Let's go through each substance one by one to identify its nature based on its pH value.
### Step-by-Step Solution:
1. Pure Water, pH = 7.0
- The pH scale ranges from 0 to 14, with pH 7 being neutral.
- Since pure water has a pH of exactly 7.0, it is classified as neutral.
2. Lake Water, pH = 6.5
- A pH value less than 7 indicates acidity.
- Since the pH of lake water is 6.5, which is less than 7, it is classified as acidic.
3. Baking Soda Solution, pH = 9.0
- A pH value greater than 7 indicates basicity.
- Since the pH of the baking soda solution is 9.0, which is greater than 7, it is classified as basic.
4. Soapy Water, pH = 12.0
- A pH value greater than 7 also indicates basicity.
- Since the pH of soapy water is 12.0, which is significantly greater than 7, it is classified as basic.
### Summary:
- Pure Water: pH = 7.0 → neutral
- Lake Water: pH = 6.5 → acidic
- Baking Soda Solution: pH = 9.0 → basic
- Soapy Water: pH = 12.0 → basic
Thus, we have classified each substance based on its pH value as follows:
- Pure water is neutral.
- Lake water is acidic.
- Baking soda solution is basic.
- Soapy water is basic.
