What are the key points of chemistry in the first semester of junior high school?

Chemistry knowledge points in the third year of junior high school are:

1. Knowledge point 1:

Reduction reaction: In a reaction, the oxygen of an oxygenated compound is taken away (not a basic type of reaction in chemistry). Oxidation reaction: The chemical reaction of a substance with oxygen (not a basic type of chemical reaction).

Slow oxidation: An oxidation reaction that proceeds very slowly, even imperceptibly.

Spontaneous combustion: Spontaneous combustion caused by slow oxidation.

Catalyst: A substance that can change the chemical reaction rate of other substances during chemical changes, but its mass and chemical properties do not change before and after chemical changes. (Note: 2H2O2 ==2H2O + O2 This reaction Mno2 is the catalyst).

2. Knowledge point 2:

Law of Conservation of Mass: The sum of the masses of the substances participating in the chemical reaction is equal to the sum of the masses of the substances formed after the reaction. (Before and after the reaction, the number, type, and mass of atoms remain the same; The kind of element also does not change)

Solution: One or several substances are dispersed into another substance to form a homogeneous, stable mixture.

Composition of the solution: solvent and solute.

3. Knowledge point three:

The solute can be solid, liquid, or gaseous; When solid and gas are soluble in liquid, solid and gas are solutes, and liquids are solvents; When two liquids dissolve each other, the one with the largest amount is the solvent and the less liquid is the solute. When there is water in the solution, regardless of the amount of water, we are used to treating water as a solvent and the others as solutes.

Solid solubility: At a certain temperature, the mass dissolved by a solid substance when it reaches saturation in 100 grams of solvent is called the solubility of the substance in this solvent.

Acids: Compounds in which the cations formed during ionization are all hydrogen ions.

For example: HCl==H+ +Cl HNO3==H+ +NO3H2SO4==2H+ +SO42.

4. Knowledge point 4:

Base: A compound in which all anions formed during ionization are hydroxide ions.

For example: koh==k+ +oh naoh==na+ +oh.

ba(oh)2==ba2+ +2oh。

Salt: Compounds that form metal ions and acid ions during ionization, such as: KNO3==K+ +NO3 NA2SO4==2NA+ +SO42 BACl2==BA2+ +2Cl.

Acidic oxides (not necessarily non-metallic oxides): Oxides that react with alkalis to form salts and water.

5. Knowledge point 5:

Basic oxides (metal oxides): Oxides that react with acids to form salts and water.

Crystal hydrate: substances containing crystal water (e.g., 2CO3·Na 10H2O, CuSO4·2O).

Deliquescence: The phenomenon that a substance can absorb moisture in the air and become damp.

Chemistry knowledge points in the third year of junior high school are:1. Chemical change: the change of other substances is generated.

2. Physical change: no change in other substances.

3. Physical properties: properties that do not need to undergo chemical changes to manifest themselves.

Such as: color, state, density, odor, melting point, boiling point, hardness, water solubility, etc.).

4. Chemical properties: the properties of substances in chemical changes.

Such as: flammability, combustibility, oxidation, reduction, acidity and alkalinity, stability, etc.).

5. Pure substance: composed of a substance.

6. Mixture: It is composed of two or more pure substances, and each substance retains its original properties.

7. Element: A general term for a class of atoms with the same number of nuclear charges (i.e., the number of protons).

8. Atom: It is the smallest particle in chemical change, and it cannot be divided in chemical change.

9. Molecule: It is the smallest particle that maintains the chemical properties of a substance, and can be redivided in chemical changes.

10. Elemental: a pure substance composed of the same element.

11. Compound: a pure substance composed of different elements.

12. Oxide: Among the compounds composed of two elements, one of which is oxygen.

13. Chemical formula: The formula that uses element symbols to represent the composition of matter.

14. Relative atomic mass: The value obtained by comparing the mass of other atoms with the mass of a carbon atom with 1 12 as the standard.

The relative atomic mass of an atom Relative atomic mass Number of protons Number of neutrons (because the mass of an atom is mainly concentrated in the nucleus).

15. Relative molecular mass: the sum of the relative atomic masses of each atom in the chemical formula.

1. Colorless liquid: water, hydrogen peroxide. 2. Blue solution: copper sulfate solution, copper chloride solution, copper nitrate solution.

3. Light green solution: ferrous sulfate solution, ferrous chloride solution, ferrous nitrate solution.

4. Yellow solution: ferric sulfate solution, ferric chloride solution, ferric nitrate solution.

5. Purple-red solution: potassium permanganate solution.

6. Purple solution: litmus solution.