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Summary of junior high school chemistry knowledge (memorization part)
1. Scientific names, common names and chemical formulas of substances
⑴Diamond, graphite: C⑵Mercury, mercury: Hg (3) Quick lime, calcium oxide: CaO (4) Dry ice (solid carbon dioxide): CO2 (5) Hydrochloric acid, hydrochloric acid: HCl (6) Sulfurous acid: H2SO3 (7) Hydrogen sulfuric acid: H2S (8) Hydrated lime, slaked lime: Ca(OH)2 (9) Caustic soda, caustic soda, caustic soda: NaOH (10) Soda ash: Na2CO3 Sodium carbonate crystal, soda ash crystal: Na2CO3·10H2O (11) Sodium bicarbonate, acid sodium carbonate: NaHCO3 (also called small Soda) (12) Bile vitriol, blue vitriol, copper sulfate crystal: CuSO4·5H2O (13) Verdigris, malachite: Cu2(OH)2CO3 (substances that decompose into three oxides) (14) Methanol: CH3OH Toxic, blind , Death (15) Alcohol, ethanol: C2H5OH (16) Acetic acid, acetic acid (16.6°C glacial acetic acid) CH3COOH (CH3COO- acetate ion) has acidic properties (17) Ammonia: NH3 (alkaline gas) (18) Ammonia, ammonia monohydrate: NH3·H2O (a common base, has the properties of an alkali, and is an alkali that does not contain metal ions) (19) Sodium nitrite: NaNO2 (industrial salt, toxic)
2. Color states of common substances
1. White solids: MgO, P2O5, CaO, NaOH, Ca(OH)2, KClO3, KCl, Na2CO3, NaCl, anhydrous CuSO4; Iron , Magnesium is silver-white (mercury is silver-white liquid)
2. Black solids: graphite, carbon powder, iron powder, CuO, MnO2, Fe3O4▲KMnO4 is purple-black
3 , Red solid: Cu, Fe2O3, HgO, red phosphorus ▲Sulfur: light yellow ▲ Cu2(OH)2CO3 is green
4. Solution color: Any solution containing Cu2 is blue; any solution containing Fe2 The solution is light green; the solution containing Fe3 is brown, and the other solutions are generally not colorless. (Potassium permanganate solution is purple-red)
5. Precipitation (i.e., salts and alkali insoluble in water): ① Salt: white ↓: CaCO3, BaCO3 (soluble in acid) AgCl, BaSO4 (also Insoluble in dilute HNO3), etc. ②Alkali: blue ↓: Cu(OH)2 reddish brown ↓: Fe(OH)3 white ↓: other alkali.
6. (1) Gases with irritating gases: NH3, SO2, HCl (all colorless)
(2) Colorless and odorless gases: O2, H2, N2, CO2, CH4, CO (highly toxic)
▲Note: Liquids with pungent odor: hydrochloric acid, nitric acid, acetic acid. Alcohol is a liquid with special gas.
7. Toxic, gas: CO Liquid: CH3OH Solid: NaNO2 CuSO4 (can be used as a bactericide, mixed with hydrated lime to form a sky blue viscous substance - Bordeaux liquid)
3. Solubility of substances
1. Solubility of salts
Substances containing potassium, sodium, nitrate, and ammonium are all soluble in water
Among the compounds containing Cl, only AgCl is insoluble in water, and the others are soluble in water;
Among the compounds containing SO42-, only BaSO4 is insoluble in water, and the others are soluble in water.
Only K2CO3, Na2CO3, and (NH4) 2CO3 are soluble in water, and the others are insoluble in water.
2. Solubility of alkali
Alkali that are soluble in water include: barium hydroxide, potassium hydroxide, calcium hydroxide, sodium hydroxide and ammonia. Other alkali are insoluble in water. Among the poorly soluble alkali, Fe(OH)3 is a reddish brown precipitate, Cu(OH)2 is a blue precipitate, and other poorly soluble alkali are white.
(Including Fe(OH)2) Note: AgCl and BaSO4 in the precipitate are insoluble in dilute nitric acid.
Other precipitates are soluble in acid. Such as: Mg(OH)2 CaCO3 BaCO3 Ag2 CO3, etc.
3. Most acids and acidic oxides can be dissolved in water. (Acidic oxide + water → acid) Most alkaline oxides are insoluble in water. Water can dissolve: barium oxide, potassium oxide, calcium oxide, sodium oxide (alkaline oxide + water → alkali)
IV. The best of chemistry
1. Earth’s crust The most abundant metallic element is aluminum. 2. The most abundant non-metallic element in the earth's crust is oxygen.
