1. Pure substances and mixtures: A substance composed of a single type of matter is called a pure substance, while a substance composed of multiple types of matter is called a mixture. For example, nitrogen and oxygen are pure substances; Air is a mixture.

2. Elements and Compounds: A substance composed of a single element is called an element; a substance composed of two or more elements is called a compound.

3. Organic and Inorganic Substances: Substances other than hydrocarbons and their derivatives are generally referred to as inorganic; compounds composed of carbon and hydrogen, along with their derivatives, are called organic.

4. Small molecules and polymers: Substances with low molecular weights are called small molecules; substances with high molecular weights are referred to as polymers (also known as macromolecules), such as resins.

5. Physicochemical indicators: the fundamental physical and chemical properties of a substance, including odor, color, state, characteristics, specific gravity, melting point, boiling point, solubility, and so forth.

6. Purity: The purity of a raw material refers to its degree of cleanliness and, by extension, to the level of impurities it contains. The higher the purity, the fewer and less diverse the impurities present. Chemical raw materials can be classified according to their purity into… Industrial grade and reagent-grade, two major categories.

7. Purity grades of reagent-grade raw materials are generally classified into four levels.

Extra‑pure grade (GR: Guaranteed reagent), also known as first‑class or guaranteed reagent, with a purity of 99.8%, is the highest‑purity reagent available, containing the lowest levels of impurities. It is suitable for critical, precision analytical work and scientific research and is identified by a green label.

Analytical reagent (AR), also known as a second‑grade reagent, has a high purity of 99.7%, slightly lower than that of superior grade reagents. It is suitable for critical analytical applications and general research work and is identified by a red label.

Chemically pure (CP), also known as a third‑grade reagent, has a purity of ≥ 99.5%. Its purity is considerably lower than that of analytical grade and it is suitable for routine analytical work in industrial and mining settings as well as in schools. It is labeled in blue (dark blue).

Experimental reagent (LR: Laboratory reagent), also known as a fourth-grade reagent.

8. Melting point: the temperature at which a substance transitions from the solid state to the liquid state.

9. Boiling point: The temperature at which a substance transitions from the liquid phase to the gas phase.

10. Flash point: the temperature at which a substance, when heated, reaches its ignition point.

11. Flash point : The lowest temperature at which a substance’s gas can ignite.

12. Dropping point: One of the indicators characterizing the properties of grease. It is the temperature at which a grease sample, under standard conditions, melts and drips from the orifice.

13. Freezing point: the temperature at which a liquid turns into a solid.

14. Viscosity: Dynamic viscosity An abbreviation of.

It was previously considered to be dynamic viscosity, kinematic viscosity, and… Relative viscosity The collective term for the three is inaccurate. The symbol η(μ) is defined as η = τ/D, where τ is the shear stress and D is the velocity gradient in the direction perpendicular to the flow layer. In other words, it is the shear stress of a fluid divided by the velocity gradient along the flow layer. Its SI unit is the pascal-second; in chemical engineering, the millipascal-second is commonly used. In the older centimeter–gram–second system, the unit was the poise. poise 。

15. Hardness:

(1) A water quality parameter that reflects the salinity of water. It is the total concentration of soluble calcium, magnesium, iron, and other salts in water, expressed in milliequivalents per liter.

(2) A physical property of minerals. It refers to a mineral’s resistance to external mechanical forces, particularly to scratching.

(3) A mechanical property of materials. It refers to a material’s ability to resist being scratched or indented by another substance on its surface.

16. Roughness: The degree of surface irregularity of an object, expressed as Ra.

17. Density: Denoted by the symbol ρ, also known as mass density, it is defined as mass divided by volume, i.e., ρ = m/V. Common units include kg/m³ and g/mL.

18. Baumé Degree: The relative density of a solution measured with a Baumé hydrometer is expressed as the Baumé degree. There are two types of Baumé hydrometers: one, called the heavy scale, is used to measure solutions denser than water; the other, called the light scale, is used to measure solutions lighter than water (such as ammonia solution).

