This invention offers effective and efficient method to produce and to use LIQUID defined as activated liquid which contains sufficient amount of micro bubbles of diameter less than 10 micrometers. LIQUID exhibits very useful properties for the purification of liquid, sterilization, extinguishment of undesirable bubbles, preservation of freshness of food, storage of gas in liquid, the decomposition of pollutants etc. The method to produce LIQUID comprises a means to rotate a rotor installed in a fixed tube wherein the rotor and the fixed tube are provided with a set of permanent magnets and a set of linear protuberances, and liquid and gas are introduced in the gap formed between the fixed tube and the rotor by pumping means driven by the motor. The micro bubbles are effectively produced with the repulsive magnetic field generated by the S (or N) pole of at least 30% of the whole magnets faced with the said gap. An annular activator made from far infrared emitting materials is assembled in the path of liquid in order to increase the efficiency for producing LIQUID.