any of the major appearances or aspects in which a thing of varying modes or conditions manifests itself to the eye or mind. 2. a stage in a process of change or development: Each phase of life brings its own joys. 3. a side, aspect, or point of view: This is only one phase of the question.
The pH of a neutral solution is 7. At this pH, the solution has equal concentrations of both the H+ and OH- ions, which is 10^-7 mole/litre. The presence of both the hydrogen and hydroxyl ions in equimolar concentrations makes the solution neutral.
An acidic solution has many hydrogen ions (H+) and a pH below 7. An alkaline, or basic, solution has very few hydrogen ions and a pH above 7. A neutral solution has a pH of 7. Recall that the substrate is the molecule that the enzyme acts on, and the products are the molecules produced by the reaction.