according tosubjectThe specific reference of the concept of "matter" is different.In chemistry, a substance is anything that has a specific molecular identityOrganic matterOr inorganic substances, including: (1)chemical reactionAny compound of a substance produced as a result of or naturally occurring;(2) Any element or unconjugatedAtomic cluster。Chemical substances include elements, compounds (including additives and impurities), by-products and reactionsintermediateandpolymer。
Atoms are the smallest particles in chemical changes. In chemical reactions, atoms are reassembled into new substances.atomThroughChemical bondSyngenetic formationmolecule。IonsIt is a charged atom or atomic group.
1. Naturally Occurring Chemical Substance: refers to anynatural environmentRaw materials present in thedissolutionNot occurring in water, flotation, or dehydration by heatingChemical changeThe process of extracting any substance from the natural environment.
2. Well defined Chemical Substance: refers to the completeChemical structural formulaAnd a specific molecular formula, althoughSubstituentThe position of is unknown or variable, but the information such as the number of substituents is known.
3. Poorly defined Chemical Substance: refers to the chemical substance that cannot be used completelyChemical structureOr/and chemical substances described by specific molecular formula.
4. Existing Chemical Substance: refers to the chemical substances that are produced in China for commercial purposes or have been imported from abroad and listed in the List of Existing Chemical Substances in China during the legal period.
5. New Chemical Substance: refers to any chemical substance not included in the List of Existing Chemical Substances in China.
6. Research and development chemical substance: any chemical substance manufactured or imported for scientific research and development or analysis and testing only.[1]
Classification of chemical substances
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Chemical substance is not only the material undertaker of chemical movement, but also the material object of chemical science research.Although this material object is only represented by material molecules from the perspective of chemical objects, it has a variety of forms from the perspective of chemical content, involving many substances.Therefore, it is very important to study the classification of chemical substances.
According to the continuous and discontinuous (discrete) forms of substances, chemical substances can first be divided into substances of continuous macro morphology, such as various elementsSimple substanceAnd compounds, as well as discontinuous microscopic forms of substances - such as various chemical particles and other two categories of substances.
Cross classification: The same substance is classified according to different standards.For example:
, can be divided intosodium salt、anionThe angle is divided into sulfate ion.
Multidimensional classification: With the development of chemistry, new attempts are being made to classify chemical substances.Famous Chinese chemist, Peking UniversityXu GuangxianProfessor is committed to exploring a new classification of chemical substances, namely molecular classification or "multi-dimensional classification".In 1982, he proposed the (n × c π) four-dimensional classification of molecules and seven related structural rules at the Sino Japanese American Symposium on Metal Organic Chemistry.In the new classification, he proposed the concept of molecular slice.Molecular slice is an intermediate concept between atoms and molecules.For example:Sulfate radical、CarbonateAnd the functional groups of organic compounds can be regarded as molecular slices.Each molecule slice is composed of a central atom and a ligand.Using this molecular classification method, millions of organic and inorganic molecules can be regarded as each composed of several molecular slices.According to the four-dimensional classification method, all molecules are divided into four types, namely, single molecule, double molecule, multi molecule (including chain, ring, multi ring andCluster compound）And compound molecules (regarded as complex atoms formed by various combinations of chains, rings and clusters).The molecular slices that make up these molecules can be divided into 25 categories according to the number of valence electrons.For the same kind of molecular chips, they can also be further classified according to the different periods of their central atoms.In this way, all molecules can be classified by using the concept of molecular slice and four-dimensional classification and structural rules.At the same time, we can also estimate the molecular structure type from the molecular formula, and predict new cluster compounds andOrganometallic compoundAnd discuss their reactivity.[2]
Presence status
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There are six existing forms of matter: solid, liquid, gas, plasma, Bose Einstein condensateFermionic condensate 。Solid matter has shape and volume, and their molecules are tightly bound together.Liquid substances also have volume but no shape. In contrast, their molecules are loosely bound, so liquids can be dumped into a container to measure their volume.Gases have neither volume nor shape, and their molecules will move freely to fill any container that can close them.Plasma state is composed of equal amount of negatively charged electrons and positively charged ions.Bose Einstein condensate indicates that atoms in different states suddenly "condense" to the same state (generally the ground state).That is, atoms in different states "condense" to the same state.
