1. What is chemistry?
Chemistry is a practical and creative science, a science that makes human life better, and a central science that meets the needs of society. The interaction, mutual penetration, mutual promotion and mutual synthesis between chemistry and other disciplines not only promote the development of chemical research and chemical theory, but also promote and promote the development of other natural sciences such as mathematics, physics, biology, astronomy, geology and materials science. So, what is the object of chemical research?
Everything in nature, from celestial bodies, planets to microorganisms, whether inanimate or living, is composed of various chemical elements. Different substances have different compositions and structures, so they have different properties. Chemistry is a science that studies the composition, structure, properties, applications and mutual transformation of substances at the atomic and molecular levels.
Second, the formation and development of chemical science
1, the emergence of ancient chemistry
Fire is the earliest chemical phenomenon that human beings come into contact with. The discovery and utilization of fire opened the door for chemical operation. The use of fire produced practical knowledge of chemical technology, combined with human thinking on the origin of all things (ancient Greek philosophy and eastern mysticism), and produced alchemy, which became the basis of the emergence and development of modern chemistry. The long-term practice of alchemists has made people know a lot about natural minerals and accumulated experience in chemical experiments. But it is limited to the practical purpose of metallurgy and medicine, not to explore substances and their chemical changes.
2. The establishment of modern chemistry
The century from 16 to 17 is an important turning point in the development of chemistry. 166 1 Boyle's skeptical chemists believe that the purpose of chemical research is to understand the essence of matter, collect observed facts, discover the laws of things' changes through special experiments, and develop into an independent discipline to explore the mysteries of chemical changes in the material world. Realized the transformation from alchemy to modern chemistry.
1777 lavoisier put forward the theory of combustion oxidation, and 1789 systematically discussed the new theory of combustion oxidation centered on oxygen in the Outline of Chemistry. This is the first scientific chemical reaction theory in chemistry, which lists the first chemical element list of 33 elements known at that time. He also put forward the law of conservation of mass. 1808 dalton linked the macroscopic law of experience with the microscopic concept that matter is made up of atoms, and introduced the concept of atomic weight for the first time, which made chemistry really embark on the stage of quantitative development. At the same time, Baijiliu engaged in a lot of atomic weight determination and the formulation of element symbols. 18 1 1 year, Avon Gadereau published a paper entitled "A Method for Determining the Relative Mass of Atoms in Objects and the Proportion of Atoms Entering Compounds", and put forward the molecular hypothesis for the first time. 1896, Mendeleev published the paper "The Relationship between Element Attributes and Atomic Weight" and the first periodic table of elements. By the second half of the19th century, four branches of chemistry-inorganic chemistry, organic chemistry, analytical chemistry and physical chemistry had been formed one after another, and modern chemistry had been systematized, but it still belonged to the category of empirical science as a whole.
3. Development of modern chemistry
19 At the end of the 20th century, the three major discoveries of X-ray, radioactivity and electron in physics broke through the traditional concept that "atoms are inseparable and elements will not change". Planck's quantum theory and quantum mechanics, Einstein's photon theory and relativity, as well as the application of a series of physical experimental techniques, human beings know nature from the macro world to the micro world, and the whole chemical science not only has a solid theoretical foundation, but also has reliable experimental means. As a result, modern chemistry has made remarkable achievements in both basic theory and practical application, and its development speed and the breadth of research fields have greatly exceeded any previous period. Chemical science not only transits from qualitative description science to quantitative precision science, but also presents a high degree of differentiation and synthesis in its discipline development. What's more commendable is that chemistry has broken through the penetration and intersection of traditional subject concepts and adjacent subjects, showing its strong vitality.
It can be said that the chemistry of19th century is the atomic century. In the 20th century, with the help of new ideas, new concepts and new achievements in physics, the research focus of chemistry shifted to the molecular level, and chemistry became a molecular science.
Third, the prospect of chemistry in 2 1 century
The 20th century is an era of rapid scientific progress. As one of the basic disciplines of natural science, chemistry has also experienced a dazzling 100 years. Material production based on chemical processes has developed by leaps and bounds, which has profoundly affected all aspects of our global village. Today's high material civilization is inseparable from chemistry. However, when chemists proudly review the glory of this century, fewer and fewer people in society are afraid of chemical substances and choose chemistry as their profession. Some scientists in other fields think that chemical science has developed well, while others think that chemistry is being dismembered and dying out as an independent science.
