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BIG ENCYCLOPEDIA FOR CHILDREN AND ADULTS
What is copper? Detailed answer
Directory / Big encyclopedia. Questions for quiz and self-education Did you know? What is copper? Man discovered copper before all other metals with the exception of gold. Even in prehistoric times, copper was used by people of the Stone Age. Copper is found in a fairly pure state - in nuggets and grains of metal without impurities. Perhaps for the first time, a person picked up these nuggets from the ground because they were beautiful. Then man made the great discovery that these strange reddish pebbles could be molded into any shape. It was a simpler method of making weapons and knives than flint chipping. A lot of time passed, and already other people found out that they could melt red stones and make cups and jugs from the molten mass. Then people began to mine copper and make all kinds of devices and utensils from it. For thousands of years, copper remained the only workable metal, as gold was not only too rare to be taken into account, but also too soft for practical purposes. Copper tools were probably used as early as the construction of the great Egyptian pyramids. When bronze (an alloy of copper and tin) was discovered, even more copper began to be mined. But after the discovery of iron, copper began to be used in small quantities, mainly by peoples at a low stage of civilization, until the era of electricity came. Since copper is a good conductor of electricity, it is widely used in modern industry. Very few have seen pure copper and are unlikely to recognize it if they see it. It is a lustrous, silvery substance with a slight pinkish tint that turns reddish as it comes into contact with air. The copper we usually see is reddish brown. This is the color of copper oxide, which is formed as a result of the interaction of the metal with air. Most of the world's copper exists in combination with other substances from which it must be separated before use. Often it is adjacent to sulfurous substances, which can also be combined with iron and arsenic, which makes it difficult to purify copper. Copper has some other virtues besides the fact that it has outlasted many other metals. It has high strength, but is nevertheless ductile enough to be drawn and shaped into any shape by machining. It conducts heat as well as electricity. Copper can be carved and engraved. But it's not easy to break. In addition, alloys such as bronze and brass can be created from it by combining it with other metals. Author: Likum A.
Who flew the first kite? The history of kites is so long that no one today will undertake to name the author of the first kite, or at least the country where he lived. Some argue that it was a Greek named Arkitas who lived in the XNUMXth century AD. e. But in the countries of the East, kites were launched, probably, long before that. In China, "snakes" have always been an important part of many holidays. On the ninth day of the ninth month of the Chinese calendar, the "High Flying Festival" is celebrated nationwide. The sky has a colorful view, completely dotted with snakes of various shapes and sizes. Some of them are shaped like fish, frogs, birds. This is not only a children's holiday: quite adult people unite in games. There are even "kite battles" in which kites with pieces of glass attached to them are used to cut the strings of other kites! In Western countries, snakes were used for more serious purposes. In 1752, Benjamin Franklin launched a silk kite into a thunderstorm to prove that lightning and electricity were one and the same. Even before Franklin, kites were flown with thermometers attached to them to study cloud temperatures. By the end of the 1,6th century, kites were used by most weather stations. They were equipped with devices for recording air temperature and humidity, wind speed. Some of these kites have flown over six kilometers! In order to reach such a height, not one, but several kites connected together were used. The snake thread was made of very thin wire and was so light that it weighed only 7 kg for 110 km, and strong enough to lift XNUMX kg without breaking. Before the invention of the airplane, kites were also used for military purposes, when balloons made forced landings due to strong winds. For example, one of these kites reached a length of 11 meters and lifted a person into the air by 30 meters. Although most kites are of the familiar triangular shape, the most powerful kites are box-shaped, completely closed at the top and bottom and partly at the sides. To build a kite in the form of a butterfly, a ship or a bird, one simply takes a greater number of sticks than in ordinary kites and pulls on the threads to obtain the desired shape.
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