Changes of state of matter

What are the changes in the state of matter?

The changes of state of matter refer to the transformations that matter undergoes from one state to another without changing its composition. These changes occur when pressure and/or temperature variations.

On Earth, the solid, liquid, gaseous and plasmatic states are naturally manifested. The changes of state that occur between these are vaporization, fusion, solidification, sublimation, reverse sublimation, ionization, and deionization.

Let's see what they consist of, how they are produced, and what are the most common examples in daily life.

Solidification

Left: transition from the liquid state (water) to the solid-state (ice). Right: transition from melted chocolate to solid chocolate, on a tablet.

Solidification is the change from liquid to solid-state. It occurs when the temperature of a liquid or fluid drops significantly.

How does solidification occur? When the temperature of the fluid drops, the particles approach each other more and more until they are so compact that the movement between them is reduced. This approach and lack of mobility between the particles is what gives firmness to solids.

The maximum point at which the fluid hardens is known as the freezing point.

examples

1. Ice formation.
2. Chocolate hardening.
3. Hardening of molten metals (jewelry, work tools, etc.).
4. Manufacture of bar soaps.
5. Gelatin hardening.

melting

Left: transition from solid (ice) to liquid (water). Right: melting popsicles.

Fusion or melting is the change from the solid to the liquid state. Melting occurs when the solid is exposed to increased temperature.

How does melting or melting occur? When the temperature is raised considerably, the particles of solid matter begin to separate from each other. As the separation is greater, the particles gain more movement. Consequently, matter begins to gain a fluid aspect and loses its shape. That is, the solid turns into a liquid.

examples

1. Melting of the polar ice caps.
2. Melted chocolate.
3. Melted butter for cooking.
4. Melted candle wax (paraffin).
5. Melting of popsicle ice creams exposed to ambient heat.

Vaporization or evaporation

Left: transition from liquid to a gaseous state. Right: Pan of boiling water (in evaporation).

Vaporization is the change from liquid to a gaseous state. Vaporization occurs when a liquid is exposed to a rise in temperature.

How does vaporization occur? Vaporization is a process that proceeds steadily and slowly in certain fluids but speeds up when the liquid reaches the boiling point.

Under these conditions, the particles begin to move away from each other. The interaction between them is broken and, therefore, their movement becomes expansive, giving rise to the formation of the gaseous state.

examples

• Boiling water vapor.
• Drying of a damp floor.
• sweat evaporation
• Drying clothes in the open air.
• Formation of clouds by evaporation of terrestrial water.

 

Condensation

Left: transition from gaseous to a liquid state. Right: perspiration from a glass of ice water in a warm environment.

Condensation is the change from a gaseous to a liquid state. Condensation occurs when the temperature drops and/or the pressure rises in the environment.

How does condensation occur? When the temperature drops and/or the pressure rises, the particles that make up the gas begin to approach each other, so they lose part of their mobility. In this way, the change from gaseous to liquid state occurs.

examples

• The rain.
• Perspiration from a glass of cold liquid.
•  
• Fogging of glass and mirrors.

Sublimation

Left: transition from solid to gaseous state. Right: dry ice sublimation.

Sublimation is the direct change from the solid to the gaseous state. In this case, there is no passage through the liquid state. In fact, the word sublimation comes from the Latin sublimate, which means 'to rise'.

Sublimation occurs when a solid stored at an extremely low temperature comes into contact with a higher temperature, within a given pressure.

How does sublimation occur? For all substances, there is a point of temperature and pressure at which the solid, liquid, and gaseous states coexist in equilibrium, which is called the triple point.

When the temperature of the solid-state is below the triple point and, in addition, the vapor pressure is low enough, conditions for liquid formation do not exist. Then, any input of energy (heat), no matter how small, causes the particles of the solid to abruptly separate and expand in space as a gas.

For example, dry ice is a solid block of carbon dioxide (CO ₂ ) and is stored at a temperature of -78ºC, that is, below the triple point. When dry ice is exposed to room temperature, at a pressure lower than 5.2 atmospheres, it transforms into a gas directly. This is sublimation.

examples

• Dry ice sublimation.
• Naphthalene sublimation.
• dye sublimation
• Chemical sublimation for medicines.

Reverse sublimation or deposition

Left: transition from gaseous to solid-state. Right: snow deposits.

Reverse sublimation is the direct change from the gaseous to the solid-state. Reverse sublimation is also known as deposition, reverse sublimation, backward sublimation, desublimation, or crystallization.

Reverse deposition or sublimation occurs when the gas comes into contact with very low temperatures quickly or suddenly.

How does reverse sublimation or deposition occur? When a gas or vapor is exposed to very low temperatures and under certain humidity conditions, it loses its heat energy rapidly. Thus, its particles are compacted, and it passes into the solid-state.

examples

•  
• Frost formation.
• Aircraft contrails in the sky.
• Soot formation in chimneys.

ionization

Left: transition from gaseous to plasmatic state. Right: lightning in a thunderstorm.

Ionization is the change of gas to plasma. This process takes place when a gas is heated.

How does ionization occur? When a gas is heated, the particles that make up the gas begin to move faster and collide with each other. This increases the energy level, causing the outermost electrons of the atoms to be lost and the atom to become an ion.

Part of the energy of these atoms and electrons can give rise to photons. This process causes the gas to glow, which gives rise to plasma.

examples

• Lightning from thunderstorms.
• The polar lights (northern lights and aurora australis).
• Neon lights.
• Plasma televisions.
• Plasma lamps.

Deionization

Left: change from plasma to gaseous state. Right: metal welding process.

Ionization is the change of gas to plasma. It is the reverse process of ionization. It occurs when an electrically charged gas cools.

How does ionization occur? Contrary to ionization, deionization is a process in which a gas is cooled, causing it to lose its energetic charge.

Example.

• The smoke is generated during the metal welding process.
• The smoke of a recently extinguished flame.

 

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