What s so special about junior high school chemistry, junior high school chemistry is commonly known

Chemistry isn't too hard, and there's no need to be nervous.

Critical: 1. Memorize the name of the substance and the chemical formula.

2. Master the properties of matter.

3. Be able to write the chemical equation of the reaction.

4 There are several more principles.

Junior high school chemistry is too simple, in fact, junior high school chemistry textbooks are popular science books, with very little professional knowledge, junior high school chemistry is to let students establish an impression of chemistry, there is not much use, and a lot of knowledge in it is very one-sided, chemical reactions are actually quite complex, but junior high school textbooks are obviously simplified.

Sodium chloride (NaCl): table salt; Sodium carbonate (Na2CO3): soda ash, soda, mouth alkali; Sodium hydroxide (NaOH):

caustic soda, caustic soda, caustic soda; Calcium oxide (CAO): quicklime; Calcium hydroxide (Ca(OH)2): hydrated lime, slaked lime; Carbon dioxide solids (CO2):

Dry ice; Hydrochloric acid (HCl): hydrochloric acid; Basic copper carbonate (Cu2(OH)2CO3): patina.

1. Potassium permanganate: commonly known as gray manganese oxygen, chemical formula KMNO4, commonly used as a disinfectant in medicine.

2. Sodium chloride: commonly known as table salt, chemical formula NaCl, can be used as an important condiment, preservative, snow melting agent, etc.

3. Sodium carbonate: commonly known as soda ash, soda, chemical formula Na2CO3, widely used in detergent, glass, papermaking, textile and other industries.

4. Sodium bicarbonate: commonly known as baking soda, chemical formula NaHCO3, is a baking powder for baking pasta and pastries, and a drug for hyperacidity.

5. Sodium hydroxide: commonly known as caustic soda, caustic soda and caustic soda, chemical formula NaOH, widely used in soap, petroleum, papermaking, textile, printing and dyeing and other industries, kitchen cleaners contain sodium hydroxide.

6. Calcium carbonate: the main component of marble and limestone, the chemical formula CaCO3, is widely used in construction and raw materials for cement.

7. Calcium hydroxide: commonly known as hydrated lime, slaked lime, chemical formula Ca(OH)2, its aqueous solution is commonly known as lime water, often used to improve acidic soil, used as building materials, preparation of Bordeaux liquid, stone sulfur mixture, etc.

8. Calcium oxide: commonly known as quicklime, chemical formula CAO, as a food desiccant.

9. Hydrogen peroxide: commonly known as hydrogen peroxide, chemical formula H2O2, used as a disinfectant in medicine.

10. Copper sulfate pentahydrate: commonly known as bile alum, blue alum, chemical formula CuSO4?5H2O is used as a fungicide in agriculture, a pesticide Bordeaux liquid is prepared with lime, and a swimming pool is used for disinfection in sports.

11. Methane: the main component of natural gas and biogas, with the chemical formula CH4, is an important gaseous fuel.

12. Ethanol: common name alcohol, chemical formula C2H5OH, the main component of alcoholic beverages, 10% ethanol is added to automotive ethanol gasoline, which belongs to renewable green energy.

13. Acetic acid: commonly known as acetic acid, chemical formula CH3COOH, the usual vinegar contains about 3%-5% acetic acid.

14. Solid carbon dioxide: commonly known as dry ice, chemical formula CO2, used for artificial rainfall, film and television special shooting, etc.

1. The most abundant metal element in the earth's crust 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 substance that occurs naturally is diamond.

5. The simplest organic matter is methane.

6. The most active metal in the metal activity sequence table is potassium.

7. The oxide with the smallest relative molecular mass is water. The simplest organic compound is CH4.

8. The gas with the least density under the same conditions is hydrogen.

9. The metal with the strongest electrical conductivity 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 with the largest variety of constituent 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; The first to use wet copper smelting was in China; The first to discover the electron was Thomson in England; The first to conclude that air is composed of N2 and O2 was Lavoisier in France.

16. There are three kinds of iron ore commonly used in ironmaking:

1) Hematite (the main component is Fe23).

2) Magnetite (Fe3O4).

3) Siderite (FeCO3).

17. The main equipment of steelmaking includes three land chains: converter, electric furnace and open-hearth.

18. The three reaction conditions that are often related to temperature are ignition, heating, and high temperature.

19. There are two ways to turn a saturated solution into an unsaturated solution

1) Heat up. 2) add solvent; There are three ways to change unsaturated solution to saturated solution: cooling, adding solubility and evaporating solvent at constant temperature.

