Understanding Collision Theory in Chemical Reactions

Understanding Collision Theory in Chemical Reactions – Chemical reactions can occur anywhere, even around us, anywhere and anytime. Not only in the laboratory, materials that interact to form new products are called chemical reactions. For example, cooking or cleaning the house also involve activities that can cause chemical reactions.

Chemical changes also occur in the human body, for example during exercise or even breathing. Chemical reactions are an integral part of technology, culture and human life. Iron smelting, glass making, tea and cheese making are examples of activities involving chemical reactions that have been used for thousands of years. Many chemical reactions occur on Earth, in the atmosphere, and in the oceans.

Chemical reactions or chemical changes occur everywhere, from the body’s metabolism of food to the absorption of sunlight into the human body. There are two kinds of changes, namely chemical changes and physical changes. A chemical reaction is a series of processes in which one or more substances change into one or more substances and produce new products. Substance is a chemical element or compound. Chemical reactions rearrange the atoms of the reactants into different substances. Chemical reactions usually occur in connection with physical changes, heat production, color changes, etc. The rate at which a reaction changes depends on and is affected by factors such as pressure and temperature.

However, do you know that one of the theories that discusses the series of chemical reaction processes is the collision theory? If you don’t know and want to find out more, in this discussion we will try to discuss the collision theory in full.

Furthermore, we will review the discussion of the collision theory in this chemical reaction below!

Definition of Collision Theory

Collision theory is a theory proposed independently by Max Trautz in 1916 and William Lewis in 1918 that qualitatively explains how chemical reactions occur and how reaction rates change in various reactions. Collision theory states that when closely matched reactant particles collide, only a certain percentage of collisions result in a real or significant chemical change; This successful change is called a successful collision. In a successful collision, there is enough energy at the time of impact, also known as activation energy, to break the existing bonds and form all the new bonds. This produces reaction products. Increasing the concentration of reactant particles or increasing the temperature,

When a catalyst is involved in collisions between reacting molecules, less energy is required for the chemical change to occur, and therefore more collisions have sufficient energy for the reaction to occur. Hence the rate of reaction increases.

Collision theory is closely related to chemical kinetics, collision theory qualitatively explains how chemical reactions occur and how reaction rates change in various reactions. Max Trautz and William Lewis found that when suitably reacting particles collided, only a certain percentage of the collisions caused a real or significant chemical change; This successful change is called a successful collision. This is the basic idea behind the collision theory formation process.

Very successful collisions have sufficient energy, also called activation energy. On collision, it breaks the existing bonds and forms all new bonds. This produces reaction products. Increasing the concentration of reactant particles or increasing the temperature, which results in more and therefore more successful collisions, increases the rate of reaction.

When a catalyst is involved in collisions between reacting molecules, less energy is required for the chemical change to occur, and therefore more collisions have sufficient energy for the reaction to occur. Thus, the rate of reaction increases by

Originator of the Collision Theory

  • Max Trautz (19 March 1880 – 19 August 1960) was a German pharmacist.

He was very prolific and published more than 190 scientific publications mostly in the field of chemical kinetics. He was the first to study the activation energy of molecules, combining Max Planck’s new findings about light with observations in chemistry.

Max Trautz Born March 19, 1880 Karlsruhe, Baden Died August 19, 1960 (aged 80) Karlsruhe, West Germany German Nationality German Alma mater Karlsruhe University Known as Theory of Collision Career Karlsruhe Institute of Chemistry University of Heidelberg Heidelberg also known as British PhD. collision theory with Lewis. While Trautz published his work in 1916, Lewis published it in 1918. Due to World War II, however, they were not aware of each other’s activities.

  • William Cudmore McCullagh Lewis, FRS (29 June 1885 – 11 February 1956)

William Lewis was an English pharmacist and academic. He is the Brunner Professor of Physical Chemistry at the University of Liverpool.

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He was born in Belfast to Edward Lewis, a linen merchant, and his wife Francis Welsh McCullagh. He studied at Bangor Grammar school. Together. Down and the Royal University of Ireland, Belfast, where he studied physics and chemistry. After receiving his master’s degree in 1906, he became a demonstrator for one year and then moved to England to study physical chemistry at the University of Liverpool. There he received a scholarship to work for one year at the University of Heidelberg.

He was appointed the Brunner Professor of Physical Chemistry in 1913 (until 1937, when he entered the Chair of the Association of Inorganic Chemistry). In 1918, he presented his theory of chemical reactions, which was later called the “collision theory”. Max Trautz proposed a similar theory in Germany in 1916, which Lewis was not aware of because of the First World War.

In 1926 he was elected a Fellow of the Royal Society. The candidate quote describes him as follows: Respect his research in physical chemistry. He made the most valuable and important studies of the energy relations of chemical change, and was among the first to apply the quantum theory of energy to chemical reactions. His pioneering work in this area proved invaluable and opened up a very promising field of research. Author: “Physical Chemical Systems.” Published a number of original publications on many issues in physical chemistry, as well as a long series of publications on the theory of radiation reactions.

He was appointed the first Grant-Brunner Professor of Physical and Inorganic Chemistry in 1937, a position he held until 1948.

He died at Malvern in 1956. He married Jeannie Waterson Darrock, with whom he had a son, Ian, who became a physicist at the Harwell Atomic Energy Research Institute.

Theory of Collisions and Chemical Reactions

According to the collision theory, chemical reactions occur when molecules collide. But according to this theory, not all collisions cause chemical reactions. This is because every moving molecule has kinetic energy, the faster the molecule moves, the greater the kinetic energy. If a molecule has high kinetic energy to begin with, the molecules collide harder, so the chemical bonds break. The breaking of these chemical bonds is the first step in forming a product. If the molecule has a low kinetic energy, the movement of the molecule is slower, the bonds are difficult to break to form products.

