To determine which substance is neutral based on its pH value, we need to understand the pH scale. The pH scale ranges from 0 to 14:
- A pH of 7 is considered neutral.
- A pH less than 7 is considered acidic.
- A pH greater than 7 is considered basic (or alkaline).
Given the pH values for the substances:
- Lemon has a pH of 2.0, which is acidic.
- Water has a pH of 7.0, which is neutral.
- Tomato has a pH of 4.0, which is acidic.
- Soap has a pH of 10.0, which is basic.
Since a pH of 7.0 is neutral and the substance with this pH value is Water, we can conclude that Water is the neutral substance.
Therefore, the neutral substance is Water.