Can graphite become diamond? Are graphite and diamond the same substance?

Diamond and graphite can be transformed under certain conditions, and this transformation can be analyzed from the following aspects.

1 Characteristics of chemical change.

We know that chemical changes are often referred to as chemical reactions. A chemical change is a change in which other substances are produced when the change occurs. Substances are transformed into new substances that are completely different in nature through chemical reactions, which is the characteristic of chemical change.

When graphite, an element composed of carbon, becomes a diamond under certain conditions, although diamond is also a carbon element, the properties of diamond are very different from graphite (the chemical properties of graphite are more active than diamond); It is another elemental element of carbon. This shows that diamond is a new substance that is changed from graphite in the process of change. If there is a change in the formation of new matter, it is not a physical change.

2 Crystal structure.

When graphite is converted to diamond, the graphite crystal structure is destroyed; The weak bond between the middle layer of graphite and the layer is broken or changed, or at the same time, the chemical bonds and bonding methods between the carbon atoms on the hexagonal plane are "greatly changed and reorganized", so that the combination between them is regularly combined into a three-dimensional centric structure according to the form and requirements of diamond. That is, the layered structure of graphite is transformed into a regular tetrahedral structure of diamond. Based on the fact that there is only one structure of the same substance, graphite and diamond are two substances with different crystal structures.

Since the process of change is from one substance to another, it is not a physical change. It can be seen that the transformation of matter from one structure to another is a chemical change process.

3 Thermal effects.

When a chemical reaction is carried out, it is often accompanied by a change in energy, which can be in the form of light, electricity, mechanical or thermal energy, and often in the form of thermal energy, sometimes to release heat, sometimes to absorb heat. Diamond is heated to 1000 °C in isolation from air and can be converted into graphite

This transition is an exothermic reaction. It illustrates the conversion of energy into the form of heat when a chemical reaction occurs during this transition. When graphite becomes diamond, it is a chemical reaction that absorbs heat energy. Therefore, the transformation of graphite into diamond under certain conditions is not a physical change.

4 Catalysts.

The conversion of graphite into diamond must be carried out at high temperature and high pressure, and even at a temperature of 2000 4000 and a pressure of 6120,000 atmospheres, this conversion rate is still not large, and chromium, iron and platinum are used as catalysts. According to the principle that a catalyst can only change the rate of chemical reactions, a catalyst cannot change the rate of physical change. When graphite is converted to diamond, a catalyst is used to speed up the reaction rate.

If this transition is physical, wouldn't the use of catalysts be meaningless? It can be seen that this transition is not a physical change.

In summary, the interconversion of diamond and graphite under certain conditions is a chemical change. All interchanges of allotropes under certain conditions are chemical changes. Some people say that the mutual conversion of diamond and graphite under certain conditions is a physical change process, but this statement is incorrect.

The conversion of graphite to diamond should be a difficult reaction process.

Studying the thermochemical equation for the conversion of graphite into diamond is an endothermic process, and the enthalpy change is not large, about 40 kilojoules per mole. It seems like an easy reaction to make.

However, it must also be taken into account that during the chemical reaction, the reactants must reach the activated state, and the activated molecules can effectively collide with each other in order for the reaction to proceed. Activation energy is required to reach the activation state, and the activation energy required for graphite to be converted into diamond is very high, which cannot be satisfied by general reaction conditions. But it's not impossible, and a corresponding catalyst is needed.

By analogy, all kinds of reactions in the human body are catalyzed by enzymes, and each reaction seems to be a much easier reaction than common difficult reactions such as thermite, but it is a matter of activation energy, so enzymes are needed to catalyze and reduce the activation energy of the reaction to promote the reaction.

But if you can easily convert graphite into diamond, it's a great way to increase your GDP.

At present, more than a dozen countries in the world (including China) have synthesized diamonds.

However, because the particles of this kind of diamond are very fine, the main use is to make abrasives, drill bits for cutting, geology, and oil drilling. At present, 80% of the world's diamond consumption is mainly used in industry, and its output far exceeds the production of natural diamond.

The originally synthesized diamond particles are black, the size and weight of about carats (the minimum diamond used for gemstones is generally not less than carats).At present, the large-grain diamonds developed in China are more than 3mm, and the United States, Japan, etc. have made carat diamonds. We say that diamond has "flown out" from graphite, and gem-quality synthetic diamond will also be on the market in the near future.

It is not a rigid stone that can be used to cut glass and make drill bits, because it is very hard; Graphite can be used as a pencil lead, lubricant, because it is soft and creamy. According to the Mohs scale, diamond is the highest grade. Diamond is the hardest substance found naturally in nature.

Diamond and graphite are also made up of carbon atoms, and why diamond is so hard depends on its molecular structure.

The figure below is a structural model of diamond. Each carbon atom is tightly bound to the surrounding 4 carbon atoms through strong interactions. The distance between the two carbon atoms that are "tightly bonded" is approximate, resulting in a dense three-dimensional structure that makes diamond the hardest substance that occurs naturally.

Graphite, on the other hand, has a layered structure, and in the case of a sheet, every 1 carbon atom will be tightly bound to the 3 carbon atoms around it through strong interactions, and the distance between the two carbon atoms that are "tightly bonded" is approximately. In graphite, the distance between the layers is that because the distance is relatively large, the interaction of carbon atoms is weak, so it is easy to slide and crack in the direction parallel to the layer, so the graphite is very soft and slippery.

