MCQ Detailed View

The process in which a substance changes from a liquid state to a solid state is called freezing. This physical change occurs when the temperature of a liquid is lowered to or below its freezing point, causing the particles to lose energy and arrange themselves into a fixed, rigid structure. For water, this freezing point is 0°C (32°F) at normal atmospheric pressure.

Freezing is an example of a phase change or change of state of matter. In the liquid state, molecules have enough energy to move around each other freely. When heat is removed, their kinetic energy decreases, and intermolecular forces become stronger, pulling the particles into a stable, organized lattice, which is the solid state. This transition is a physical change because the chemical composition of the substance remains the same. For example, water (H₂O) remains water whether in liquid or solid form; only its physical state changes.

It is important to distinguish freezing from other processes:

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  Boiling is the change of state from liquid to gas.

  
  


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  Evaporation is also a liquid-to-gas change, but it happens at the surface and below boiling temperature.

  
  


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  Condensation is gas changing into liquid.

  
  

Freezing is widely observed in everyday life. Examples include water turning into ice in a freezer, molten lava cooling to form solid rock, or liquid metals solidifying when cooled. This process also plays a critical role in nature. The freezing of lakes, the formation of snow and ice, and the preservation of food all depend on this phase change.

From a Physics perspective, freezing demonstrates the role of thermal energy, molecular motion, and intermolecular forces in determining the state of matter. Understanding freezing helps students grasp broader concepts of thermodynamics, heat transfer, and matter behavior.

Thus, the correct answer is Freezing.