Question

According to the collision model of chemical reactions, how is it possible that two molecules can collide but not react? (Chapter 16)

Short answer

According to the collision model of chemical reactions, two molecules can collide but not react if they do not have the correct orientation during the collision or if the energy of the collision does not meet the activation energy required for the reaction to happen. These two factors, orientation and energy threshold, are crucial in determining whether the colliding molecules will undergo a chemical reaction or simply bounce off each other without any chemical change.

Step-by-step solution

Understand the Collision Model of Chemical Reactions

The collision model states that for a chemical reaction to take place, the reacting molecules must collide with each other. This model involves looking at the rate at which reactions occur, which depends on the number and energy of these collisions. However, not every collision between molecules will result in a reaction. Reactions only occur if certain conditions are met during the collision.

Consider the Effect of Orientation during Collisions

The orientation of the colliding molecules is a crucial factor in determining whether the molecules will react or not. For a reaction to occur, the molecules must collide in a specific orientation that allows the breaking and formation of chemical bonds between them. If the orientation is not correct, the reaction will not occur, and the molecules will merely bounce off each other without undergoing any chemical change. This is one reason why two molecules might collide but not react.

Examine the Energy Threshold for Reactions

The second factor necessary for a reaction to occur is the energy of the collision, which must reach or exceed a specific threshold known as the activation energy. The activation energy is the minimum energy required for the reactants to form the products. If the collision does not meet this energy threshold, the molecules will not have enough energy to overcome the barrier and undergo the reaction. In essence, the molecules will not have the necessary energy to break existing bonds and form new ones. In conclusion, two molecules might collide but not react if they do not have the correct orientation or if the energy of the collision does not meet the activation energy required for the reaction to happen.

Key concepts

Activation Energy

Activation energy plays an essential role in determining whether or not a chemical reaction will occur when two molecules collide. Imagine a mountain that molecules must ascend to react; activation energy is akin to the height they need to climb over. If the molecules don’t have enough energy, they cannot cross this mountain.

In chemical reactions, activation energy is the minimum energy threshold that reactants must possess to convert into products. Without sufficient energy, the molecules will simply bounce off each other rather than initiating a chemical reaction.

• Higher activation energy means fewer collisions result in reactions, as fewer molecules have this required energy.
• Reactions can be sped up by increasing the temperature, providing more energy to the molecules to meet this threshold.

Understanding activation energy helps chemists control and modify conditions to make reactions more efficient, crucial in industrial chemical processes.

Molecular Orientation

The orientation of molecules during a collision is another fundamental aspect of whether or not a chemical reaction will occur. Think of molecular collisions as a dance; if the partners are not aligned correctly, they can't move together harmoniously to create something new.

Not every collision leads to a reaction because molecules need to align in a specific orientation for successful interaction. Essential bonds must break, and new ones must form in specific ways, requiring precise alignment.

• Only the right orientation allows for the necessary contact between the right parts of the molecules.
• Even with the right energy, wrong orientation will hinder reactions from happening.

By understanding molecular orientation, scientists can better predict and influence the outcomes of potential reactions in the lab or in nature.

Chemical Reactions

Chemical reactions involve transformations at the molecular level and require specific conditions to proceed. They occur when molecules, the smallest units of compounds, interact in ways that lead to a change in their structure, resulting in new substances.

For a chemical reaction to occur under the collision model, certain criteria are necessary: the correct activation energy and the proper orientation of the molecules. These factors ensure that when molecules collide, bonds are effectively broken and formed, allowing the reaction to proceed.

• Successful reactions lead to products that are different from the initial reactants.
• The reaction process transforms the energy, structure, and characteristics of the substances involved.

Through understanding chemical reactions, scientists can create everything from pharmaceuticals to materials that improve our everyday lives. Recognizing the role of energy and molecular orientation is key to mastering this transformative science.