Paddle sequence

Stroke order of water: vertical hook, horizontal left/horizontal hook, left and right.

Introduction of water:

Water (chemical formula h? O), an inorganic substance composed of hydrogen and oxygen, is nontoxic and drinkable. At normal temperature and pressure, it is a colorless and odorless transparent liquid, which is called the source of human life and an important substance to maintain life, also called hydrogen oxide.

Water is one of the most common substances on the earth, and about 7 1% of the earth's surface is covered with water. It is an important resource of all life, including inorganic compounds and human beings, and it is also the most important component of organisms. Although its content in the air is small, it is an important part of the air.

Pure water has very weak conductivity and belongs to extremely weak electrolyte. Water in daily life has obvious conductivity because it dissolves other electrolytes and has more anions and cations.

Physical properties:

Although water is the standard of many physical constants, it has some special physical properties. Unlike most substances that decrease in volume and increase in density when solidified, water increases in volume and decreases in density when frozen;

Different from the situation that the density of most substances increases with the decrease of temperature, the density of water has a maximum value at 277. 14K; Among all solid and liquid substances, water has the largest specific heat capacity; Although the molecular weight of water is not large, its boiling point and heat of vaporization are quite high.

Generally speaking, the boiling point and freezing point of homologues increase with the increase of molecular weight, while the boiling point and freezing point of water and its homologues with larger molecular weight are higher. Among many substances, water has a particularly large dielectric constant, so it is also an excellent polar solvent. All these "anomalies" are closely related to the formation of hydrogen bonds and the association of water.

Chemical properties:

Water must be a very stable compound because it has a great heat of formation. In fact, at the high temperature of 3000K, the decomposition rate of water is only 1 1. 1%, and the reaction is reversible.

Obviously, water absorbs a lot of heat when it dissociates. At 1000K and 202.65kPa, 2 moles of gaseous water need to absorb 495.8kJ of heat to decompose into H2 and O2. It needs 572.04kJ at 3000K k.