After 1980s, when reviewing the development of chemistry, some chemists began to feel that chemists were too confined to their own fields. In order to develop chemical science, chemists must go out of pure chemistry and enter a big science with comprehensive development on the basis of various disciplines. At the same time, big science is calling for chemistry, which poses many challenges from life science, material science, environment, energy and even information science. It needs the new development of chemistry and the more active participation of chemists to solve many new problems such as complex systems, extreme conditions, mesoscopic and non-equilibrium States. Several important aspects of chemical development in the early 20th century may be: chemical reaction kinetics, molecular recognition, weak intermolecular interaction and molecular aggregation chemistry, synthesis and assembly chemistry, etc. The following briefly introduces several aspects of the frontier of modern chemistry:
1, Nanochemistry and Monomolecular Chemistry
From the point of view of chemistry and physics, the properties of nanoparticles are unusual because the proportion of atoms or molecules on their surfaces is unusually large. The research on its special optical, electrical, catalytic properties and special quantum effects has always been concerned by people. Qian Xuesen, a famous scientist in China, predicted as early as 199 1: I think nano and sub-nano structures will be the focus of development in the next century, which is a technological revolution, and thus another industrial revolution in 2 1 century.
On the other hand, with the help of STM /AFM and photography technology, we can observe many new phenomena and special effects at the single molecule level, and the revelation of these new phenomena and effects may lead to breakthroughs in some scientific problems.
2. The origin and evolution of elements and the universe.
Element is the foundation of all things and has always been the main object of chemical research. Nowadays, people's understanding of elements and their compounds has become increasingly systematic and theoretical, but the origin and evolution of elements themselves is still a subject worth exploring. Cosmic chemistry is the study of the chemistry of planets outside the earth. Due to the development of space technology, people have analyzed and studied the moon, Mars and other alien substances, which not only helps to study the origin of elements and the universe, but also helps to develop planets outside the earth.
3. The origin and evolution of life
Life science has entered the molecular level and needs the participation of chemical and synthetic research. Both the understanding and regulation of signal transduction and the gene regulation of modern hotspots will face the synthesis of various biological macromolecules and small molecules. For example, "Femtosecond Chemistry", which won the 1999 Nobel Prize in chemistry, can not only make people know the mechanism of chemical reaction concretely, but also observe the details of life movement and reveal the essence of life. Engels predicted that "the origin of life must be realized by chemical means". The great progress in chemistry proves the existence of this way. It can be summarized as a "chemical evolution" process from atom-inorganic molecule-organic molecule-biomacromolecule-primitive life. "For chemists, the biggest challenge in the next century is to create life" and "it is possible to develop a system of self-replication, self-organization and even biology". The president of the American Science Association believes that the view that chemistry is on the verge of creating life is not isolated. It has become a logical and inevitable conclusion that chemical evolution everywhere must be transformed into biological evolution as long as conditions are suitable. At present, scientists are conducting chemical research on the process of life in order to reveal and master the laws of molecular reactions in life and gradually realize the great goal of synthesizing life.
4. Chemistry of synthetic preparations
From the perspective of scientific development, synthetic chemistry is the core of chemistry and the most powerful means for future chemists to transform the world and create social wealth. Creating new synthetic reactions has always been a hot spot in the field of chemistry. It can be said that the development of all science and technology in the world is inseparable from synthetic preparative chemistry, which provides and guarantees them with a material basis. In the past 200 years, chemists have not only discovered and synthesized many natural compounds, but also artificially produced a large number of unnatural compounds. The number of all compounds in human society has reached 22.3 million (to 1999 65438+ February). And its increasing speed has increased from more than 600,000 species per year before the 1990s to 1 10,000 species today. With the arrival of 2 1 century and the rapid development of high technology, synthetic chemists are increasingly required to provide more compounds with new structures and functions, and on this basis, design and assemble molecular aggregates with various functions, such as molecular switches and molecular chips. At the same time, chemists are urgently required to synthesize all kinds of chemicals in today's application more specifically, efficiently, economically and environmentally.
