My Science School

One of the most puzzling questions in science is about the extinction of dinosaurs. The most accepted answers for this puzzle points at the ‘asteroid disaster’ theory according to which a huge asteroid struck the Earth’s surface about 65 million years ago.

The exploding asteroid threw enormous amounts of dust into the air that blocked sunlight for more than a year. As a result, plants on the Earth’s surface died; the dinosaurs that lived on those plants as well as and the meat-eating dinosaurs that lived off the plant eaters, died.

But, how is it possible to know if an asteroid really did hit the Earth’s surface 65 million years ago? Scientists today have an answer to this. They have found a layer of the Earth’s crust that contains an unusually high level of iridium metal.

Iridium rarely occurs on Earth. But it occurs much more commonly in meteors and asteroids. Scientists believe the iridium-rich layer was formed when the asteroid struck the Earth’s surface. This ‘iridium clue’ is a key, therefore, to understanding how dinosaurs disappeared from the Earth.

There are millions of cars on our roads, and each one is a source of air pollution. We are aware of the issues caused by pollution from these vehicles, especially in the cities.

To reduce the problem of pollution, manufacturers have made many improvements to car engines and fuel systems. One of these changes came about in 1975 with an interesting device called a catalytic converter.

A catalytic converter is a stainless steel can with a catalyst made of platinum, rhodium and palladium alloys inside. The job of the catalytic convertor is to convert harmful pollutants into less harmful emissions before they leave the car’s exhaust system.

The catalytic converter has a honeycomb surface coated with the catalyst, which converts the polluting gases into less harmful nitrogen, carbon dioxide and water vapour.

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A group of six metals - ruthenium, rhodium, palladium, osmium, iridium, and platinum-are known as the platinum group of metals or PGM. The group is called by this name because platinum is found more than the others though all of them are very rare.

The platinum groups of metals have physical, chemical and anatomical similarities. They are dense, stable and are often recycled to have longer lives. The group has a variety of highly specialized uses.

Platinum is a silvery white metal that is more expensive than gold. It is used to make jewellery. Platinum and palladium are often used as catalysts. Iridium and rhodium are harder and have a lot of alloying applications. There are very few minerals containing the platinum group of metals, and they are found mainly in South Africa and Russia.

No one knew of the dangers radium posed when it was produced for the first time. Radium had an aura of mystery which attracted people. Moreover, people were fascinated by how it glowed when mixed with phosphor. No wonder, industries sprang up to manufacture hundreds of consumer products containing radium.

The health hazard caused by this fascinating new element was identified only later. The harmful effects of radium such as skin burns and hair loss were observed among early experimenters. Many of them died as a result of their work.

The widespread use of radium was later halted for health and safety reasons. But, its wide use in luminescent paints continued through World War II. The soft glow of radium’s luminescence made aircraft dials, gauges and other instruments visible to their operators at night.

Radium was also an early radiation source for cancer treatment. Small radioactive seeds were implanted in tumours to kill cancerous cells. Safer and more effective radiation sources are used today.

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The discovery of radium is one of the most interesting stories in science. The story begins with the research of the French physicist Antoine-Henri Becquerel of the ore called pitchblende containing the element uranium. Becquerel found that pitchblende gives off radiation.

Becquerel’s discovery caused great excitement among scientists. Many physicists stopped their own research and began to study this novelty. A scientist couple Marie and Pierre Curie were especially interested in pitchblende.

Eventually, they isolated a new element that gave off more intense radiation than pitchblende itself. The Curies named this new element polonium. That was not the end. They believed that there would be at least one other element in the pitchblende.

The couple continued with their studies and in 1898, they isolated a second new element- radium. Radium gave away intense radiations and it took the Curies another four years to prepare one gram of the element. To do so, they had to sift through more than seven metric tons of pitchblende!

Picture Credit : Google