ScienceIQ.com

Look, Up in the Sky. It's A Bird. No It's A Meteorite!

Most folks probably think of swallows and the ringing of the Mission bells when the words San Juan Capistrano are heard or seen. This is a popular tradition that celebrates the return of cliff swallows as they migrate north from their winter home in Argentina to their spring and summer home in southern California. The swallows' return typically ...

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MeteoriteSky
Biology

Spiders and Their Venom

Spiders, which have been around for about 300 million years, are built differently from insects. They have eight legs, not six, and their bodies are divided into two sections, not three. Entomologists ... Continue reading

SpidersVenom
Astronomy

Large Asteroid Zooms Safely Past Earth

A mountain-sized asteroid made its closest approach to Earth at 9:35 a.m. Eastern Time on Wednesday, Sept. 29, 2004. Although asteroid 4179 Toutatis came no closer than four times the distance between ... Continue reading

LargeAsteroidZoomsPastEarth
Chemistry

Radon, A Rare Element

To the best of our knowledge, the entire universe is constructed from just over a hundred different types of building blocks called atoms. Each has its own characteristic properties, and while there ... Continue reading

RadonARareElement
Biology

Food Irradiation: A Safe Measure

Food safety is a subject of growing importance to consumers. One reason is the emergence of new types of harmful bacteria or evolving forms of older ones that can cause serious illness. A relatively ... Continue reading

FoodIrradiationASafeMeasure

Catalysts

CatalystsChemical reactions are interactions between atoms and molecules that result in a change in their relative arrangements and interconnections. The reaction affects only individual atoms and molecules, but even just a small mass of any material contains billions and billions of atoms or molecules. Just one gram of hydrogen gas, for example, contains about 602,235,900,000,000,000,000,000 hydrogen atoms! For an individual reaction to occur, electrons within atomic and molecular bonds must become 'activated' and enter a state that allows the required bonding changes to occur. This new intermediate or transitional state represents a higher energy state of the reacting atoms and molecules, and this poses a barrier to the progress of the individual reactions. Each individual reaction must overcome the 'activation energy' barrier as the overall reaction proceeds through the mass of reacting materials.

A catalyst is something that can interact with the reacting materials in such a way that the 'activation energy' barrier of the individual reactions becomes much lower. This usually occurs when reacting atoms or molecules adhere to the surface of the catalyst. The electrons of the affected molecules become partially rearranged in this association of catalyst and substrate, and in a way that is very favorable to the desired reaction. The association of catalyst and substrate is completely reversible. Once formed, the catalyst-substrate complex can dissociate in two ways: either they separate into their original unassociated forms, or they separate as the substrate completes its reaction transformation. In either case, the catalyst returns to its original form. So, while a catalyst becomes very intimately involved in the reaction process, it does not itself undergo a reaction, and is usually recovered intact after a reaction has gone to completion.

Perhaps the most readily known example of the application of a catalytic system is in the 'catalytic converter' of the typical automobile. It's purpose is to complete the combustion of gasoline residues coming from the engine. Under ideal conditions, gasoline would completely oxidized during combustion to produce mostly carbon dioxide and water. But in our less-than-ideal world, combustion is usually incomplete and the exhaust gases contain gasoline hydrocarbon molecules in various states of oxidation. These gases enter the catalytic converter where they pass through a dense honeycomb, with a very large surface area, coated with metals such as platinum or palladium that function very well as catalysts. Their atoms interact well with both hydrocarbons and oxygen, and in joining with the catalyst both become more reactive. When both are present on the catalytic surface, much less energy is needed to bring them into a reactive conformation, and reaction between them is made much easier.