramolecular forces during melting

When a solid melts, the intramolecular forces that hold the atoms together within the molecules remain unchanged. This is because the process of melting only affects the arrangement and movement of the molecules, not the structure of the molecules themselves. Therefore, covalent bonds, ionic bonds, and metallic bonds within the molecules remain intact during melting.

Compare the strength of intramolecular and intermolecular forces

In general, intramolecular forces are stronger than intermolecular forces. This is because intramolecular forces, such as covalent and ionic bonds, involve the sharing or transfer of electrons between atoms, which create strong attraction. Intermolecular forces, on the other hand, involve weaker attraction between molecules, such as through dipole-dipole interactions or van der Waals forces. This difference in strength is one of the reasons why most substances have relatively low melting points – the weaker intermolecular forces can be more easily overcome by heat, while the stronger intramolecular forces remain unaffected. In conclusion, there is no change in intramolecular forces when a solid melts because the process of melting affects the movement and arrangement of molecules, not the bonds within the molecules. Intramolecular forces are generally stronger than intermolecular forces due to the stronger attraction created by covalent and ionic bonds versus the weaker attraction of intermolecular forces.