Lesson-specific diagram for Local water/soil chemistry investigation and solution mastery. It visualizes the reasoning sequence tied to $\text{question}\to\text{safe method}\to\text{data}\to\text{chemical model}\to\text{evaluation}$. Text alternative: Integrate solubility, molarity, ion chemistry, analysis technique, uncertainty, and local/place context in a complete investigation. Choose a representation that matches the chemical scale and evidence; do not infer more precision or mechanism than the data support.