To study the thermal properties of gases in a container, the research object is a system composed of a large number of molecules in the container

definition

example

In the absence of external influences, as long as a long enough time passes, the state parameters of each part of the system can reach a stable state. This state is called an equilibrium state.

The two systems should be in contact to transfer heat, and the state parameters of the two systems will affect each other and change respectively.

After a period of time, the respective state parameters no longer change, indicating that the two systems have reached equilibrium.

If two systems are each in thermal equilibrium with a third system, then the two systems must also be in thermal equilibrium with each other.

When two systems are in thermal equilibrium, they must have some common thermal properties

The physical quantity that characterizes this "common thermal property"

To describe temperature quantitatively, there must be a method

The temperature represented by the thermodynamic temperature scale

symbol

unit

The relationship between the pressure and volume of a certain mass of gas when the temperature remains constant

When the temperature of a certain mass of a certain gas remains constant, the pressure p is inversely proportional to the volume V

formula

The process by which the volume of a certain mass of a certain gas changes with temperature when the pressure remains constant.

When the pressure of a certain mass of a certain gas remains constant, its volume V is directly proportional to the thermodynamic temperature T.

formula

The process by which the pressure of a certain mass of a certain gas changes with temperature when the volume remains constant.

For a certain mass of a certain gas, when the volume remains constant, the pressure p is proportional to the thermodynamic temperature T

formula

The pressure is not too high

The temperature is not too low

Molecular size and interaction force can be ignored, and the kinetic energy loss of gas molecules colliding with the wall can also be ignored.

Follow the experimental laws of gases at any temperature and pressure

For an ideal gas of a certain mass, when the temperature remains constant, the average kinetic energy of the molecules is constant. In this case, when the volume decreases, the number density of molecules increases, and the number of molecules that collide with the wall of the device per unit time and unit area increases, and the pressure of the gas increases. .

When the temperature of a certain ideal gas of a certain mass increases, the average kinetic energy of the molecules increases; only when the volume of the gas increases simultaneously and the number density of the molecules decreases can the pressure remain unchanged.

For a certain mass of an ideal gas, when the volume remains constant, the number density of molecules remains constant. In this case, when the temperature increases, the average kinetic energy of the molecules increases, and the pressure of the gas increases.

reason

Phenomenon

reason

Phenomenon

The phenomenon of rising liquid in a thin tube of wetting liquid and the falling phenomenon of non-wetting liquid in a straw

application

Organic molecules are mostly rod-shaped, with the rod length being more than 5 times the diameter of the rod.

fluidity of liquid

fixed arrangement of crystal molecules

Liquid crystals with molecular alignment have optical anisotropy

Life science field, etc.

example

Natural and regular geometric shapes

Has a fixed melting point

Anisotropic

example

irregular appearance

no fixed melting point

Homosexuality

example

irregular appearance

Has a fixed melting point

isotropic

diamond crystal structure