1. **State the problem:** Diane drank 7 pints of water on a long hike. We need to convert this amount into quarts. 2. **Formula and conversion rule:** We use the conversion factor between pints and quarts. $$1 \text{ quart} = 2 \text{ pints}$$ This means to convert pints to quarts, divide the number of pints by 2. 3. **Calculate the conversion:** $$7 \text{ pints} = \frac{7}{2} \text{ quarts}$$ 4. **Simplify the fraction:** $$\frac{7}{2} = 3 \frac{1}{2}$$ 5. **Final answer:** Diane drank \textbf{3 1/2 quarts} of water. This is a mixed number in simplest form, and the unit is quarts.