Interconversion of Matter: Sublimation, Solidification, Melting

You have landed on the right page to learn about Interconversion of Matter. We have already studied that matter can exist in three physical states: solid-state, liquid state, and gaseous state or vapour state. We should remember that solid, liquid, and gas are not substances but are three states of the same substance which differ in interparticle spaces. For example, water exists as a solid in the form of ice, as a liquid in the form of water, and gas in the form of steam.

Do you believe the three states can be switched out? Yes, you may switch between these three conditions. When we keep ice in a container, it begins to melt and turn into water. Water vapours are produced when this water is heated. Ice is a solid, water is a liquid, and water vapour is gas in this situation. The three states of matter differ in terms of interparticle spaces, as we have learned. In the gaseous state, interparticle space is greatest, while in the solid-state, it is smallest. Let us study the effect of pressure and temperature in the interconversion of states of matter.

Effect of Change of Temperature

Temperature is one of the most important factors in generating a change in the state of matter. The kinetic energy of solid substance constituent particles increases as it is heated. As a result, the particle begins to vibrate at a faster rate. This extra energy aids the particles in overcoming the attraction between them. They soon leave their places and begin to move morely. As a result, the components melt and turn into a liquid state.

It has been observed that temperature remains constant until all solids melt into a liquid. The heat supplied is used for changing the solid state into a liquid state by overcoming the interparticle attraction force. Thus, the solid substance absorbs heat energy without showing any rise in temperature.

Similarly, when the liquid substance is heated, the kinetic energy of its constituent particles increases, and due to this, the particles start vibrating with greater speed. This extra energy helps the particles to overcome the interparticle forces of attraction. Soon they start to move morely. Consequently, the liquid state gets converted into a gaseous state.

Change of State from Solid to Gas(Directly): Sublimation

Some of the solids, when heated, directly pass into the vapour phase without passing through the liquid state.

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When solid dry ice is exposed to air, it creates a layer of cold air that stays in place around it. This layer of cold air acts as an insulator that prevents further warm air from coming in contact with dry ice. The warm air will eventually leach away the layer of cold air, but much more slowly than if warm air were constantly in contact with dry ice. As a result, there are many layers of cold \({\rm{C}}{{\rm{O}}_{\rm{2}}}\left( {\rm{g}} \right)\) in a pool around the chunk of dry ice. Thus, the physical state of dry ice at \({\rm{20}}\,^\circ {\rm{C}}\) can be described as solid. We can even weigh it approximately at \({\rm{20}}\,^\circ {\rm{C}}.\)

Sublimation is defined as a process during which a solid on heating changes directly into the vapour phase without passing through the intermediate liquid state. When the vapours are cooled, they condense to form a solid.The examples of solids that undergo sublimation on heating are naphthalene, camphor, dry ice (solid \({\rm{C}}{{\rm{O}}_{\rm{2}}}\)), iodine, ammonium chloride, mercury \(\left( {{\rm{II}}} \right)\) chloride, etc.

Activity to Understand Sublimation

Let us perform an activity to understand the process of sublimation.

Take a mixture of sand and iodine in a china dish and cover it with a perforated asbestos sheet. Place an inverted glass funnel over the perforated asbestos sheet. Insert a cotton plug in the stem of the funnel. Heat the china dish slowly with a Bunsen burner and observe. Iodine passes into the vapour phase directly, and sand remains unaffected by heating. The violet iodine vapours condense on the cooler parts of the funnel to form dark, shiny crystals of iodine. The iodine thus obtained is called sublimate. Sublimate is the pure form of a compound. This activity is a method of separating a mixture of two solids, one of which sublimes.

Change of Solid State into the Liquid State: Melting

The material matter must be heated or cooled to effect the transformation. When we heat ice, it turns into water; the solid material becomes a liquid. Melting or fusion of ice is the term for this process. The melting of a solid substance occurs at a constant temperature. As a result, we can define melting as follows:

“The temperature at which a solid substance melts and changes into a liquid at atmospheric pressure is known as the melting point of the solid”.

