I'm not sure what you mean by "precitation." Can you please provide more context or clarify your question?
Precipitation forms when water droplets in clouds grow large enough to fall due to gravity. Not all clouds have enough moisture or updrafts to support precipitation. Additionally, some clouds may be too high in the atmosphere for precipitation to reach the ground before evaporating.
1. Presence of Preciptate 2. Color Change 3. Smell Change 4. Temperature change Basically, look for: Visual Indicators (precipitate, colour changes, fizzing/bubbling) Smell, Touch (temperature increase/decrease)