Diamond is denser in structure than graphite. The density of diamond is about twice that of graphite (the density of diamond is about, the density of graphite is about.

When carbon atoms are tightly bound together by strong interactions (chemical bonds), the smaller the distance between the atoms, the stronger the interaction. In a sheet of graphite, the distance between carbon atoms is smaller than that of diamond, the interaction is stronger, and it is more difficult to be destroyed, so graphite has a higher melting point.

As shown in the table below, diamond and graphite have different melting points but the same boiling points, why is that? There is a certain relationship between the change of the state of matter and the distance between the particles. After the melting of graphite and diamond, the original arrangement of carbon atoms is broken, the distance between the atoms is equal, and the interaction strength is the same, so the boiling point is the same.

We all know that graphite is electrically conductive. This is also closely related to the structure of graphite. The outermost shell of a carbon atom has 4 electrons, and in a sheet of graphite, each carbon atom forms a strong interaction (chemical bond) with the 3 carbon atoms around it by "sharing electron pairs", and each carbon atom has only 3 outermost electrons involved in the formation of this "force", so that there is only 1 free electron left.

Because there are a large number of free electrons present, graphite can conduct electricity. Each carbon atom in diamond and its surrounding 4 carbon atoms form a strong interaction through "shared electron pairs", and almost all the outermost 4 electrons of the carbon atom participate in the formation of this "force", and there are basically no free electrons, so they basically do not conduct electricity.

Structure can determine properties, diamond and graphite are both made of carbon atoms, but because of the different arrangement of atoms, many physical properties are very different.

Graphite and diamond are not the same kind of substances, they belong to allotropes, although they are composed of the same chemical element, but the different composition and structure lead to different physical properties, and their physical properties are very different.

This one is wrong. They are allotropic forms of each other. They are all elemental elements composed of carbon elements. But not the same substance.

Changing the arrangement of atoms at high temperature and pressure can turn graphite into diamond. That is, graphite can be converted into diamond at a pressure of 5-60,000 atmospheres ((5-6) 103MPa) and a high temperature of 1000 to 2000 degrees Celsius.

Both diamond and graphite have a chemical composition of carbon (C), called "allotropes". From this designation, it can be known that they have the same "quality", but the "shape" or "nature" is different, and there is a world of difference, diamond is the hardest substance at present, while graphite is one of the softest substances. Graphite can be turned into diamond under high temperature and high pressure, but it cannot become diamond just by absorbing heat.

In 1938, the scholar Rossini laid the theoretical foundation for synthetic diamond through thermodynamic calculations, and calculated that in order to turn graphite into diamond, it was possible to at least 15,000 atmospheres and 1,500 degrees Celsius under high temperature conditions, and in the 50s and 60s, instruments and devices that could achieve the above conditions were built.

Expand Zixiang back bulk materials:

Graphite characteristics: Graphite is an allotrope of the element carbon, and each carbon atom is surrounded by three other carbon atoms (arranged in a honeycomb-like hexagon) to form a covalent bond.

Since each carbon atom emits an electron, which can move freely, graphite is a conductor of electricity. Graphite is one of the softest minerals, and its uses include the manufacture of pencil leads and lubricants. Carbon is a non-metallic element that is located in the second period of the periodic table, group iva.

Diamond Qualities:

Diamond is an elemental crystal composed of carbon elements formed under high pressure and high temperature conditions in the deep part of the earth, which refers to diamond that has been polished. Diamond is a colorless octahedral crystal, its composition is pure carbon, which is linked by carbon atoms with tetravalent bonds, and is the hardest substance known to exist in nature. Because the C-C bond in diamond is very strong, all valence electrons are involved in the formation of covalent bonds, there are no free electrons, so diamond hardness is very large, the melting point is 6900 degrees Fahrenheit, diamond has a ignition point of 720 800 in pure oxygen and 850 1000 in air, and it does not conduct electricity.

The only way to judge physical and chemical changes is whether new substances are formed. Where there is a new substance, it is a chemical change, and there is no new substance that produces a physical change.

Both graphite and diamond are made up of carbon. However, graphite is a layered structure, and the carbon atoms in each layer form a regular hexagon, and the layers are connected by van der Waals forces;

Diamond is a tetrahedral structure, and each carbon atom is connected together by covalent bonds, and its performance is very stable. Both substances are allotropes of carbon, and although they are both composed of carbon, their structures are completely different, so they are not the same substance.

Therefore, the transformation of graphite into diamond is a chemical change rather than a physical change.

At present, there are two ways to turn Li Xiao's graphite into diamond:

1. Put graphite at 5 to 60,000 units of atmospheric pressure and 1000 degrees Celsius high temperature, and then use metallic iron, cobalt, nickel, etc. as catalysts to convert graphite into diamond.

2. Graphite is heated by laser and then prepared by carbon dioxide reduction method.

Graphite: An allotrope of elemental carbon, which is softer and can be used to make pencil leads and lubricants.

Diamond: A mineral composed of the element carbon, which is an allotrope of the element carbon and the hardest substance naturally occurring in nature.