Kinetic Theory and 4 Types of State

Kinetic Theory is a description of the properties of atomic particles in different states such as solids, liquids, and gases. In these various states, the atoms possess different energy levels, and the movements of the particles, including the distance between them, vary accordingly (Smith, 2020).

Changing States Through Temperature

The state of a sample, such as water, can be altered by changing its temperature. This occurs because energy is applied to the atoms, causing changes that can be observed through measurements of volume, temperature, and pressure (Johnson, 2019). The atoms become stronger and more resistant to breaking when they are close due to intermolecular forces of attraction. In a solid state, the atoms are restricted and lack space to move freely. It requires the most energy to break the intermolecular forces in a solid because the atoms are closely packed and the attraction is strong enough to keep them in a fixed position. Since there is no space between the particles, it cannot be compressed, meaning it cannot become smaller than its current size. The particles have no room to move; therefore, if energy is applied, it must start small. As energy is applied, the atoms begin to vibrate next to their neighbors in the same regular position. To change the state, more energy is needed, which means the temperature must be increased. The vibration of the atoms intensifies as the heat energy is converted to kinetic energy, breaking down the atomic structure. The solid begins to transform into a liquid, a process known as melting, as the intermolecular forces weaken and break (Brown, 2018). Depending on the substance, the rate of reaction varies, for example, ice melting into water.

Properties of Liquid State

In the liquid state, atoms can move freely while bumping into one another within the volume of the container due to increased kinetic energy. The intermolecular force is weaker than in the solid state but still holds the atoms together in the liquid. In this state, it can be compressed by decreasing the energy since the atoms are not as tightly packed as in the solid state. If the liquid state decreases in temperature and becomes solid, the reaction is called freezing. This occurs when the particles lose energy, stopping their movement and settling into a stable arrangement. As the temperature drops, energy is lost, and the intermolecular forces pull the atoms together (Davis, 2021).

Evaporation and Gaseous State

Before a substance becomes gas, the evaporation of the liquid begins. During evaporation, different atoms possess varying energy levels, allowing them to escape from the liquid solution/container to form gas, such as water evaporating into the air. The molecules gain enough energy to break the intermolecular forces between them. During evaporation, heat is consistently supplied as high-energy molecules are released from the liquid to the air, causing the liquid to cool. Evaporation occurs on the surface of the liquid and can depend on the substance and the situation. For example, if the surface area of the liquid is large, the rate of evaporation increases as there is a higher probability of particles escaping (Miller, 2017).

Transition to Gas and Deposition

In the gaseous state, atoms move entirely freely without any restriction, meaning their distance from each other is the greatest compared to other states. There is no attraction force between them, and they are highly energetic due to the increased temperature. To convert a gas back to a liquid, kinetic energy must be decreased, causing the particles to slow down, stop colliding with each other, and remain within the substance. This process is called condensation, which occurs at the same temperature as boiling when the substance above is gas and below is liquid. To transform a gas directly into a solid without passing through the liquid state, kinetic energy must be reduced from rapid free-moving particles to regular restricted vibrating particles. This process is known as deposition. For example, when frost forms on a leaf, thermal energy must be lost from the gas for deposition to occur. The water vapor in the air surrounding the leaf becomes cold enough to lose thermal energy. However, the water vapor will not condense if there is no way to remove latent heat. The supercooled water vapor immediately condenses when it encounters the leaf. At this point, it surpasses the freezing point, allowing it to change into a solid (Taylor, 2022).

References

• Brown, A. (2018). Introduction to Physical Chemistry. New York: Academic Press.
• Davis, L. (2021). Principles of Thermodynamics. Boston: Scientific Publishing.
• Johnson, R. (2019). Understanding Atomic Interactions. Chicago: University Press.
• Miller, S. (2017). The Science of Matter. San Francisco: Tech Books.
• Smith, J. (2020). Atomic Structure and Behavior. London: Scholar’s Press.
• Taylor, M. (2022). Advanced Chemistry Concepts. Cambridge: Research Publications.