Collision Theory related to Science under Physics

Editor's Notes

• #19: The collision theory states that reacting substances must come into contact (collide) with enough activation energy, and in the correct orientation (facing the correct way), so that their electron shells can rearrange to form the products of the reaction. Therefore, any factor which changes the frequency or energy of the collisions will change the rate of the reaction.
• #23: All substances are comprised of millions of tiny particles in constant motion. These particles are colliding with each other constantly in any substance however all collisions between particles do not result in a reaction.
• #24: All substances are comprised of millions of tiny particles in constant motion. These particles are colliding with each other constantly in any substance however all collisions between particles do not result in a reaction.
• #25: Collision theory explains why different reactions occur at different rates, and suggests ways to change the rate of a reaction. Collision theory states that for a chemical reaction to occur, the reacting particles must collide with one another. The rate of the reaction depends on the frequency of collisions. The theory also tells us that reacting particles often collide without reacting. For collisions to be successful, reacting particles must (1) collide with (2) sufficient energy, and (3) with the proper orientation.
• #26: If the two molecules A and B are to react, they must approach closely enough to disrupt some of their existing bonds and to permit the creation of any new ones that are needed in the products. Such an encounter is called a collision.
• #27: The more frequently they collide, the faster the rate of reaction.
• #28: Particles that lack the necessary kinetic energy may collide, but the particles will simply bounce off one another unchanged. An ineffective collision (A) is one that does not result in product formation. An effective collision (B) is one in which chemical bonds are broken and a product is formed. In the first collision, the particles bounce off one another and no rearrangement of atoms has occurred. The second collision occurs with greater kinetic energy, and so the bond between the two red atoms breaks. One red atom bonds with the other molecule as one product, while the single red atom is the other product. The first collision is called an ineffective collision, while the second collision is called an effective collision.
• #29: Even if two molecules collide with sufficient activation energy, there is no guarantee that the collision will be successful. In fact, the collision theory says that not every collision is successful, even if molecules are moving with enough energy. The reason for this is because molecules also need to collide with the right orientation, so that the proper atoms line up with one another, and bonds can break and re-form in the necessary fashion. However, because molecules in the liquid and gas phase are in constant, random motion, there is always the probability that two molecules will collide in just the right way for them to react.
• #31: As shown in figure 1, two atoms of Nitrogen react with two atoms of Oxygen to yield two molecules of Nitrogen Oxide. The shared atoms form a bond by completing the valence shells of both atoms.
• #32: As shown in figure 2, a chemical reaction does not take place if the collision between molecules does not have sufficient energy to break the bonds in the reactants and if the molecules are not properly aligned.
• #33: As shown in figures 3 and 4, no reaction can take place between two particles if they are far apart. To form new bonds, atoms must come in contact with each other and have correct relative orientations so that the correct bonds are broken, atoms transfer to the correct positions.
• #35: The substances or particles that enter and is changed in the chemical reaction are called reactants and the substances that are formed are called products.
• #36: The reactants (left part of the equation) are carbon dioxide, water, and light while the products (right side of the equation) are sugar and oxygen. But for a chemical reaction to occur, several things must happen:
• #37: The particles must come into contact with one another or collide. When the particles collide, the particles must be aligned correctly so that the right parts of the atoms or molecules are exposed. If they are not oriented correctly, no chemical reaction will take place 3. The particles must collide with enough energy to break their chemical bonds. The amount of energy that must be available for a reaction to occur is often referred to as the activation energy. It is the measure of the change in the concentration of the reactants or products.
• #39: The particles must come into contact with one another or collide. When the particles collide, the particles must be aligned correctly so that the right parts of the atoms or molecules are exposed. If they are not oriented correctly, no chemical reaction will take place 3. The particles must collide with enough energy to break their chemical bonds. The amount of energy that must be available for a reaction to occur is often referred to as the activation energy. It is the measure of the change in the concentration of the reactants or products.
• #40: On the other hand, if the particles have energy that is less than the activation energy, the collision is not effective, and they just bounce off each other unchanged.
• #41: The figure above shows a man trying to push a rock over the cliff. For the man to push the rock, he needs to have enough energy. If the man does not have enough energy, the rock will not move down the cliff. This energy needed for the man to push the rock over the cliff represents the activation energy.
• #43: Increasing the temperature also increases the reaction rate. Remember, temperature measures a system's average kinetic energy. So, raising the temperature increases the kinetic energy of the molecules. The molecules move faster inside their container. What's the result? More collisions! And more collisions create a faster reaction! But, there's more. For a reaction to occur, the collision needs to overcome the activation energy. With more kinetic energy, they are more likely to overcome the barrier. So, the reaction rate increases.
• #44: Hot water Tap water Cold Water Since temperature is the highest in hot water it is expected that sugar will be easier to dissolve in it, tap water comes next and cold water has the slowest solubility du to its low temperature.
• #45: The rate of a chemical reaction is affected by the concentration of reacting substances. The term concentration refers to the number of particles present in a given volume of solution. Concentration may also mean a measure of how much of of the solute (something to be dissolved) is dissolved in a solvent (dissolving medium) to form a homogeneous mixture. So, a higher concentration means there is more of the solute in the solution.
• #46: Increasing the concentration of the reactants speeds up the reaction rate. Imagine a synthesis reaction between two molecules. The generic balanced chemical equation would be A+B→AB. Let’s say we increased the concentration of reactant A. That means there are more molecules of reactant A per volume. So, reactant B is more likely to collide with reactant A and produce a reaction. More collisions equal faster reactions. 
• #47: In a reaction between a solid and a liquid, the more finely divided a solid is, the faster is the rate of reaction. Likewise, as you powdered a solid, its surface area becomes greater, thus the particles have higher chance of colliding and faster reaction happens.
• #48: Let's imagine an ionic compound. We know they form a crystal lattice. So, you have repeating unit cells of ions, that build the overall structure. But, that means some of the ions are buried inside the crystal. Only the ions on the surface can react. Let's imagine we took an ionic crystal and smashed it with a hammer. That would be a lot of fun! But, we would expose some of the ions in the center of the crystal. Now they can react.