My Science School

The discovery of copper opened up new possibilities for humans. Copper exists in nature in the shape of nuggets. Gold and silver occur in the same shape, but they are very rare. Copper on the other hand is widely distributed and readily available.

Copper can easily be worked into different shapes. This was the reason why copper was preferred by the early humans. It was easy to make tools and weapons out of copper and they lasted longer than those made out of stone. They were much lighter than the stone toots as well. Moreover, copper tools could be sharpened again and again, so that they remained as good as new.

Early humans started with learning to extract copper from ores. Later their technology advanced; they began mixing copper with zinc to create an alloy called bronze, thus ushering a period known as the Bronze Age. 

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Alloys can be broadly classified into two groups based on their iron content- ferrous and non-ferrous alloys.

The base metal for some alloys is iron and they are known as ferrous alloys. Carbon steel, alloy steel, stainless steel, tool steels and cast iron are a few examples of ferrous alloys. Alloys that do not contain any iron are called non-ferrous alloys. Out of non-ferrous alloys, there are a large number of copper alloys. Most copper alloys are brasses and bronzes. Most kinds of brass can easily be shaped and have a pleasing appearance.

Other non-ferrous alloys include alloys of aluminium, titanium, zinc, nickel, cobalt, tungsten, precious metals, and refractory metals. They have a wide range of applications ranging from construction work to the manufacturing of medical equipment.

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Steel is an alloy and it is obtained by mixing iron with carbon and some other elements. But steel can be further combined with other elements to obtain alloy steel. Alloy steels have a wide range of uses.

Stainless steel is one of the most popular and renowned alloy steels; it contains chromium, nickel and manganese. It is hard and strong, and resists heat and corrosion. Therefore stainless steel is used to make a wide range of objects ranging from cutlery and cookware to lifts and subway trains, from safety pins and furniture to car engines and chemical plants.

Manganese alloy steels are used to make rock crushers, power shovels and other machines, which have to be extremely tough and strong. Carbon steel is used for building bridges, cutting tools and high strength wire.

Some of you might know the periodic table. Others might have at least heard of this amazing table, which is nothing but an arrangement of elements according to their atomic number, electronic configuration and chemical properties.

Transition metals are a group of metals found in the middle of the periodic table. These metals serve as a bridge between the elements on both sides of the periodic table. The term ‘transition metal’ was coined in 1921. Zinc and manganese are transition metals.

Transition metals share some general properties. They are malleable and ductile, and they conduct heat and electricity. Though there are similarities, these metals vary a great deal from each other. For instance, tungsten is a transition metal and it has the highest melting point out of all metals. On the other hand, mercury, another transition metal exists in liquid state at room temperature.

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An alloy is made by mixing two or more chemical elements, out of which at least one element is a metal. Brasses, steel and bronze are some of the most commonly used alloys in our daily life.

Alloys will have qualities that are different from that of the metals used to make them. Generally, alloys are harder and stronger than the metals they are made of. Alloying also makes it possible to create materials with just the right combination of properties that we need for a particular purpose.

For example, by combining aluminium with copper, magnesium and other metals, you get an alloy that is light yet strong enough to be used for building aeroplanes. Similarly, steel is a very useful alloy that is used in making everything from skyscrapers to saucepans! Half of today’s utensils would not be present if not for steel.

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According to the differences in properties, metals can be further classified into different groups - actinide metals, lanthanide metals, alkali metals, alkaline-earth metals, noble metals, rare metals, and transition metals.

Actinides are radioactive metals and do not generally occur in nature. The metals that are light in weight and shiny come under alkaline metals. Transition metals are generally coloured and are good conductors of heat and electricity. Scandium and titanium are transition metals.

Noble metals do not corrode easily and exist in their natural state on Earth. They resist chemical action and cannot be easily attacked by acids. Gold and platinum are noble metals.

In contrast, lanthanides tarnish quickly. They are silvery-white in colour and are also known as rare-earth metals. Europium is a lanthanide.

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When you look at the shiny surface of a metal like gold, you will feel that it is smooth and even throughout. But in reality, it is not so. Metals appear to have a smooth surface because they are polished.

All solid metals are made up of crystals so small that they cannot be seen by the naked eye. When we polish a metal, the atoms spread on its surface just like butter on a slice of bread. This is why the metal appears smooth. If the surface layer is scraped away, the small crystals, which make up the metal, can be clearly seen under a microscope.

In addition to this, pure metals are either too soft or brittle and are chemically reactive for use. Hence they are often combined with several other substances in different ratios to modify them for our use.

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By now, we have some knowledge of metallurgy. The Industrial Revolution that took place in the 18th century changed the way in which metals were used so far.