3. The most abundant substance in the air is nitrogen. 4. The hardest naturally occurring substance is diamond.
5. The simplest organic compound is methane. 6. The most mobile metal in the metal activity sequence is potassium.
7. The oxide with the smallest relative molecular mass is water. The simplest organic compound CH4
8. The gas with the smallest density under the same conditions is hydrogen. 9. The most conductive metal is silver.
10. The atom with the smallest relative atomic mass is hydrogen. 11. The metal with the smallest melting point is mercury.
12. The most abundant element in the human body is oxygen. 13. The element that makes up the most types of compounds is carbon.
14. The most widely used metal in daily life is iron. 15. China was the first to use natural gas; China’s largest coal base is in Shanxi Province; China was the first to use hydrometallurgy to smelt copper (discovered in the Western Han Dynasty [Liu An’s "Huainan Wanbi Shu" "Zeng Qing gets iron and turns it into copper"] , applied in the Song Dynasty); the first person to discover electrons was Thomson of England; the first person to conclude that air is composed of N2 and O2 was Lavoisier of France.
5. The "three" in junior high school chemistry
1. The three types of particles that constitute matter are molecules, atoms, and ions.
2. There are three commonly used reducing agents for reducing copper oxide: hydrogen, carbon monoxide, and carbon.
3. Hydrogen has three major advantages as a fuel: it is rich in resources, has high calorific value, and the product after combustion is water and does not pollute the environment. 4. There are generally three types of particles that make up atoms: protons, neutrons, and electrons. 5. There are only three types of ferrous metals: iron, manganese and chromium. 6. The elements that constitute matter can be divided into three categories: (1) metallic elements, (2) non-metallic elements, and (3) rare gas elements. 7. There are three types of iron oxides, and their chemical formulas are (1) FeO, (2) Fe2O3, and (3) Fe3O4.
8. There are three characteristics of a solution (1) homogeneity; (2) stability; (3) mixture.
9. Chemical equations have three meanings: (1) It indicates what substances participate in the reaction and what substances are produced as a result; (2) It indicates the ratio of the number of particles of molecules or atoms among the reactants and products; (3) Indicates the mass ratio between reactants and products. Chemical equations have two principles: based on objective facts; and following the law of conservation of mass. 10. Pig iron is generally divided into three types: white iron, gray iron, and ductile iron.
11. Carbon steel can be divided into three types: high carbon steel, medium carbon steel, and low carbon steel.
12. There are three types of iron ores commonly used in ironmaking: (1) Hematite (main component is Fe2O3); (2) Magnetite (Fe3O4); (3) Siderite ( FeCO3). 13. There are three main equipments for steelmaking: converter, electric furnace and open hearth.
14. The three reaction conditions often related to temperature are ignition, heating, and high temperature.
15. There are two ways to change a saturated solution into an unsaturated solution: (1) raising the temperature, (2) adding a solvent; there are three ways to change an unsaturated solution into a saturated solution: cooling down, adding a solute, and evaporating the solvent at a constant temperature. (Note: Substances whose solubility decreases with temperature, such as: calcium hydroxide solution changes from saturated solution to unsaturated solution: cooling, adding solvent; there are three ways to change unsaturated solution to saturated solution: heating, adding solute, constant temperature evaporation of solvent).
16. There are generally three methods for collecting gas: drainage method, upward emptying method, and downward emptying method.
17. The three main causes of water pollution: (1) waste residue, waste gas, and waste water in industrial production; (2) arbitrary discharge of domestic sewage; (3) pesticides and chemical fertilizers used in agricultural production It flows into the river with the rain.
18. There are three commonly used fire extinguishers: foam fire extinguishers; dry powder fire extinguishers; liquid carbon dioxide fire extinguishers.
19. The change of solubility of solid substances with temperature can be divided into three categories: (1) The solubility of most solid substances increases with temperature; (2) The solubility of a few substances is affected by temperature. The effect is very small; (3) The solubility of very few substances decreases with the increase of temperature. 20. There are three reasons why CO2 can extinguish fires: it cannot burn, it cannot support combustion, and it is denser than air. 21. Elemental substances can be divided into three categories: metallic elements; non-metallic elements; and rare gas elements. 22. The three most important fossil fuels in the world today are: coal, oil, and natural gas.
23. The three black oxides that should be remembered are: copper oxide, manganese dioxide, and ferric oxide.
24. Hydrogen and carbon elements have three similar chemical properties: stability at room temperature, flammability, and reducibility.
25. Three times light blue appears in the textbook: (1) Liquid oxygen is light blue (2) Sulfur burns in the air with a weak light blue flame, (3) Hydrogen burns in the air Burns with light blue flame.