The progress of materials science must first be the synthesis and preparation of new materials. For example, the preparation of yttrium barium copper oxide ceramics has caused a revolution and leap in high temperature superconductivity; Magic conductive polymer (characterized by light weight, good flexibility, low price and strong conductivity) will make foldable TV sets, computers worn on the body, luminous wallpaper, thin-film solar cells and so on appear. And will change our world. Therefore, the 2000 Nobel Prize in Chemistry was awarded to American scientist Haig, McDiarmid and Japanese scientist Hideki Shirakawa. With the acquisition of C60, people began to understand a new type of carbon molecular structure, and provided a new class of attractive material compounds, including nanotubes. Moreover, interstellar dust research proves that C60 may be the oldest molecule in the universe. So, how do they make up everything in the world? It can be said that all kinds of associations triggered by C60 are inspiring people to launch an impact on a higher scientific peak! Therefore, 1996 Nobel Prize in chemistry was awarded to British scientist Kruto and American scientists smalley and Cole.
Fourth, four understandings of chemistry learning in senior high school
1, grasp the concept and dig deep into the connotation and extension
Chemistry is a science that involves the change of matter and energy, and it is also a science that directly understands and transforms matter. It studies the laws of chemical changes of various substances, many of which are reflected in the relationship between concepts. Therefore, mastering concepts is the key to learning chemistry well. For a concept, it includes object, premise or hypothesis, expression and its relationship with other concepts. For example, the concept of molar volume of gas is aimed at gas, provided that the expression is 22.4 liters/mole under standard conditions. Under standard conditions, the molar volume of gas multiplied by density is equal to the molar mass of gas, which is one of its relations with other concepts. When using the concept, we must ensure that the object, premise and expression are correct, pay attention to its conditions and scope of application, and analyze the specific situation. In addition, we should understand the extension and development of the concept.
2. Grasp the essence and grasp the law of quantitative change.
Any law contains the relationship of quantity. Without quantity, there is no law. If you don't understand the relationship between quantity, you can't really grasp the law. Chemical calculation is often a headache or even a fear for students. In fact, the difficulty of chemical calculation lies not in calculation, but in the analysis and understanding of chemical concepts and the nature of chemical changes. In any chemical reaction, reactants and products are carried out according to a certain quantitative relationship. The essence of chemical reaction is that the particles (atoms and ions) that make up the reactants recombine to generate new substances. In this process, the kind and quantity of atoms will not change (law of conservation of mass). So, as long as the chemical reaction is analyzed clearly, how many effective particles are found during the reaction? Where did they come from? Where have you been? A series of physical quantities and related concepts centered on the quantity of matter are used to solve chemical calculation problems quickly and accurately.
3. Learn to associate and cultivate thinking ability
Chemistry is based on physics, biology and other related disciplines, and it didn't start until the third grade. In the study and research of chemistry, it is often necessary to understand the substance and its changing law by analyzing various phenomena, judging its composition and reasoning its structure. Every part of chemical knowledge is closely related. New knowledge is developed on the basis of old knowledge, and new knowledge can only be deeply understood by relying on old knowledge. Moreover, chemistry is everywhere in life. Therefore, in learning, we should learn to identify the "growing point" of knowledge, learn to use similar association, related association, analogy association, opposition association and subordinate association to spread the wings of association to the fullest, so as to learn from each other's strong points and systematize, structure and network the knowledge we have learned. At the same time, in the process of learning chemical knowledge and solving specific problems, cultivate and improve thinking ability.
4, hands-on experiments, improve hands-on ability.
Chemistry is a science based on experiments. Looking at many famous chemists in the history of chemistry, the reason why they can make great contributions to mankind is not only their spirit of being brave and good at practice, but also their spirit of being brave in innovation and diligent. The chemical knowledge and experimental skills of middle school students are the precious crystallization of previous practical experience. It is different from scientific experiments conducted by scientists. However, from the aspects of designing experiments, personally practicing, observing phenomena, accumulating facts and experiences, analyzing and synthesizing existing facts, abstracting and generalizing to draw scientific conclusions, cultivating the ability of analyzing and solving problems, and cultivating and improving scientific attitude and scientific literacy, it has many similarities with scientific experiments conducted by scientists. Therefore, in chemistry learning, we should attach great importance to chemical experiments. According to the characteristics of various experiments, on the premise of clear objectives, practice step by step, master the relevant reaction principle, device characteristics and operating procedures, master the skills of using commonly used instruments and reagents, observing and recording experimental phenomena, analyzing and processing experimental data, and simply drawing the schematic diagram of experimental devices. We should firmly establish the viewpoint based on experiments and link the knowledge of elemental compounds with the learning of basic theoretical knowledge through experiments, so that chemical experiments are not only an intuitive means to provide perceptual knowledge, but also an effective way and method to stimulate interest in learning chemistry, cultivate scientific attitude and innovative spirit, train scientific methods and improve practical ability.