Collision theory

In chemistry, collision theory is states that in order for a chemical reaction to occur atoms, molecules or chemical species, have to collide. Collision theory used to predict the rates of chemical reactions, particularly for gases. This theory was proposed in 1916 by German chemist Max Trautz and British scientist William Lewis.
This theory is based on the assumption that for a chemical reaction to occur it is necessary for the reacting species. for Example  atoms or molecules, to come together or collide with one another. Only a certain percentage of the collisions cause any noticeable or significant chemical change these successful changes are called  successful and good collisions.
The successful collisions have enough energy. This  also known as activation energy. According to collision theory, in order for a chemical reaction to occur, the chemical entities have to collide. Not all collisions, however, bring about chemical change. The greater the temperature, the higher the probability that molecules will be moving with the necessary activation energy for a reaction to occur upon collision.

Activation energy
Dutch physical chemist Jacobus van’t Hoff, Swedish physical chemist Svante Arrhenius introduced term  activation energy.
Activation energy is the minimum amount of energy that is required to activate atoms or molecules to a condition in which they can undergo chemical transformation or physical transport. The activation energy” is the difference between the maximum energy and the energy of the reactants.
Activation energy also known as energy barrier This is the minimum impact energy required for a chemical reaction to take place. In a reaction, the reactant molecules come together and chemical bonds are stretched, broken and formed in producing the products. During this process the energy of the system increases to a maximum, then decreases to the energy of the products.
 The greater the temperature, the higher the probability that molecules will be moving with the necessary activation energy for a reaction to occur upon collision.

Temperature and
Collision theory
Temperature is also a factor in collision theory. Essentially, an increase in temperature increases the average speed of the reactant molecules, the number or frequency of collisions   and fraction of molecules having kinetic energy higher than the activation energy.

Internal energy
The expression for internal energy was defined in 1850 by German physicist Rudolf Clausius.  Internal energy is the sum of potential energy of the system and the system’s kinetic energy. The change in internal energy of a reaction is equal to the heat gained or lost (enthalpy change) in a reaction when the reaction is run at constant pressure. The internal energy of systems that are more complex than an ideal gas can’t be measured directly. But the internal energy of the system is still proportional to its temperature.

Thermodynamics
Thermodynamics is defined as the branch of science that deals with the relationship between heat and other forms of energy, such as work. It is frequently summarized as three laws that describe restrictions on how different forms of energy can be inter converted.
The Laws of Thermodynamics
First law: Energy is conserved; it can be neither created nor destroyed.
Second law: In an isolated system, natural processes are spontaneous when they lead to an increase in disorder, or entropy.
Third law: The entropy of a perfect crystal is zero when the temperature of the crystal is equal to absolute zero (0 K).

Kinetic energy
Atoms and their components are in motion, so all matter possesses kinetic energy. On a larger scale, any object in motion has kinetic energy.
Kinetic energy is the energy an object possesses due to its motion. An object of mass m moving at velocity v has a kinetic energy equal to ½mv2. An example of kinetic energy is a swinging pendulum. There are many forms of kinetic energy vibrational, rotational and translational.
 Kinetic energy can also be transferred from one body to another in a collision, which can be elastic or inelastic. One example of an elastic collision would be one billiard ball striking another.
 Kinetic energy can be converted into other forms of energy and vice versa. For example, kinetic energy can be converted into electrical energy by a generator or into thermal energy by the brakes on a car.
 Thermal energy can be converted to kinetic energy by a steam turbine, and chemical energy can be converted to kinetic energy by an internal combustion engine.
Kinetic energy of a gas is directly proportional to temperature. As temperature increases, molecules gain energy and move faster .

Calculate the Kinetic Energy
Kinetic energy can be due to vibration, rotation, or translation. The kinetic energy of any object can easily be determined with an equation using the mass and velocity of that object. The formula for calculating kinetic energy (KE) is KE = 0.5 x mv2     or  KE = 1/2 x mv2   . For Example   
a police officer fired 10  gram bullet  with a velocity of 600 meters/second at a target. What’s the bullet’s kinetic energy? Using the equation to find kinetic energy,  remembering to convert from grams to kilograms first to keep the system of units consistent throughout the equation
KE = 1/2 x mv2     
= ½(0.010 kg) x (600 m/s)2 =1,800 J

Max Trautz  
Max Trautz  was a German chemist. He is also known as the founder of collision theory together with the British scientist William Lewis. But he was the first to Publish  the collision theory work. Trautz published his work in 1916, Lewis published it in 1918. Max Trautz was very productive with over 190 scientific publications especially in the field of chemical kinetics. But due to World War at that time they stay unaware of each other’s work. Max Trautz  was the first to investigate the activation energy of molecules by connecting Max Planck’s new results concerning light with observations in chemistry.

William Lewis
  William Lewis was British Brunner Professor of Physical Chemistry at the University of Liverpool.  He was the author of “A System of Physical Chemistry”.  In 1918 he propounded his theory of chemical reaction which came to be called the “Collision Theory”. A similar theory was also propounded by Max Trautz in Germany in 1916.