Since ice melts at zero degrees Celsius, the melting point of ice is \({\rm{0}}\,^\circ {\rm{C}};\) that is, ice melts at the temperature of \({\rm{0}}\,^\circ {\rm{C}}\) and changes its state from solid to liquid. For ice, the latent heat of fusion is \(334\;{\rm{kJ}}\;{\rm{k}}{{\rm{g}}^{ – 1}}.\) Which means that \(334\;{\rm{kJ}}\) of heat is required to convert \({\rm{1}}\,{\rm{kg}}\) of ice at \({{\rm{0}}^{\rm{o}}}{\rm{C}}\) into \({\rm{1}}\,{\rm{kg}}\) of water at \({{\rm{0}}^{\rm{o}}}{\rm{C}}.\) Conversely, \(334\;{\rm{kJ}}\) of heat is released when one kg of waterzes at \({\rm{0}}\,^\circ {\rm{C}}\) to give one \({\rm{kg}}\) of ice at \({\rm{0}}\,^\circ {\rm{C}}.\)

However, different solids have different melting points. Thus, we can say that the melting point of a solid is a measure of the force of attraction between its particles. When the melting point of a substance is high, the force of attraction between its particles will be greater. For example, the melting point of iron is very high, and so the force of attraction between the particles of iron is very strong.

How Solid Changes into a Liquid on Heating?

Let us understand how a solid changes into a liquid on heating.

When a solid is heated, the heat energy makes the particle in it vibrate more vigorously. At the melting point, the particles in the solids have sufficient energy to overcome the strong force of attraction, holding the particles in fixed positions and so break them to form small group particles, thereby forming a liquid.

The heat energy absorbed by ice is the latent heat which is in the hidden form and is called the latent heat of fusion.

Latent Heat of Fusion or Melting

The process of conversion of a solid into a liquid form is called fusion. Hence, we can define latent heat of fusion as:

“The quantity of heat required to convert \(1\) unit of mass of solid into liquid at atmospheric pressure at its melting point without any change in the temperature is called the latent heat of fusion”.

In other words, ‘the amount of heat energy required to convert \({\rm{1}}\,{\rm{kg}}\) of a solid into a liquid at its melting point without any rise in temperature under atmospheric pressure.’

The SI unit of latent heat of fusion is joules per kilogram.

Latent Heat of Fusion of Ice

The quantity of heat energy required to change \({\rm{1}}\,{\rm{kg}}\) of ice into the water at atmospheric pressure at its melting point \(\left( {{\rm{0}}\,^\circ {\rm{C}}} \right)\) without any change of temperature is called the latent heat of the fusion of ice. The value of latent heat of fusion of ice is \(3.35 \times {10^5}\;{\rm{J}}\;{\rm{k}}{{\rm{g}}^{ – 1}}.\) 

Thus, the energy of \({\rm{1}}\,{\rm{kg}}\) of water at \({{{\rm{0}}^{\rm{o}}}{\rm{C}}}\) is \(3.35 \times {10^5}\;{\rm{J}}\) more than that of ice at the same temperature. In the process of fusion, \({\rm{1}}\,{\rm{kg}}\) of ice at \({{{\rm{0}}^{\rm{o}}}{\rm{C}}}\) can withdraw from the surroundings \(3.35 \times {10^5}\;{\rm{J}}\) more heat energy than \({\rm{1}}\,{\rm{kg}}\) of water at the same temperature \(\left( {{\rm{0}}\,^\circ {\rm{C}}} \right)\) could do. Hence, at \({\rm{0}}\,^\circ {\rm{C}},\) ice is more effective in cooling than the same quantity of water at the same temperature \(\left( {{\rm{0}}\,^\circ {\rm{C}}} \right).\)

Study About Classification of Matter Here

Change of Liquid state into Gaseous state: Boiling or Vaporization

Latent Heat of Vaporisation

The process of change of a liquid into vapour is called vaporization. The heat energy required to change \({\rm{1}}\,{\rm{kg}}\) of a liquid into vapour at atmospheric pressure at its boiling point without any change of temperature is called the latent heat of vaporization. The SI unit of latent heat of vaporization is \({\rm{J}}\;{\rm{k}}{{\rm{g}}^{ – 1}}.\)

Latent Heat of Vaporization of water

Latent heat of vaporization of water is the amount of heat energy required to change \({\rm{1}}\,{\rm{kg}}\) of water into vapour at atmospheric pressure at the boiling point of water without any change of temperature. The value of latent heat of vaporization of water is \(22.6 \times {10^5}\;{\rm{J}}\;{\rm{k}}{{\rm{g}}^{ – 1}}.\) Thus, the energy of \({\rm{1}}\,{\rm{kg}}\) of steam at \({{\rm{10}}{{\rm{0}}^{\rm{o}}}{\rm{C}}}\) is \(22.6 \times {10^5}\;{\rm{J}}\) more than that of water at the same temperature \(\left( {{\rm{100}}\,^\circ {\rm{C}}} \right).\)