19. Fineness: Generally refers to the diameter of particles in a powdered substance, typically expressed in micrometers.

20. Concentration: Abbreviation for molar concentration.

When the term “concentration” is applied to a particular physical quantity, it denotes that quantity divided by its volume. Examples include mass concentration, volume concentration, amount-of-substance concentration, and number‑of‑molecules concentration. In the past, the expression “percent concentration” was often used rather imprecisely; this term did not specify which type of concentration was intended, merely indicating that the unit was percent (%). Percent concentrations are classified as weight percent and volume percent, while molar concentration corresponds to amount-of-substance concentration, with units expressed in moles per liter. Normality: Normality was formerly a unit used to express solution concentration, denoted by the symbol N and defined as 1 N = 1 gram‑equivalent per liter. For example, when 1 gram‑equivalent of sulfuric acid (49.04 g) is dissolved in water to make 1 liter of solution, the normality of that solution is 1 N. This unit is no longer in common use; it has been replaced by the concentration unit mole per liter. When equivalent particles are taken as the fundamental unit, a normality of y N corresponds to a concentration of y moles per liter.

21. Median lethal dose (LD50): Also known as the lethal dose that causes death in half of the test animals. It refers to the amount of a substance required to produce acute toxicity resulting in the death of 50% of the experimental animals—such as rats or mice—following a single oral, intravenous, or dermal administration. The unit is milligrams per kilogram of body weight.

22. Solution: Also known as a homogeneous mixture, it consists of two or more substances uniformly blended together. Based on the state of aggregation, solutions can be classified into gaseous solutions, liquid solutions, and solid solutions. Solvent: The medium in which the solute is dispersed within a solution is called the solvent. Solute: The substance that is dispersed in the solution is called the solute.

23. Chemical reaction: a type of change in which new substances are formed. During such a process, both the composition and the chemical properties of the substances undergo alteration.

24. Redox Reactions: A reaction in which a substance combines with oxygen is called oxidation. A reaction in which an oxygen-containing substance loses oxygen is called reduction (in the narrow sense). The loss of electrons is oxidation, while the gain of electrons is reduction (in the broad sense).

25. Neutralization reaction: the interaction between an acid and a base.

26. Carbonization: (1) refers to dry distillation; (2) is the abbreviated term for carbonic acid.

27. Explosive limits: the concentration (or pressure) range within which a flammable gas or vapor mixed with air can undergo an explosion.

28. State: gas, liquid, solid, semi-solid, powder

29. Coal gas: a type of natural gas. Main components: carbon monoxide and hydrogen.

30. Flammable and explosive materials:

Flammable substances: This category of chemicals refers to flammable liquids, liquid mixtures, or liquids containing solid substances that are highly susceptible to ignition and combustion at ambient temperatures. Examples include gasoline, ethanol, and benzene. Most of these substances are organic compounds and exhibit the following characteristics:

① Highly flammable; ② Explosive; ③ Highly mobile and readily dispersible; ④ Thermally expandable; ⑤ Incompatible with oxidizers and acids; ⑥ Toxic.

Explosive substances: These chemicals are capable of undergoing violent chemical reactions under external stimuli—such as heat, pressure, or impact—resulting in the instantaneous release of large volumes of gas and heat, which cause a rapid increase in surrounding pressure and lead to an explosion. An explosion is a process in which a substance abruptly transitions from one state to another, releasing enormous amounts of energy and performing mechanical work.

The main characteristics of a chemical explosion are: rapid reaction rate, substantial heat release, and the generation of large volumes of gas. Corrosive substances are solids or liquids that can cause burns to human tissues and damage materials such as metals. When in contact with skin, they produce visible necrosis within four hours.

31. Weathering and Deliquescence: The phenomenon whereby a hydrated crystal loses part or all of its water of crystallization at room temperature and in relatively dry air, leading to the destruction of the crystal structure. Deliquescence: The process by which certain substances soluble in water absorb moisture from the surrounding humid air and dissolve. This occurs because, upon absorbing water, these substances form solutions whose vapor pressure is lower than the partial pressure of water vapor in the air.

32. Drying and Moisturizing

Drying: In the chemical industry, it is a process in which heat is directly applied to vaporize moisture (or solvent) from the material, and the resulting vapor is carried away by an inert gas.

Moisturization: The process of supplying external moisture to an object that inherently requires it.

33. Water Absorption and Dehydration: The ability of a material to absorb water is referred to as water absorption; the process of removing water from a substance is called dehydration.