Melting point of gold. Melting and boiling point of metals

It is the physical properties of metals, for the most part, that determine the areas of their application by people in engineering and industry. Among the main characteristics, the melting point is of no small importance. Knowledge of this parameter allows you to successfully combine various ingredients and create comfortable, strong and high quality alloys that are most suitable for household use.

Melting and boiling point of metals

For each representative this indicator is different. However, the limit of heating is for all metals. At a certain temperature, they begin to melt, passing from a solid to a liquid state. If you bring the indicator to a critical value, the metal will go to a gaseous state, that is, the process of boiling and evaporation will begin.

Therefore, there is an entire classification reflecting the ability of metals to melt. All of them are divided into the following groups.

1. Easy-melting. This group includes those that melt when measured below 600 ° C. Example: zinc, sodium, gallium, bismuth, tin, cesium and others.

2. Medium melting. The index is in the range of 600-1600 ^o C. For example, the melting point of gold in its pure form is 1063 ^o C, which means that it belongs to this group of metals.
3. Refractory. Over 1600 ^o C. Examples: titanium, tungsten, chromium and others.

It should be noted that this classification is valid only for pure metals. When it comes to alloys, the numbers change drastically, and the values may differ greatly from the baseline values.

The boiling point of metals is much higher than the parameter considered. So, if the melting point of gold is 1063 ° C, then boiling is already 2947 ° C. The difference is almost twice!

Gold: General Characteristics

Aurum, or gold, is a chemical element at number 79 in the periodic system. The atomic mass is 196,967 units. It is located in group I, an auxiliary subgroup. Refers to noble metals, along with:

• Platinum;
• Silver;
• Palladium.

From the point of view of chemical activity it is practically inert, without special conditions in the reaction does not enter. It has special physical properties that allow it to be used in jewelry, engineering, and industry.

Physical properties of gold

What is so unique about this metal that people have been chasing after centuries and who has become a symbol of financial prosperity all over the world?

1. Colour. For pure gold is characterized by a beautiful rich yellow color with a pronounced metallic luster. The liquid metal has a pale green color. Pairs of its yellow-green color.
2. Hardness. By this parameter, gold is inferior to many other representatives, since it is a soft metal. On the scale of hardness of substances (Mohs scale), this figure is 2.5-3.
3. The melting point of gold is 1063 ° C.
4. Conductivity is good, is 75% with respect to copper as a superconductor.
5. Thermal conductivity and heat capacity are also excellent. Products from gold instantly heated and also quickly heated.

Special properties that give gold a high value, we will consider separately. It:

• ductility;
• plastic;
• density.

Density of metal

The very characteristic of density means the weight of a substance per unit volume. So gold has almost the maximum value for this parameter. So, for example, half a glass of pure golden sand will have a weight of about 1000 grams.

The density of gold, free of impurities, is 19.3 g / cm ³ . If we talk about natural gold-bearing rocks, then the figure is somewhat lower - 18-18.2 g / cm ³ . This index makes it convenient to extract the metal in question from rocks. He also makes gold so expensive for a very small amount of grams.

Kovkost and plasticity

The melting point of gold, as well as its extreme malleability and plasticity make it convenient and obedient in the hands of experienced people. So, on hearing the concept of "gold leaf". What it is? It is rolled into the finest translucent sheets of gold pieces that do not lose their bright and beautiful luster. With gold leaf you can cover the surfaces of products, walls, domes of churches and so on.

Only 1 g of this amazing metal can produce a very thin wire, the length of which is almost 3 thousand meters! Gold is easily subjected to the following deformations without loss of properties and integrity of the structure:

• Squeezing;
• Crushing;
• Curvature;
• Grinding;
• rolling;
• Stretching;
• Giving any desired shape.

Naturally, such a set of physical properties can not remain unnoticed by humans, and therefore gold finds application in the most diverse branches of science, technology and industry.

Being in nature and using man

In its pristine form, gold is found in nature in the form of ingots, sand, or inclusions in rocks. Gold placers are the places of their extraction by man. In a mixture with sand, clay and other parts, it is removed, and then it is separated in its pure form.

Also, gold is contained in:

• Plants;
• Animals;
• The human body;
• Underground waters;
• Seas and oceans;
• Lithosphere.

Of all these places, people have learned to extract metal for use in their own needs. What is it for?

1. The most important branch is, of course, jewelry. Beautiful ornaments made from different alloys of gold are the main sign of the financial assets of almost every woman. They are given to loved ones, they invest money, admire them and appreciate them.
2. Equipment. The melting point of gold and platinum, as well as palladium, nickel and some other metals makes them very valuable for technical use. And the property of gold to possess a high degree of malleability and plasticity in combination with chemical inertness makes it possible to use a wire made of this metal in the smallest details, chips. For example, telephones, televisions, calculators and other electronic devices.
3. Gold is a hard currency around the world, which never depreciates. He is not afraid of inflation and default, so many keep their savings in ingots of this metal.
4. Awards for achievements in different sports, tournaments and games are executed from gold, silver and bronze, which once again highlights their high value.

Alloy Gold

The listed characteristics of metal in pure form make it not only unique and popular, but also affect the quality of products. So, due to the high softness, jewelry made of pure gold is easy to deform, crumple and spoil. Therefore, metal alloys with other representatives of the periodic system are most often used.

1. Gold of 585 tests. This alloy is the most sold and distributed in our country and abroad. What does it consist of? 58.5% - pure gold, 34% accounted for copper, 7.5% - silver. The melting point of gold of 585 tests is approximately 840 ^о С, which is much lower than that of the pure sample. However, in general, the properties of the alloy are much better, since impurities compensate for the shortcomings of simple metal. Copper serves to increase the strength and hardness of the product. However, if it is too much, the product will quickly undergo corrosion. Silver affects the color. Thanks to him, the alloy is more yellow, shiny, without the admixture of a green shade. The fact that the melting point of gold of 585 tests is so low in comparison with the pure variant indicates that it is necessary to handle products with extreme caution and care and not leave them near an open flame.
2. Gold 999. This alloy - on the basis of almost pure metal with a small fraction of copper. Because of this, the melting point of gold 999 increases in comparison with the previous index. It is 1063 ° C, that is, the same value as for a simple substance. Products made from such an alloy are softer, deformable, and therefore require careful handling and special care.

Gold 375

The melting point of gold 585 is the average. After all, there is still an alloy in which the share of precious metal accounts for only 37.5% (375 test). In such an option, the melting index generally approaches 770 ° C, which is the minimum value.

If we talk about an alloy based on gold and silver, then such options are not used at all. The product is too soft. Therefore, copper is mandatory. The melting point of silver and gold is approximately the same, the spread is small. In white metal, it is 961.8 ^o C. Therefore, their joint alloy does not greatly reduce the overall index in the product.

What determines the color of jewelry from gold?

What color the ornament will cast in the light, depends on what additives are in the mixture and what is their percentage ratio. A red tint will have a product in which 50/50 gold and copper-silver.

White - if palladium, nickel and more silver are added to the mixture. Green - silver and copper, pink - silver, palladium and copper.