Note: Substances whose solubility decreases with temperature, such as: calcium hydroxide solution changes from saturated solution to unsaturated solution

Cooling, solvent addition; There are three ways to change unsaturated solution to saturated solution: heating up, adding solutes, and evaporating solvents at constant temperature).

20. There are generally three methods for collecting gas: drainage method, upward emptying method, and downward emptying method.

21. 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 fertilizers used in agricultural production flow into rivers with rainwater.

22. There are three types of fire extinguishers commonly used: foam fire extinguishers; dry chemical fire extinguishers; Liquid carbon dioxide fire extinguisher.

23. The solubility of solid substances varies with temperature, which can be divided into three categories:

1) The solubility of most solid substances increases with the increase of temperature.

2) The solubility of a few substances is very little affected by temperature.

3) The solubility of a very small number of substances decreases with the increase of temperature.

The properties of a substance that can only be manifested in a chemical change are called chemical properties.

Chemical properties of junior high school: such as: flammability, stability, acidity, alkaline, oxidation, reduction, etc., corrosiveness, etc.

Chemistry is a kind of natural science, which studies the properties, composition, structure and change laws of matter at the molecular and atomic levels.

Chemistry is a natural science that studies the properties, composition, structure, changes, uses, preparation methods, and changes of substances. Chemistry is closely related to industry, agriculture, daily life, medicine, materials, etc.

For example, coal, oil and natural gas are burned to produce carbon dioxide and other substances.

The object of chemical research deals with the interrelationships between matter, or between matter and energy. Traditional chemistry is often about the contact and change of two substances, i.e., a chemical reaction, or the process by which one substance becomes another. These changes sometimes require the use of electromagnetic waves, which are responsible for initiating chemical reactions.

Sometimes, though, chemistry doesn't have to be about reactions between substances. Spectroscopy is the study of the relationships between matter and light, and these relationships do not involve chemical reactions.

Originally, the total mass of copper and copper oxide was 10 grams, and the copper produced after being reduced by carbon monoxide was grams. Illustrates that the mass of the solid is reduced in grams. The mass of the reduced solids is the mass of oxygen in copper oxide.

That is, the mass of the oxygen element in copper oxide is grams. This makes it possible to calculate the mass of copper oxide. It is equal to the mass of the gram oxygen element.

Divide by the mass fraction of oxygen in copper oxide. The mass of copper oxide is calculated to be equal to eight grams. So the mass fraction of copper oxide is eight grams of copper oxide divided by the total mass of the solid by ten grams multiplied by one hundred percent equals 80%.

Hello, the third junior high school students will answer for you:

The physical properties of common substances, especially the color, are as follows the Rubber Pin Zheng I Finishing Liang Song.

1. Precipitate color.

1.White precipitate: AGCI, BASO4, CaCO3, MG(OH)2, AL(OH)3

2.Reddish-brown precipitate: Fe(OH)3

3.Blue bucket color precipitation: Cu(OH)2

Diamond, graphite: c

Mercury, mercury: hg

3) Quicklime, calcium oxide: CAO

4) Dry ice (solid carbon dioxide): CO2

5) Hydrochloric acid, hydrochloric acid: HCl

6) Sulfurous acid: H2SO3

7) Hydrosulfuric acid: H2S

8) Hydrated lime, slaked lime: Ca(OH)2 limestone CaCO3

9) Caustic soda, caustic soda, caustic soda: NaOH

10) Soda ash: Na2CO3 sodium carbonate crystals, soda ash crystals: Na2CO3·10H2O

11) Sodium bicarbonate, acid sodium carbonate: NaHCO3 (also called baking soda).

12) Cholelum, blue alum, copper sulfate crystals: CuSO4·5H2O

13) Apatina, malachite: Cu2(OH)2CO3 (a substance that decomposes to form three oxides).

14) Methanol: CH3OH is toxic, blind, and dead.

15) Alcohol, ethanol: C2H5OH

16) Acetic acid, acetic acid (glacial acetic acid) CH3COOH (CH3COO-acetate ion) have the general properties of acids.

17) Ammonia: NH3 (alkaline gas).

18) Ammonia, ammonia monohydrate: NH3·H2O (a common alkali with the universality of alkali, and a kind of alkali that does not contain metal ions).

