Why does the gas pressure in a closed vessel increase when heated?

The fact that the gas pressure in a closed vessel increases with heating is associated with the properties of gaseous substances.
The main ones are:
1) the molecules of the gaseous substance move chaotically;
2) their speed can vary depending on the temperature of the substance.
The speed of movement of molecules increases, with increasing temperature and vice versa, with decreasing temperature, the speed of molecules decreases.
Therefore, if the velocity of the molecules is greater, and the volume of the vessel does not change, the pressure on the vessel walls will increase.