Kinetic theory
Kinetic theory, also known as the Kinetic Theory of Matter or the Kinetic Molecular Theory of Matter, proposes that all matter is made up of small particles, such as atoms or molecules, which are in constant motion. The behavior of these particles varies significantly depending on the phase of matter: solids, liquids, gases, and plasma. In solids, particles are closely packed and vibrate in place with minimal energy, whereas in liquids, they are more spaced out and can flow, adapting to the shape of their container. Gases consist of particles that move rapidly and freely, breaking intermolecular forces entirely, which allows them to occupy the available space in a given environment.
Temperature plays a crucial role in the kinetic theory, as it determines the energy levels of the particles. As temperature rises, particles gain kinetic energy, leading to phase changes, such as the transition from solid to liquid and from liquid to gas. In extreme conditions, such as very high temperatures, gases can become plasma, a state of matter characterized by ionized particles. Kinetic theory is foundational in understanding the physical properties of matter and is supported by scientific observations and experiments that inform our comprehension of molecular behavior.
Subject Terms
Kinetic theory
The Kinetic Theory is also called the Kinetic Theory of Matter or the Kinetic Molecular Theory of Matter. According to the Kinetic Theory, all matter is composed of a large number of small particles, which are atoms or molecules. These particles are constantly in motion and have space between them. The speed at which the particles move depends on the phase of matter—the particles in a gas move much faster than the particles in a solid. The rate at which the particles move also depends on the temperature. The Kinetic Theory attempts to explain how matter behaves in each phase. The theory is based on scientific experiments and observations.
Overview
The Kinetic Theory is used to explain how matter behaves. The theory is based on assumptions regarding the behavior of atoms and molecules. It is impossible to study these particles individually because they are extremely tiny, and matter consists of millions of them. Therefore, scientists apply these assumptions, which are based on observations and experiments, to predict how the particles within matter behave.
Assumptions
All matter is comprised of small particles.
These particles have space between them.
These particles are always in motion. In molecules, this motion is random.
If the particles gain energy, they move faster. This energy is called kinetic energy.
Four Phases of Matter
The four phases of matter are solids, liquids, gases, and plasma. The amount of energy within the particles—the atoms or molecules—determines the phase that matter is in. The particles within a solid have very little energy and are packed closely together. These particles appear to vibrate around a fixed point and are not free to spread out. Intermolecular forces of attraction keep the particles packed tightly. This is why a solid stays in a specific shape. For example, if you put a brick in a box, the brick will not take the shape of the box. It will still be in the shape of a brick.
The particles in a liquid have more energy than those in a solid. These particles are also farther apart and have more freedom to move and spread out. As in a solid, particles in a liquid are pulled toward each other by intermolecular forces, but these forces are not as strong. This is why a liquid can change shape. For example, milk in a carton will take on the shape of the carton. If you pour the milk into a glass, it will take on the shape of the glass.
The molecules within a gas have a great deal of energy. They can move quickly and spread out. They move with enough force to break all intermolecular forces. They can move independently of each other and put as much distance between themselves as possible. For example, if you boil water, the steam (which is water vapor) will spread out into the air.
Plasma is abundant throughout the universe. Most stars, including the sun, have plasma in them. The wind in our solar system is also made of plasma. Plasma is an ionized gas—it is comprised of free-floating ions and free electrons. While naturally occurring plasma is not common on Earth, manmade plasma is. Neon signs and fluorescent light bulbs are examples of plasma. Both have tubes filled with gas. When the light is turned on, electricity flows through the tube, which charges the gas. This creates plasma inside the tube.
Phase Changes
The Kinetic Theory can be used to explain the effect of temperature on matter. Suppose you put a block of ice into a pot and then put the pot on a stove. The ice is a solid, so the particles within it are moving very slowly and are close together. As you heat the pot, however, the ice melts—the matter changes from a solid to a liquid. The water—the liquid—will take on the shape of the pot. When the liquid boils, it begins to change into water vapor. In time, the liquid becomes a gas.
According to the Kinetic Theory, these phase changes occur because temperature causes the particles within matter to gain kinetic energy. The particles in a solid move very slowly and vibrate around a fixed point. However, as the temperature increases, they vibrate faster. The particles gain more freedom and the solid undergoes a phase change. The same is true of a liquid. As the temperature of the liquid increases, the particles within the liquid gain energy. They collide with greater force and are able to break the intermolecular forces.
If a gas is heated to an extremely high temperature—thousands of degrees—the particles gain so much kinetic energy that they nearly explode. They collide so strongly that the electrons break out of the atoms. This creates plasma.
Bibliography
Friedle Sarah. "The Kinetic Theory of Matter: Definition & the Four States of Matter." Education-portal.com. Education Portal. Web. 15 Dec. 2014. http://education-portal.com/academy/lesson/the-kinetic-theory-of-matter-definition-the-four-states-of-matter.html
"Kinetic Theory & Change." Hometrainingtools.com. Home Training Tools, LLC. Web. 15 Dec. 2014. http://www.hometrainingtools.com/a/kinetic-theory-phase-change-teaching-tip
"Kinetic Theory of Gases." NASA: Glenn Research Center. National Aeronautics & Space Administration. 12 June. 2014. Web. 15 Dec. 2014. http://www.grc.nasa.gov/WWW/k-12/airplane/kinth.html
"The Kinetic Theory of Gases & the Ideal Gas Law." Sparknotes.com. Spark Notes, LLC. Web. 15 Dec. 2014.
"The Kinetic Theory & Phase Change." Chemistry Class. The Internet Science Room. Web. 15 Dec. 2014. http://crescentok.com/staff/jaskew/isr/chemistry/class16.htm
Kurtus, Ron. "Kinetic Theory of Matter." School-for-champions.com. School for Champions. 26 Nov. 2011. Web. 15 Dec. 2014. http://www.school-for-champions.com/science/matter‗kinetic‗theory.htm#.VI74qSvF‗rA
"States of Matter." Chem4Kids.com. Rader's Chem4Kids.Com. Web. 15 Dec. 2014. http://www.chem4kids.com/files/matter‗states.html
"What is the Kinetic Molecular Theory?" Tellmewhyfacts.com. Tell Me Why Facts. Web. 15 Dec. 2014. http://tellmewhyfacts.com/2007/10/what-is-kinetic-molecular-theory-of.html