For a reaction to occur, the total kinetic energy of the molecules must be equal to or greater than the activation energy. Activation energy is the smallest amount of energy required to start a chemical reaction. If the energy is low, the molecule stays intact and no changes occur as a result of the collision.

From the explanation above, it can be concluded that there are two conditions for the collision to produce a reaction. First, the collision has the correct orientation and has a kinetic energy equal to or greater than the activation energy.

In case of a successful collision, there is enough energy, e.g. activation energy, when bonds are broken and new bonds are formed. During the process, reaction products are formed. An increase in the concentration of reactants or an increase in temperature causes an increase in collisions, which increases the number of successful collisions and thereby increases the reaction rate.

If the catalyst is involved in the collision process of the reacting molecules, the energy required to continue the chemical reaction is lower. Therefore, the number of collisions that have enough energy to complete the reaction, so the rate of reaction increases.

Collision Theory and Reaction Rates

Do you know? It turns out that we often apply the principle of reaction speed in our daily life. For example, when our mothers fry meat. Be sure to cut the meat into small pieces, the goal is to increase the contact surface. So that the reaction of raw meat becomes tender faster.

Sometimes mom adds unripe papaya to the meat stew to cook the meat faster. Because papaya contains the enzyme papain which acts as a catalyst and speeds up the decomposition of meat.

In addition, the principle of the reaction is also used in industry. For example, in the production of sulfuric acid using a vanadium pentaoxide catalyst, in the production process of ammonium fertilizers with an (Fe) catalyst, in the process of forming natural gas into various alcohol products using an active zeolite catalyst, etc. .

Reaction rates are also used in the automotive industry. The principle of operation of motorized vehicles, gasoline from the tank flows through the carburetor to the combustion chamber. The gasoline that enters the combustion chamber is already in the form of a gas with a smaller particle size than in liquid form. So it’s easier to burn. The reaction rate in collision theory has a meaning as a theory which states that reacting particles or reactants must collide for a reaction to occur. The reaction rate is the change in the concentration of a reactant or product per unit time. The measurement of the speed quantity can be seen as a fast or slow quantity based on a chemical reaction. The reaction rate has units.

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The reaction rate indicates the rate of decrease in the number of reactants or the rate of increase in the number of products per unit time. Units for the amount of a substance are different, such as grams, moles, or concentration. The units of time are seconds, minutes, hours, days or years. In chemical reactions, many chemical substances are used as solutions or gases in a confined space, in this case the rate of reaction is used as a unit of concentration (molarity).

At the beginning of the reaction, the reactants are at their maximum, while the products are at their minimum. After the reaction occurs, more products are formed because the reactants decrease with time, especially M/s (molars per second).

Factors Affecting Reaction Rate

Several factors affect the speed of the reaction. Here we explain some of these factors.

– Temperature

Kinetic energy increases with increasing temperature. Therefore, the number of molecules whose energy is higher than the threshold energy also increases. Consequently, the number of effective collisions between reacting molecules also increases. However, the rate of reaction is not always equal to the increase in temperature. Certain reactions, such as biological reactions catalyzed by enzymes, can be slowed down by increasing the temperature because the enzymes can lose their activity.

– The concentration of the reactants

The speed of the reaction is directly proportional to the concentration of the reactants. theoretically, the reaction rate should increase with increasing concentration, since the rate is directly proportional to the frequency of collisions. The rate of reaction decreases with time as the concentration of the reactants decreases.

– Surface area

The rate of reaction increases as the surface area of ​​the solid reactants increases. Solid surface can be improved by turning it into a fine powder. For example, the reaction between zinc and hydrochloric acid occurs in seconds when zinc metal is reduced to a fine powder.

But the reaction is slower if it is in the form of zinc wire. This also applies to solid catalysts, which are usually used in chemical reactions as fine powders. For example, finely ground nickel is used in the hydrogenation of crude oil.

  • Catalyst

A catalyst is a substance that changes the rate of a reaction without consuming it or causing a chemical change to occur during the reaction. Catalysts increase reaction rates by providing new pathways with lower activation energies for reactions.

In a reversible reaction, the catalyst lowers the activation energy of the forward and reverse reactions at the same rate and helps to achieve a correct balance. Certain substances can slow down the reaction rate.

These are usually called negative catalysts or inhibitors. They prevent reactions, form relatively stable complexes and require more energy. Thus, the reaction rate decreases.

Chemical reactions occur when there are collisions between particles with sufficient energy, this energy is called activation energy. Not all elements of chemical compounds can react with each other, only elements with sufficient activation energy can carry out reactions, most of these elements do not have sufficient activation energy. Well, for such conditions, we need a substance that allows all the particles to reach the activation energy to react with each other, increasing the reaction rate. In these conditions, the addition of a catalyst is required, the addition of a catalyst provides a significant change in activation energy. Catalysts provide a special pathway for a reaction to take place, these special pathways have a low activation energy so that they can increase collisions between particles. As a result, the reaction rate increases.


This is a brief discussion of the definition of collision theory. The discussion this time does not only discuss the definition of collision theory but also discusses the biography of the originator of collision theory, the relationship between collision theory and chemical reactions and the rate of reactions that are interrelated. Understanding the meaning of collision theory makes us understand more about what a chemical reaction is and its effects through several examples of chemical reactions that without us realizing it, we also always do it in our daily activities.

This is a review of the meaning of collision theory. For Sinaumed’s who want to learn everything about the meaning of collision theory and other knowledge related to chemistry, you can visit sinaumedia.com to get related books.

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Author: Pandu Akram