Short Answer

Freezing or solidification is the process in which a liquid changes into a solid when heat is removed. When a liquid is cooled, its particles lose energy and move more slowly. As a result, the particles come closer and get fixed in definite positions, forming a solid. Every liquid has a specific temperature at which it freezes, called the freezing point.

A common example of freezing is water turning into ice when kept in a freezer. Freezing is a reversible physical change because a solid can melt back into a liquid when heated again.

Detailed Explanation :

Freezing or Solidification

Freezing, also known as solidification, is a physical process where a liquid becomes a solid when heat is removed. This change happens because cooling reduces the movement of particles, allowing them to come closer and arrange themselves in a fixed structure. In the solid state, particles remain tightly packed, and the substance gains a definite shape and volume. Freezing is an important part of the interconversion of states of matter and is seen commonly in daily life.

During freezing, the temperature of the liquid drops until it reaches its freezing point. At this temperature, the liquid begins to turn into a solid. The freezing point of water is 0°C, but different liquids have different freezing points. For example, coconut oil solidifies in winter at a much higher temperature than water.

Freezing does not create a new substance. It only changes the physical form. For instance, water (liquid) and ice (solid) are both made of H₂O molecules.

How Freezing Happens

1. Removal of Heat Energy

Freezing begins when heat is removed from a liquid. The liquid loses thermal energy, which reduces the speed of its particles. When particles lose energy, they move slowly and cannot slide freely as they did in the liquid state.

During cooling:

• Particles lose kinetic energy.
• Movement slows down.
• Temperature drops steadily.

This reduction in energy prepares the particles for the solid state.

2. Decrease in Particle Movement

In a liquid, particles move freely and slide over one another. However, when the liquid cools:

• Particle vibration becomes weaker.
• Particles start clustering together.
• They cannot move far from their positions.

This change causes the liquid to become thicker and eventually turn into a solid.

3. Increase in Intermolecular Attraction

As particles lose heat and move slowly, the forces of attraction between them become stronger. Stronger attraction pulls particles closer, making them settle into fixed positions.

Effects of stronger attraction:

• A stable solid structure forms.
• Particles get arranged in an orderly pattern.
• The liquid loses its ability to flow.

This marks the beginning of the solidification stage.

4. Freezing Point

The temperature at which a liquid changes into a solid is called its freezing point. At this temperature:

• The liquid begins to solidify.
• Heat energy removed is used to change the state, not to decrease the temperature further.
• The temperature remains constant until the entire liquid becomes solid.

Examples of freezing points:

• Water freezes at 0°C.
• Pure silver freezes at 961°C.
• Coconut oil may freeze around 24°C (depending on purity).

5. Formation of a Solid

Once the particles settle into fixed positions, the liquid becomes a solid. Solids have:

• A fixed shape
• A fixed volume
• Low particle movement
• Strong intermolecular forces

These changes explain why frozen substances become hard and cannot flow.

Examples of Freezing in Daily Life

Freezing is a common process that we observe in many activities:

• Water turning into ice in a freezer
• Ice cream becoming solid after cooling
• Molten metal solidifying in molds during metalwork
• Wax turning solid after a candle is extinguished
• Coconut oil becoming solid during winter

These examples show how liquids become solid when heat is removed.

Freezing as a Physical Change

Freezing is considered a physical change because:

• The chemical composition remains the same.
• Only the state of matter changes.
• It is reversible (solid → liquid on heating).

For example, when ice melts, it returns to liquid water without forming a new substance.

Conclusion

Freezing or solidification is the process in which a liquid becomes a solid by losing heat. When particles lose energy, they move slowly, come closer, and arrange themselves in fixed positions. This process occurs at a specific temperature known as the freezing point. Freezing is a physical and reversible change that plays an important role in nature and everyday life, from making ice to shaping metals.