The+role+of+Kinetic+Energy+in+Phase+Changes

​ The Role of Kinetic Energy in Phase Changes = =

__Part one: Basic Knowlege of Kinetic Energy__
====Kinetic energy : *"It is the energy that molecules possess as a result of their motion. " In other words, kinetic energy is the energy which is formed due to the motion of the molecules inside an object. ==== ====There are three kinds of kinetic energy which can exist in a molecule: Rotational energy, Vibrational energy, and Translational energy. ==== ====--- Rotational Energy : The energy which make the molecule to rotate around its axis. ==== ====--- Vibrational Energy : The energy which make the angles between atoms and the bond length change. ==== ====--- Translational Energy : The energy which cause the molecules to travel from place to place in __straight line__. ====

====From the phase of __solid to liquid__, the process is called __melting__, if it is the opposite, the process is called __freezing__. ==== ====<span style="background-color: #ffffff; color: #000000; font-family: 'Comic Sans MS',cursive; font-size: 190%;">From the phase of __liquid to gas__, the process is calle __boiling/evaporating__, if it is the opposite, the process is called __condensing__. ==== ====<span style="background-color: #ffffff; color: #000000; font-family: 'Comic Sans MS',cursive; font-size: 190%;">From the phase of __solid to gas directly__, the process is called __sublimating__, and if it is the opposite, the process is called __depositing__. ====

<span style="background-color: #ffffff; color: #cf00ff; font-family: 'Comic Sans MS',cursive; font-size: 200%;">[[image:phasediagram.gif width="708" height="505"]]
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<span style="font-family: 'Comic Sans MS',cursive; font-size: 180%;">__Special Notes: when we look at the phase changing diagram, all the bond- breaking process happen in the "horrizontal" direction. No bonds are broken except the horrizontal directions!!__ __ Part Three: Practical Applications of Kinetic Energy Changes __ <span style="font-family: 'Comic Sans MS',cursive; font-size: 190%;">Q1：Why Microwave oven can cook food? A1: Because the microwave oven can supply energy through the microwave to the food, which enables the water molecules in the food to absorb energy and to vibrate. Thus, the molecules can bump into each other, and the amount of energy which the food obtains increases, as the result, the food is cooked! Q2: What is IR? A2: IR represents infrared spectoroscopy, and it is light energy with less energy than red light.* *It is used to identify unknown molecules, because the vibrational energy change the frequency of the infrared light slightly, and the energy is absorbed, which enable for us to plot a "spectrum" which is identical for every single molecule, and we can get informations from those "spectrums" __<span style="font-family: 'Comic Sans MS',cursive; font-size: 140%;">References __ =f rom the website www-bioc.rice.ed ==from the website []
 * <span style="font-family: 'Comic Sans MS',cursive; font-size: 180%;">Solid: In the solid phase, when the temperature increases, the internal kinetic energy( vibrational and translational energy) increase, which make the molecules vibrate back and force. Eventually, the translational energy reaches the critical value，which is high enough to help the molecules to break the intermolecular forces which hold the molecules together with their neighbour molecules. As the result, the molecules can pull away from each other instead of stay together with each other. Thus, the molecules break out of the solid phase, and the solids are melt. However, there are still some intermolecular bonds forces exist, but they are much smaller than before, and that's why they form liquid.
 * <span style="font-family: 'Comic Sans MS',cursive; font-size: 180%;">Liquid: When the temperature keep increasing, the liquid possess more energy, and the molecules are able to move faster and faster. Therefore, the translational energy will increase, when it reaches the critical value, the intermolecular bonds between molecules in the liquids will be break. In addition, the temperature will be higher. ( because temperature is the measure of average kinetic energy, which is in three forms of rotational energy, vibrational energy as well as translational energy. To be more easily, average Kinetic energy=temperature=vibrational energy+rotational energy+translational energy)
 * <span style="font-family: 'Comic Sans MS',cursive; font-size: 180%;">Gas: The process of turning liquids into gases is quite similar with the one of turning solid into liquid(melting). However, when the temperature increases, the energy also increases, and when it reaches the critical value, the high vibrational energy enables the atoms to break their bonds, and get rid of the forces of their neighbours, in order to form the less dense gas phase.
 * From the textbook P64
 * From page 63 in textbook