Why molecules react with one another forms the basis of chemistry, biology and increasingly engineering. Kinetics vs. Thermodynamics: The Science Behind Chemical Reactions often think of the result: new products formed from reactants. In this blog post, will dig deeper into the science behind this process, looking more specifically at the role of kinetics vs. thermodynamics.
What Triggers a Chemical Reaction?
We call that a chemical reaction when molecules meet and rearrange to create new substances. However not all molecules react, and some conditions will determine whether or how fast a reaction will occur. Two big factors determine these conditions:
Thermodynamics — Indicates if a reaction is feasible.
Kinetics — Specifies how fast a reaction can wear away.
Knowing these concepts can also help explain why food rots faster in summer or firecrackers burst instantly, among other questions.
Thermodynamics: Will a Reaction Happen?
Thermodynamics is the study of the changes in energy within a chemical system. A reaction is thermodynamically spontaneous if it lowers the free energy of the system. Here are the key concepts:
Enthalpy (ΔH): This is the measure of the heat absorbed or evolved during a reaction. Reactions that release heat (“exothermic”) are generally preferred.
Entropy (ΔS): A measure of disorder or randomness in a system. The natural world tends to encourage those processes that tend towards entropy.
Gibbs Free Energy (ΔG): A measure encompassing enthalpy and entropy, used to ascertain a reaction's spontaneity. The formula is:
ΔG = ΔH – TΔS
A reaction is thermodynamically favourable if ΔG is negative.
Example:
Cooking food involves a combination of energy inputs (ΔH) and changes in molecular arrangements (ΔS), making the process thermodynamically favourable when heat is applied.
Kinetics: How Fast Does a Reaction Happen?
Yet even if a reaction is thermodynamically favourable, it won’t occur unless the molecules have sufficient energy to overcome the activation barrier. Kinetics deals with how fast a reaction happens, which is influenced by:
Activation Energy (Eₚ): The minimum energy needed for reactants to form products. This lower activation energy results in faster reactions.
Temperature:Â Higher temperatures give the molecules more energy (increased kinetic energy) and make collision which leads to a reaction more likely.
Catalysts: (lower the activation energy and speed up reactions without being consumed)
Example:
The Indian monsoon gets iron rusting in far more quantity owing to higher moisture (water availability) and temperature which portrays the effect of kinetics on reaction rates.
Applications
Fertilizers are chemicals with properties that help them interact with soil nutrients. Understanding these reactions can help us use fertilizer more efficiently.
Pharmaceuticals: Medicines are developed through known chemical reactions that are controlled via kinetics and thermodynamics.
Industry: Whether it’s creating steel or fabric, chemical reactions centre around India’s industrialization.
Daily Life:Â Chemical reactions are part of cooking, cleaning and even breathing. The process behind dosa batter preparation is an example of how microbial kinetics plays a role.
FAQs
What really is the difference between kinetics and thermodynamics?
Thermodynamics tells if the reaction is possible, and kinetics tells how to go fast.
Why do certain reactions require a catalyst?
Catalysts decrease the activation energy, and speed up the reaction but do not affect the overall thermodynamics.
Where can I find thermodynamics and kinetics in your day?
An example of this is the rusting of iron (low kinetics) and cooking food (high kinetics and heat involved).