This means that steam at \({{\rm{10}}{{\rm{0}}^{\rm{o}}}{\rm{C}}}\) is a more effective heating agent than water at the same temperature \(\left( {{\rm{10}}{{\rm{0}}^{\rm{o}}}{\rm{C}}} \right).\) It also means that when \({\rm{1}}\,{\rm{kg}}\) of steam at \({{\rm{10}}{{\rm{0}}^{\rm{o}}}{\rm{C}}}\) is condensed to \({\rm{1}}\,{\rm{kg}}\) of water at \({{\rm{10}}{{\rm{0}}^{\rm{o}}}{\rm{C,}}}\) heat energy equal to \(22.6 \times {10^5}\;{\rm{J}}\) is given out. The latent heat of vaporization of ethanol, diethyl ether, and mercury is \(8.5 \times {10^5}\;{\rm{J}}\;{\rm{k}}{{\rm{g}}^{ – 1}},3.9 \times {10^5}\;{\rm{J}}\;{\rm{k}}{{\rm{g}}^{ – 1}}\) and \(2.8 \times {10^5}\;{\rm{J}}\;{\rm{k}}{{\rm{g}}^{ – 1}}\) respectively.

Changes of the Gaseous State into Liquid State: Condensation

When the water vapour or steam is cooled by lowering its temperature, it gets converted into liquid water. This process is called condensation. It may be defined as “the process of changing a gas into a liquid by cooling.”

Let us describe how the process of condensation takes place.

When a gas is sufficiently chilled by lowering its temperature, its particles lose kinetic energy and travel slowly until they attract one another and form a liquid.

Change of Liquid state into Solid state:zing or Solidification

When water is cooled by lowering its temperature, it changes into solid ice. Thus, when waterzes to form ice, there is a change from a liquid state to a solid-state. Thezing point of a liquid is the same as the melting point of its solid form. Thus,zing may be defined as “the process of changing a liquid into a solid by cooling.

Let us describe how the process ofzing takes place.

When a liquid is cooled enough by lowering its temperature, each of its particles loses energy. The particle stops moving and vibrates about a fixed position, and becomes solid.

This figure shows the inter-conversion of three states of matter.

Effect of Change of Pressure: We have learned that the state of matter can be changed into another state by changing temperature. Pressure also determines the state of matter of a substance. The gases are liquefied by increasing pressure and decreasing temperature.

Dry ice (solid \({\rm{C}}{{\rm{O}}_{\rm{2}}}\)) gets directly converted into gaseous \({\rm{C}}{{\rm{O}}_{\rm{2}}}\) on decreasing pressure to one atmosphere. This is the reason why dry ice is stored under high pressure. On increasing pressure, the molecules come close together, the distances between the molecules decrease, and the force of attraction between the molecules increases. Thus, increasing or decreasing the pressure can change the state of matter.

Summary

Changing the pressure and (or) temperature of a substance can change the spaces between the particles, the force of attraction between the particles, and the amount of movement (or kinetic energy) of the particles. 

As a result, the same substance can exist in all three physical states: solid, liquid, and gas, depending on the pressure, temperature, and other factors. Water, for example, exists as a solid in ice at a temperature of \({\rm{0}}\,^\circ {\rm{C}}\) or below under normal pressure. 

At room temperature, it exists as a liquid in the form of water, while at temperatures of \({\rm{100}}\,^\circ {\rm{C}}\) or higher, it exists as a gas in the form of steam. We can conclude from this explanation that there are two elements that determine whether a substance is a solid, liquid, or gaseous state are temperature and pressure.

FAQs

Q.1. What is called interconversion of matter?
Ans: Interconversion of matter is the phenomenon of changing matter from one state to another and back to its original state by changing the temperature and pressure conditions.

Q.2. What is the interconversion of matter explain with example?
Ans: The term interconversion of matter refers to the transformation of one state into another. For instance, consider the transition from a liquid (water) to a solid-state (ice).

Q.3. What do you mean by the interconversion of states?
Ans: The term interconversion refers to the transformation of matter from one state to another. It’s a process in which matter transitions from one state to another and returns to its original condition without changing its chemical composition. Heat can be used to turn solids into liquids. Similarly, liquids can be turned into gases by heating, gases into liquids by cooling, and liquids into solids byzing.

Q.4. Why is a melting point determined in interconversion?
Ans: The energy supplied by the heat is strong enough to overcome the forces of attraction between the particles. The particles leave their fixed position and begin to movely due to a decrease in the force of attraction. As a result, a stage is reached when a solid melt and turns into a liquid.

Q.5. What are the two factors responsible for the interconversion of matter?
Ans: The two factors that cause matter to interconvert are temperature and pressure.

Q.6. State the two uses of interconversion of matter.
Ans: Some uses of interconversion of matter are:
a. Metals are melted by heating, and these molten metals can be converted into alloys, which have many applications.
b. Gases can be condensed to liquids. It is used in the preparation of liquefied petroleum gas, CNG, etc.

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