adding velocity to water

I am going to try and be as descriptive as I can because I know that helps. I am a beginner to Unity and the game I am making involves firefighting. I want to make a fire extinguisher that fires water particles when the player presses a key. The issue I am having is in adding velocity to particles that are from a particle system and making those particles only emit when mouse is down as I have only been able to make those particles invisible when the mouse is not clicked the issue with this is I would like to make it so that when my "water" comesinto contact with the fire in the game,the fire is extinguished.Bt if the partiles are just invisable this would cause a lot of unwanted issues. also is it even possible to make it so that when those water particles come into contact with the fire the fire is extinguished. Ay help on this would be greatly appreciated as I am really struggling and have been looking everywhere as to how to do this.