Catalysts

Catalysts are substances that speed up chemical reactions but remain chemically unchanged at the end of the reaction.
They provide an alternative reaction pathway with a lower activation energy, allowing the reaction to proceed more quickly.
Catalysts are specific to certain reactions. This means that a catalyst that works for one reaction may not work for another.
Enzymes are biological catalysts. They speed up reactions in living organisms.
Catalysts can be either heterogeneous or homogeneous. Heterogeneous catalysts are in a different phase (solid, liquid, gas) to the reactants, while homogeneous catalysts are in the same phase.
Commercially, catalysts are important in many industrial processes, such as the conversion of nitrogen and hydrogen into ammonia (the Haber process) or the cracking of hydrocarbons in the petroleum industry.
Using a catalyst can result in significant cost savings in industrial processes, as they allow reactions to take place at lower temperatures and pressures.
The use of catalysts can also be environmentally beneficial, as they can help to reduce energy usage and the production of harmful by-products.
However, catalysts can be poisoned by impurities, which bind to the catalyst and prevent it from working. This means they need to be regularly cleaned or replaced.
The use of catalytic converters in vehicles helps to reduce the amount of harmful gases released into the atmosphere. The converter contains catalysts that speed up the reaction of these gases to produce less harmful substances.