1. Lowering Temperature:
* kinetisk energi: Reactions occur when molecules collide with enough energy to break bonds and form new ones. Lowering temperature reduces the average kinetic energy of molecules, leading to fewer successful collisions.
* Aktiveringsenergi: Every reaction has an activation energy barrier that molecules must overcome to react. Lower temperatures make it harder for molecules to reach this energy level.
2. Decreasing Concentration of Reactants:
* Collision Frequency: Higher reactant concentrations mean more molecules are present, increasing the chance of collisions between reactant molecules. Lowering concentrations reduces collision frequency, slowing down the reaction.
3. Increasing Activation Energy:
* Activation Energy Barrier: The activation energy is the minimum energy required for a reaction to occur. Increasing the activation energy barrier makes it harder for molecules to reach the necessary energy level, slowing down the reaction. This can be caused by:
* Introducing a catalyst that slows the reaction down (a negative catalyst).
* Changing the reaction medium (e.g., using a different solvent).
4. Increasing Surface Area:
* Heterogeneous Reactions: Reactions involving substances in different phases (e.g., solid and liquid) are affected by surface area. A larger surface area provides more contact points for the reactants, increasing the reaction rate. However, decreasing surface area reduces contact points, slowing down the reaction.
5. Adding a Catalyst that Slows the Reaction:
* Katalysatorer: While most catalysts speed up reactions, there are some that can act as negative catalysts and slow down reactions. These catalysts increase the activation energy, making it harder for the reaction to occur.
6. Changing the Phase of Reactants:
* Reaction Rates in Different Phases: Reactions tend to be faster in the gas phase compared to the liquid phase, and even slower in the solid phase. This is due to the increased freedom of movement and collision frequency in gases.
7. Increasing the Partial Pressure of Inert Gases:
* Collision Frequency: I en gasblandning minskar inerta gaser det partiella trycket hos reaktanter, vilket leder till färre kollisioner mellan reaktantmolekyler och minskar reaktionshastigheten.
8. Adding a Product to the Reaction Mixture:
* Le Chatelier's Principle: Enligt Le Chateliers princip förskjuter att en produkt till en reaktionsblandning förskjuter jämvikten mot reaktanterna och bromsar framåtreaktionen.
Exempel:
Imagine a campfire. Adding more wood (increasing concentration) and blowing on the fire (increasing temperature) will make it burn faster. Conversely, covering the fire with ash (decreasing surface area) and using wet wood (lowering temperature) will slow down the burning process.