Gaseous substance
Our living space is surrounded by a lot of gas.Many ancient people observed that the wind could bend the slender tree trunks, and bubbles would appear in the boiling water.Therefore, early philosophers believed that there was an element called "air" and it had a rising tendency.In the 17th century, Torricelli proved that air has the same weight as solid and liquid.In the 18th century, chemists proved that air was a mixture of various gases, and many gases were found in chemical reactions.These newly discovered gases have immediate practical applications. For example, the gas extracted from coal can generate light and heat.
Liquid substance
Liquid particles attract each other and are close to each other, so it is not easy to compress a fixed volume of liquid into a smaller volume or expand it into a larger volume.When heated, the distance between liquid particles usually increases, resulting in volume expansion.When the liquid is cooled, the opposite effect will occur and the volume will shrink.Liquid can dissolve some solids. For example, when salt is put into water, salt particles seem to disappear gradually.In fact, it is because salt dissolves in water, ionizes sodium ions and chloride ions, and distributes evenly in water to form an aqueous solution.In addition, liquids can also dissolve gases or other liquids.
Solid matter
Solid matter has a fixed shape, while liquid and gas do not.If you want to change the shape of a solid, you must apply force to it.For example, squeezing or stretching can change the volume of solids, but usually it will not change too much.Most solids will become liquid when heated to some extent, and will become gas if the temperature continues to rise.However, some solids will decompose after being heated, such as limestone.Crystal and metal are the two most important solids.
Plasma matter
When the gas is heated, when its atoms reach thousands or even tens of thousands of degrees Celsius, the electrons will be "thrown off" by the atoms, and the atoms will become only positively charged ions.At this time, the charge of electron and ion band is opposite, but the amount is equal. This state is called plasma state.Lightning, meteors and fluorescent lamps that people see all year round are in plasma state.Humans can use it to emit a lot of energy to generate high temperatures, cut metals, manufacture semiconductor components, and carry out special chemical reactions.In the boundless space, plasma is a universal state.The temperature and pressure inside most of the luminous stars in the universe are very high, and the matter inside these stars is almost in the plasma state.Most of the matter in the universe is in the plasma state, and solid, liquid and gas are the real rare material states.Only those dim planets and scattered interstellar matter can find solid, liquid and gaseous matter.
Bose Einstein condensed matter
Bose Einstein condensation (BEC) is a new state of matter predicted by Albert Einstein 70 years ago.The "condensation" here is different from the condensation in daily life. It means that atoms in different states suddenly "condense" to the same state (generally the ground state).That is, atoms in different states "condense" to the same state.
The discovery of this new fifth state has to be mentioned from 1924, when Bose, a young Indian physicist, sent Einstein a paper and proposed a new theory about atoms. In the traditional theory, people assume that all atoms (or molecules) in a system can be identified. We can name one atom Zhang San and the other Li Si,He would not recognize Zhang San as Li Si, nor would he recognize Li Si as Zhang San.However, Bose challenges the above assumption and believes that it is impossible to distinguish the difference between two atoms of the same kind (such as two oxygen atoms) on the atomic scale.
Bose's paper attracted Einstein's great attention. He applied Bose's theory to atomic gas, and then speculated that under normal temperature, atoms can be in any energy level (energy level means that the energy of atoms is arranged from low to high like a step), but at very low temperature, most atoms will suddenly fall to the lowest energy level,It's like a building collapsing suddenly.A large number of atoms in this state behave like a large super atom.For example, the scattered soldiers on the training ground suddenly received the command of the commander to "march forward", so they quickly gathered together and walked forward like a soldier.Later, the physical world called this state of matter Bose Einstein condensate (BEC), which means that atoms in different states suddenly "condense" to the same state.This is the new Bose Ericsson condensate.
According to the introduction of Deborah King, the head of the research group of "Fermion Condensate", "Fermion Condensate" and "Bose Einstein Condensate" are the forms of matter in the quantum state, but the matter in the "Fermion Condensate" is not a superconductor.