Significant advancements took place in the fields of metal extraction and processing. Thanks to the invention of steam power and electric power, it was possible to have big machines that could make thousands of metal parts in a short time.

Till the Middle Ages, humans knew only seven metals. In fact, right up to the Industrial Revolution, only nine metals were known to humans - gold, copper, silver, lead, tin, iron, mercury, bismuth and antimony.

The invention of the electric battery led to the discovery of a process known as electrolysis by which electric current is passed through a substance to effect a chemical change. Electrolysis led to the discovery of many new metals, like magnesium and aluminium.

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The Bronze Age was followed by the Iron Age. Meteorites that fell on Earth contained traces of iron and it is from these fallen rocks that early humans came to know about iron. But meteorites rarely fell on Earth and iron was not a common metal for a long time.

Humans did not learn to use iron properly up until 1900 BC. Iron was hard to deal with; it is hard to make tools with, for it melts at a higher temperature than bronze. After humans learnt the technique of smelting iron and moulding it into different shapes, iron became popular. Many tools and weapons were then made out of iron.

Iron replaced bronze for a number of reasons. Iron ores were more readily available; the ore was simply smelted or heated in a coal fire, the pieces of iron were picked out, re-heated into a single lump, and then hammered into the required shape. There was no need for iron to be alloyed either.

You might have heard of the term Bronze Age in your history text books. Bronze is an alloy; it is a mixture of tin and copper which is harder and more durable than pure copper or tin. But why is a period known by the name of an alloy?

The Bronze Age began when early humans learnt to mix tin and copper to make bronze. The period between 3500 BC and 1200 BC is known as Bronze Age. It began in the present-day regions of Turkey, Iran, and Iraq, which were also the cradles of human civilization.

During this time, bronze was the most important metal for making tools and weapons, and the properties of bronze made it possible to make tools more and more sophisticated. Bronze made possible some of the significant advancements in human history.

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You might have heard of the term Bronze Age in your history text books. Bronze is an alloy; it is a mixture of tin and copper which is harder and more durable than pure copper or tin. But why is a period known by the name of an alloy?

The Bronze Age began when early humans learnt to mix tin and copper to make bronze. The period between 3500 BC and 1200 BC is known as Bronze Age. It began in the present-day regions of Turkey, Iran, and Iraq, which were also the cradles of human civilization.

During this time, bronze was the most important metal for making tools and weapons, and the properties of bronze made it possible to make tools more and more sophisticated. Bronze made possible some of the significant advancements in human history.

Metallurgy is a branch of science that deals with metals. It studies the physical and chemical properties of metals, their mixtures and compounds. In short, it is about the science and technology of metals. Metallurgy concerns with the production of metallic components for our use. It also deals with the purification of metals and the production of alloys.

Georgius Agricola is known as the ‘father of modern metallurgy’. He was a German scientist who developed various techniques to process metals.

Metallurgy can be broadly divided into three categories. Extraction metallurgy deals with the extraction of metals from ores and their refining. Several substances are added to the ores and they go through several stages of purification. Physical metallurgy is the study of the structure and properties of metals. Production metallurgy deals with the fashioning of metals into finished products.

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Many of the metals are not found in their pure metallic form in nature. When a metal is found in nature in its pure form, it is known as being in the Free State. On rare occasions, some metals like gold and silver are found in their pure form and can be used without much processing. But a majority of metals are hidden inside lumps that look like rocks. These rocks contain metals mixed with minerals.

Metals are often found in a mix of crystals of elements. The rocks which have minerals mixed with metals are known as ores. The ores have to be processed in several stages to obtain metals that are ready for use.

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          Metals can be differentiated from non-metals from their appearance. Metals are lustrous while non-metals are not shiny. Most of the metals are flexible and malleable. This means that metals can be stretched into sheets. Non-metals on the other hand are hard and brittle. While metals are good conductors of electricity and heat, non-metals do not conduct either electricity or heat in normal conditions.

          Apart from metals and non-metals, there is a third category known as metalloids or semi metals. These elements have the properties of both metals and non-metals. They are good conductors of heat and electricity, but they are not strong or workable like real metals. Carbon and silicon are metalloids.

Just take a look around your house and you will surely find at least ten items made of metal. Your house keys, car, gold ornaments, some of the utensils in the kitchen...the list will go on and on. We now know some of the uses of metals. But what are metals?

Metals are opaque, lustrous elements that are good conductors of heat and electricity. There are more than 100 chemical elements, and most of them are metals. These elements are hard, strong and are good conductors of heat and electricity. Metals can be made into useful shapes without breaking or cracking. Some metals are light while some others are heavy. They can combine with oxygen and other non-metals as well.

Metals are an important part of the modern world. They are present everywhere, ranging from safety pins to spacecraft. Our life would have been so different if we did not have metals.

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