26. Three blue colors related to copper element: (1) copper sulfate crystal; (2) copper hydroxide precipitation; (3) copper sulfate solution. 27. There are "three supports" in the filtration operation: (1) The lower end of the funnel is close to the inner wall of the beaker; (2) The end of the glass rod is lightly pressed against the third layer of the filter paper; (3) The edge of the beaker holding the filtrate is close to the glass Support and attract traffic.
28. Three major gas pollutants: SO2, CO, NO2
29. The flame of the alcohol lamp is divided into three parts: outer flame, inner flame, and flame core. The outer flame The highest temperature.
30. There are "three no's" principles when taking medicines: (1) Do not touch the medicines with your hands; (2) Do not put your nose to the mouth of the container to smell the gas; (3) Do not taste the medicines . 31. The three major chemical processes in ancient times: paper making, gunpowder making, and porcelain burning. 32. Three industrial wastes: waste water, waste residue, and waste gas. 34. Three instruments that can be directly heated: test tubes, crucibles, and evaporating dishes (in addition There are also burning keys)
35. The three invariants of atoms explained by the conservation of mass: the type does not change, the number does not increase or decrease, and the quality does not change
36. It may explode when mixed with air and ignited Three gases: H2, CO, CH4 (actually any flammable gas and dust). 37. Three products of coal carbonization (chemical change): coke, coal tar, and coke oven gas
38. Three characteristics of concentrated sulfuric acid: water absorption, dehydration, and strong oxidation
39. Three prohibitions on using alcohol lamps: burning, adding alcohol to the burning lamp, and blowing it out with your mouth
40. Three steps for preparing a solution: calculation, weighing (measurement), and dissolution
41. The top three most abundant elements in biological cells: O, C, H
42. Three equations in atoms: Nuclear charge = Number of protons = Number of electrons outside the nucleus = Atomic number
43. Three types of particles that constitute matter: molecules, atoms, and ions
6. "Definitely" and "not necessarily" in chemistry
1 , There must be physical changes in chemical changes, and there may not necessarily be chemical changes in physical changes.
2. Metals are not necessarily solid at room temperature (for example, Hg is liquid), and non-metals are not necessarily all gases or solids (for example, Br2 is liquid). Note: Metals and non-metals refer to simple substances. , cannot be confused with the constituent elements of matter
3. The atomic group must be a charged ion, but the atomic group is not necessarily an acid radical (such as NH4, OH-);
The acid radical is not necessarily an acid radical either. Atomic groups (such as Cl - called hydrochlorate)
4. Slow oxidation does not necessarily cause spontaneous combustion. Combustion must be a chemical change. An explosion is not necessarily a chemical change. (For example, a pressure cooker explosion is a physical change.
) 5. There may not always be neutrons in the nucleus (for example, H atoms do not have neutrons). 6. Atoms are not necessarily smaller than molecules (you cannot say "molecules are bigger and atoms are smaller")
The fundamental difference between molecules and atoms is that molecules can be divided and atoms cannot be divided in chemical reactions
7 , Substances composed of the same element are not necessarily simple substances, but may also be a mixture of several simple substances.
8. Particles with 8 electrons in the outermost shell are not necessarily atoms of rare gas elements, but may also be cations or anions. 9. The number of electrons in the outermost shell of an atom with a stable structure is not necessarily 8. (The first layer is the outermost 2 electrons) 10. Particles with the same nuclear charge are not necessarily the same element.
(Because particles include atoms, molecules, and ions, while elements do not include molecules or atomic groups composed of multiple atoms) Only mononuclear particles (one atom and one nucleus) with the same nuclear charge must belong to the same species element.
11. (1) A concentrated solution is not necessarily a saturated solution; a dilute solution is not necessarily an unsaturated solution. (For different solutes) (2) A saturated solution of the same substance is not necessarily more concentrated than an unsaturated solution. (Because the temperature is not determined, just like the temperature is certain) (3) The solution after the crystals are separated must be a saturated solution of a certain substance. Crystals may not precipitate after the saturated solution is cooled. (4) At a certain temperature, the solubility value of any substance must be greater than the solute mass fraction value of its saturated solution, that is, S must be greater than C.
13. A reaction in which elements and compounds participate or are generated is not necessarily a displacement reaction. But there must be a change in the valence of the elements. 14. There may not necessarily be changes in the valence of elements in decomposition reactions and combination reactions; there must be changes in the valence of elements in substitution reactions; there must be no changes in the valence of elements in metathesis reactions. (Note: Oxidation-reduction reactions must involve changes in the valence of elements) 15. Elemental substances must not undergo decomposition reactions.
