You're fu*king kidding me, right?
Your pilot license should be revoked just for posting this. What sort of chemicals do you put in YOUR fuel tank?
All jet engines make a lot of water as a byproduct of combustion. It's real cold up in the flight levels. Contrails are ice crystals illuminated by sunlight. Depending on altitude, humidity, winds aloft, they could last a long time or not be visible at all. High altitude clouds are also frozen water droplets. Contrails are basically long, narrow clouds.
Some old, old jets might actually produce some real smoke.