19) Sodium nitrite: nano2 (industrial salt, toxic).

20) Sulfuric acid: H2SO4

Diamond, graphite: C (test point: graphite conductive, diamond does not conduct).

Mercury: Hg (test center: the only metal that is liquid at room temperature).

Quicklime, calcium oxide: cao (can be used as a desiccant.)

Hydrated lime, slaked lime: Ca(OH)2 Dry ice (solid carbon dioxide): CO2 (can be used as a refrigerant.)

Three strong acids: hydrochloric acid, hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3).

Sulfurous acid: H2SO3

Hydrosulfuric acid: H2S

Sodium hydroxide (common name: caustic soda, caustic soda, caustic soda): NaOH

Sodium carbonate (common name: soda ash): Na2CO3 sodium carbonate crystals, soda ash crystals: Na2CO3·10H2O

Sodium bicarbonate, acid sodium carbonate (commonly known as baking soda): NaHCO3

Copper sulfate crystal (common name: bile alum, blue alum): CuSO4·5H2O

Basic copper carbonate (commonly known as patina, malachite): Cu2 (OH) 2CO3 (test point: a substance that can be decomposed into three oxides).

Ammonia: NH3 (test center: alkaline gas).

Sodium nitrite: nano2 (industrial salt, toxic).

Here are a few very important things:

Hydrogen peroxide (common name: hydrogen peroxide): H2O2 (test center: preparation of O2, Mno2 as catalyst).

Potassium chlorate: KCLO3 is used to produce oxygen, and Mno2 is used as a catalyst.

Potassium permanganate: KMno4 for oxygen.

Iron oxide: the main component of Fe2O3 rust.

Limestone CaCO3 is used to produce CO2

Sulphur · sulphur: s

Mercury. Mercury: hg

Sodium chloride. Table salt: Nacl

Sodium carbonate. Soda ash. Soda: Na2CO3

Sodium bicarbonate. Baking soda: nahco3

Sodium hydroxide. Caustic soda. Caustic soda. Charged sodium: Naoh

Potassium hydroxide. Charged potassium: koh

Potassium nitrate. Saltpeter. Fire Nitrate: KNO3

Potassium permanganate. Gray manganese oxygen. PP powder: KMNO4

Potassium carbonate. Potash. Oxaline: K2CO3

Calcium hydroxide. Hydrated lime. Slaked lime: Ca(OH)2

Calcium oxide. Quicklime: cao

Calcium carbonate. Limestone. Marble: caco3

Magnesium oxide. White as earth. Burning bitter soil: MGO

Magnesium carbonate. Magnesite: MGCo3

Alumina. Corundum. Bauxite: al2o3

Potassium aluminum sulfate crystals. Alum: kal(SO4).

Iron oxide. Hematite. Rust: Fe2O3

Ferric oxide. Magnetite. Iron black: Fe3O4

Ferrous sulfate crystals. Alum:

Copper sulphate crystals. Cholelum. Blue Alum:

Basic copper carbonate. Apatina: Cu2(OH)2CO3

Manganese dioxide. Pyrolite: mno2

Silicon dioxide. Sand. Quartz: SiO2

Carbon monoxide. Gas: co

Carbon dioxide. Dry ice: CO2 (solid).

Ammonium sulphate. Ammonium sulfate: (NH4)2SO4

Ammonium nitrate. Ammonium nitrate: NH4NO3

Ammonium bicarbonate. Ammonium carbide: H4HCO3

Calcium phosphate. Phosphate rock powder: Ca3(PO4)2

Methane. Biogas: CH4

Ethanol. Alcohol: C2H5OH

Acetic acid. Acetic acid. Glacial acetic acid: CH3COOH

1. Sometimes you will be given a letter or a letter plus a number, such as O2 or Fe, which are all elemental, but note that the gas molecule must be followed by a number, for example, it asks you if O is elemental, which is definitely not, because it represents an atom. But if it's solid Fe. It can mean either an atom or an element.

A chemical compound is a pure substance formed by the combination of two or more substances. To put it simply, it is not a letter such as CO2, it is a combination of C and O2, it is not a mixture.

Purified substances, including elemental substances and compounds. In other words, the general term for elemental substances and compounds is called pure substances.

Mixture, the general exam likes to say so-and-so solution, air, oil, coal or so-and-so mixture of gases, as long as there are these words, it is a mixture.