16. The same element does not necessarily show the same valence in the same compound. Such as NH4NO3 (the N in the front is -3 valent, and the N in the back is 5 valent)
17. The composition of salt does not necessarily contain metal elements. For example, NH4 is a cation and has the properties of a metal ion, but it is not metal ions. 18. Cations are not necessarily metal ions. Such as H, NH4.
19. In the composition of compounds (oxides, acids, bases, salts), those that definitely contain oxygen elements are oxides and bases; those that do not necessarily (may) contain oxygen elements are acids and salts; Acids and alkalis must contain hydrogen elements; salts and oxides may not contain hydrogen elements; salts and alkalis do not necessarily contain metal elements (such as NH4NO3, NH3·H2O); acids may contain metal elements (such as : HMnO4 is called permanganic acid), but all material compositions must contain non-metallic elements. 20. Salt solutions are not necessarily neutral. For example, Na2CO3 solution is alkaline.
21. The solution of acid salt is not necessarily acidic (that is, the pH is not necessarily less than 7), such as NaHCO3 solution is alkaline. However, sodium bisulfate solution is acidic (NaHSO4 =Na H SO42-), so the substance that can ionize hydrogen ions is not necessarily an acid.
22. An acid solution must be an acidic solution, but an acidic solution is not necessarily an acid solution. For example, H2SO4 and NaHSO4 solutions are both acidic, and NaHSO4 is a salt. (Acid solution is an aqueous solution of acid, and acidic solution refers to a solution containing H)
23. An alkaline solution must be an alkaline solution, but an alkaline solution is not necessarily an alkaline solution. For example: NaOH, Na2CO3, and NaHCO3 solutions are all alkaline, while Na2CO3 and NaHCO3 are salts. Alkaline solution is an aqueous solution of alkali, and alkaline solution refers to a solution containing OH-)
24. Alkaline oxides must be metal oxides, and metal oxides are not necessarily alkaline oxides.
(For example, Mn2O7 is a metal oxide, but it is an acid oxide, and its corresponding acid is permanganic acid, that is, HMnO4); remember: among alkaline oxides, only K2O, Na2O, BaO, CaO can dissolve in water and react with water to form an alkali.
25. Acidic oxides are not necessarily non-metal oxides (such as Mn2O7), and non-metal oxides are not necessarily acidic oxides (such as H2O, CO, NO). ★Common acidic oxides: CO2, SO2, SO3, P2O5, SiO2, etc. Most acidic oxides can be dissolved in water and react with water to generate the corresponding acid. Remember that silicon dioxide (SiO2) is insoluble in water.
26. The reaction that produces salt and water is not necessarily a neutralization reaction.
27. All chemical reactions are not necessarily basic reaction types. Examples that are not basic reactions include: ①The reaction between CO and metal oxides; ②The reaction between acidic oxides and alkali; ③The combustion of organic matter.
28. In any displacement reaction involving elemental iron (reaction of iron with acids and salts), the iron must be divalent after the reaction (that is, ferrous salts are generated). 29. For any displacement reaction between metal and acid, the mass of the solution will definitely increase after the reaction.
Whenever a metal reacts with a salt solution, to judge the mass change of the solution before and after the reaction, just look at the relative atomic mass of the metal participating in the reaction and the relative atomic mass of the metal produced. "Replace a large amount with a small one to gain weight, exchange a small amount with a large one to lose weight."
30. Whenever metals of the same mass and same valence state react with acids, the greater the relative atomic mass, the less mass of hydrogen gas will be produced. 31. All metals that can react with water at room temperature (such as K, Ca, Na) must not undergo displacement reactions with salt solutions; but their reactions with acids are the most intense.
If Na is added to the CuSO4 solution, the reaction that occurs is: 2Na 2H2O =2NaOH H2 ↑; 2NaOH CuSO4 =Cu(OH)2 ↓ Na2SO4.
31. In all air exhausting methods (no matter upward or downward), the air guide pipe must be extended to the bottom of the gas collecting bottle.
32. The air tightness of the gas generating device must be checked before filling it with medicines.
Be sure to check the purity before igniting or heating flammable gases.
33. When writing a chemical formula, positive elements are not always written on the left. For example, if NH3, CH4
34, 5g of a certain substance are put into 95g of water, and after it is fully dissolved, the solute mass fraction of the resulting solution may not necessarily be equal to 5.
It may be equal to 5, such as NaCl, KNO3, etc.; it may also be greater than 5, such as K2O, Na2O, BaO, SO3, etc.; it may also be less than 5, such as crystal hydrates, Ca(OH)2, CaO, etc. .
◆Under the same conditions, the solution obtained after CaO or Ca(OH)2 is dissolved in water has the smallest solute mass fraction