Gems Chemistry BLog: April 2011

Monday, April 25, 2011

6.2.2-6.2.3

Definition of activation energy
Activation energy is defined as the minimum value of kinetic energy which particles must have before they are able to react.
Three factors that affect the rate of reaction
1 Collision frequency- The higher the frequency the more likely there will be a successive collision therefore the faster the reaction.

2 Energy of collision- For a reaction to take place, the particles must have a certain minimum value for their kinetic energy. This energy is needed to overcome the repulsion between molecules and often to break some bonds in the reactants before they can react (activation energy). Only particles which have a kinetic energy value greater than the Ea will be able to achieve a reaction- have successful collision. KINETIC > Ea

3 Geometry of collision- Since collisions are random, they are likely to occur with the particles in many different orientations. In some reactions, this can be crucial in determining whether or not the collisions will be successful and therefore what proportion of collisions will lead to a reaction.

6.2.1

The kinetic theory describes a gas as a large number of small particles, all of which are in constant, random motion.
The moving particle constantly collide with each other and with the walls of the container.
The picture to the left demonstrate how the atoms move randomly and colliding with each other. This exerts a force, pushing the polystyrene upwards. There is force and area in action so we can draw up that the volume is also the pressure.
In this example, we supply electricity (voltages which is equivalent to temperature) to the mechanic upward and downward motion. When we increase the temperature, the kinetic energy increases represented by the louder the sound and the higher the polystyrene. The kinetic energy is directly proportional to temperature Kelvin as 0 degrees celcius still has kinetic so we need to use the kelvin scale in order to start at 0K or -273 degrees celcius.
Not all particles in a substance at any one time have the same values of kinetic energy, but will have instead a range of values that are reasonably close to each other therefore we have to take the average of these values and this is related directly to its absolute temperature.
Temperature in Kelvin's is proportional to the average kinetic energy of the particles in a substance.