Quantum mechanics believes that particles can be divided into two categories according to their collective behavior at high density or low temperature: one is Fermion, named after Italian physicist Fermi;The other is boson, named after Indian physicist Bose.The difference between the properties of these two types of particles is most obvious at extremely low temperatures: bosons are all gathered in the same quantum state, while fermions are the opposite, more like“Individualist”, each occupies a different quantum state.“Bose Einstein condensate”Matter is composed of bosons, which act like a large super atom, while the "fermion condensate" matter uses fermions.When matter cools down, fermions gradually occupy the lowest energy state, but they are in different energy states, just like a crowd rushing to a narrow staircase. This state is called "fermion condensate".[2]
Representative
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Representative
mixture
It is composed of two or more substances (macro and micro).
Air, oil
Pure substance
What is composed of one substance is pure substance (macro).
Oxygen, iron
Simple substance
Pure substances composed of the same elements are called simple substances.
Diamond, oxygen, sulfur powder, copper
chemical compound
Pure substances composed of different elements are called compounds.
Potassium chlorate, ammonia, water
organic compound
Usually, carbonelementThe compounds are called organic compounds, or organics for short.
Any oxide that can react with alkali to form salt and water is called acid oxide.
Sulfur trioxide, carbon dioxide
Alkaline oxide
Any oxide that can react with acid to form salt and water is called alkaline oxide.
Sodium oxide, magnesium oxide
Orthosalt
The product of complete neutralization of acid and base.
calcium carbonate
Acid salt
The product of partial neutralization of hydrogen ions in acid.
Sodium bicarbonate, sodium dihydrogen phosphate
Basic salt
The product of partial neutralization of hydroxyl ion in alkali.
Basic copper carbonate
Reference material
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Reference material
Primary standard material is used for direct preparation in analytical chemistrystandard solution Or calibrationTitrimetric analysisA substance in the concentration of the operating solution.The definition of reference materials is more and more accurate, and the classification is clear, which plays an important role in many fields.
Reference Material (RM) - a material or substance with one or more sufficiently uniform and well determined characteristic values to calibrate measuring devices, evaluate measuring methods or assign values to materials.
Certified reference materials(Certified Reference Material, CRM) -- Reference material with certificate, one or more characteristic values of which are determined by the procedure with traceability established, so that they can be traced to the accurately reproducedUnit of measurement, each characteristic value given on the certificate is attached with a givenconfidence level OfUncertainty。
RM or CRM has different titles in different industries and fields in China.Metrologists usually call it "reference material" and adopt the definition consistent with the above ISO Guide-30 [4];The authors of standardization are more accustomed to calling it“Standard sample”(short for“Standard sample”）, and the following definitions are given in GB/T15000.2-1994 [5]:Standard sample(RM) - A batch of samples with one or more chemical, physical, biological, engineering or sensory properties that are sufficiently uniform, have passed technical appraisal, and are attached with relevant performance data certificates.CertifiedStandard sample(CRM) - refers to the standard sample with one or more performance characteristics, which has passed the technical appraisal, attached with the certificate describing the above performance characteristics, and approved by the national standardization management agency.
From the above definitions, they have both metrological characteristics and standardization connotation.As far as metallurgy, nonferrous metals and other industries are concerned, there is no essential difference between the two, and their English descriptions are the same (RM, CRM); for researchers, their development procedures are the same, and their internal quality requirements are the same;For users, their functions are the same or similar.What is different is that the management organization and application procedure are different, and the emphasis is slightly different.
Reference material requirements
It is a kind of chemically stable substance with high purity and composition highly consistent with its chemical formula (for example, Grade I or higher purity than Grade Ireagent）。
The reference material should meet the following requirements: ① composition and itschemical formulaStrict compliance.If there is crystal water, the content of crystal water should also conform to the chemical formula. ②The purity is high enough, the content of main components is above 99.9%, and the impurities do not affect the accuracy of titration reaction. ③Stable in nature.For example, it is not easy to absorb moisture in the air,carbon dioxideIt is not easy to be oxidized by oxygen in the air. ④When participating in the reaction, it shall be carried out quantitatively according to the reaction formula without occurrenceside reaction。⑤It is better to have largerMolar massWhen preparing the standard solution, you can weigh more to reduce therelative error。
