Analysing Changes Between Liquids and Solids

States of Matter

Solids, liquids, and gases are the three types of matter we encounter in everyday life. Let’s take a look at the transition from solids to liquids and the melting point of solids. The liquid phase is distinguished by large-scale relative particle movement, which results in liquids displaying elastic and viscous behaviour. Solids are rigid with immovable particles.

The standard microscopes display well-defined particles that are the same in both phases and a single type of forces/bonds that are the same in both phases. When a solid is heated, the bonds between the particles weaken, allowing the particles to slide and ultimately flow, resulting in the conversion of a solid into a liquid. However, because materials from different material classes have varying melting enthalpies and melting temperatures, these discrepancies must be due to microscopic processes.

Solid state

The state of matter that has the highest intermolecular forces, lowest compressibility, highest density and fixed volume and shape is called the solid state—for example, rock and wood.

Liquid state

The state of matter with intermediate intermolecular forces, intermediate compressibility, intermediate density, and fixed volume but no fixed shape is called a liquid state—for example, milk and water.

Interconversion of states of matter

Conversion of solid to liquid is called fusion, and conversion of liquid to solid is called solidification.

Changing states of matter

Any state of matter changes when there is a change in the energy of the substance, generally the thermal energy. When the molecules get energy in the form of heat, they start vibrating rapidly. When the amount of energy provided is increased, the molecules will split from the material due to increased vibration. Hence, one state of matter changes into another.

Conversion of a solid into a liquid

For the conversion of matter from its solid into its liquid state, consider the example of ice cubes. The ice cubes are kept in a beaker, which is kept on a bunsen burner. When the heat reaches the solid ice cubes present in the beaker, they start melting into the liquid form. The molecules of the ice cubes gain sufficient energy from the heat and start vibrating within the lattice. As the temperature of the beaker increases, the vibration in the molecules also increases. As a result, the molecules split into different parts, and the liquid state of water is reached.

In the event of a change of state, one thing to keep in mind is that, although heat is being delivered, there will be no increase in temperature. The ice absorbs the heat energy and converts it into water. There is no difference in temperature until all the ice has melted. During a transition of state, a substance’s solid and liquid forms coexist in equilibrium. The process of obtaining a solid from a liquid is called fusion or freezing, and it involves removing heat from the sample. Now that we’ve learned about shifting states of matter and liquid-solid conversion, let us understand the melting point.

Terms related to changing states between liquid and solid

Melting point

Melting point refers to the temperature at which solid and liquid phases coexist. It is specific to the material and is influenced by the amount of pressure exerted on the body. The melting point decreases as pressure rises. By altering the equilibrium of the solid and liquid states, pressure influences the melting rate.

Vapour pressure

The pressure at which a gas coexists with its solid or liquid phase is known as vapour pressure. Faster molecules that break away from a liquid or solid and enter the gas phase cause vapour pressure. The vapour pressure of a material is determined by both the substance and the temperature of the substance; when the temperature rises, the vapour pressure increases as well.

Partial pressure

The partial pressure of a gas is the amount of pressure that a gas will generate if it occupies the total available volume.

Dalton’s Law of Partial Pressure

Dalton’s Law of Partial Pressure was given by John Dalton (1766–1844). It states that when perfect gas behaviour occurs, such that no type of reaction takes place between them, then the total pressure of a mixture of gases is equal to the sum of the partial pressures of the constituent gases. Dalton’s law is based on kinetic theory, which states that each gas generates its own pressure through molecular collisions, regardless of the presence of the other gases. It is congruent with Pascal’s Principle, which states that in a closed container, a pressure change in one part of a fluid at rest is transmitted without loss to every portion of the liquid and the walls of the container.

Conclusion

Solids, liquids, and gases are the three types of matter we encounter in everyday life. The state of matter with the highest intermolecular forces, lowest compressibility, highest density, and fixed volume and shape is called a solid state. The state of matter with intermediate intermolecular forces, intermediate compressibility, intermediate density, and fixed volume but no fixed shape is called a liquid state. 

Any state of matter changes when there is a change in the energy of the substance, generally the thermal energy. When the molecules get energy in the form of heat, they start vibrating rapidly. When the amount of energy provided is increased, the molecules will split from the material due to increased vibration. Hence, one state of matter changes into another.