Which one among the following statements about matter is NOT correct ?

On increasing the temperature of solids, the kinetic energy of particles increases

The maximum temperature at which a solid melts to become a liquid at atmospheric pressure is called its melting point

Particles of steam have more energy than water at 100°C

Direct change of gas to solid is called deposition

This question was previously asked in

UPSC CAPF – 2024

Let’s examine each statement:
A) On increasing the temperature of solids, the kinetic energy of particles increases. This is correct. Temperature is a measure of the average kinetic energy of the particles.
B) The maximum temperature at which a solid melts to become a liquid at atmospheric pressure is called its melting point. For a pure crystalline solid at constant pressure, melting occurs *at* a specific temperature called the melting point. Saying it is the *maximum* temperature at which it melts is imprecise or incorrect. Above the melting point, the substance is in the liquid state. For impure or amorphous solids, melting can occur over a range of temperatures, but the term ‘melting point’ usually refers to the start of the melting range or the specific temperature for pure substances. The phrasing “maximum temperature at which a solid melts” is misleading for a pure substance and not a standard definition for the melting point.
C) Particles of steam have more energy than water at 100°C. This is correct. When water boils at 100°C, it absorbs latent heat of vaporization to change state into steam at the same temperature. This latent heat increases the internal energy (primarily potential energy related to intermolecular forces) of the particles in the gaseous state compared to the liquid state at the same temperature.
D) Direct change of gas to solid is called deposition. This is correct. The phase transition from gas directly to solid is known as deposition or desublimation. The reverse process, solid to gas, is called sublimation.
Therefore, statement B is the incorrect statement due to its inaccurate phrasing regarding the melting point of a solid.

Understanding the states of matter, phase transitions, and the relationship between temperature, energy, and particle motion. Melting point is the specific temperature at which a pure crystalline solid melts at a given pressure.

Phase transitions like melting, boiling, sublimation, condensation, freezing, and deposition occur at specific temperatures (at constant pressure) for pure substances, involving the absorption or release of latent heat. The kinetic energy of particles is related to temperature within a single phase, while potential energy changes significantly during phase transitions.

More similar MCQ questions for Exam preparation:-