PH scale

Definition

The pH scale is a logarithmic scale used to measure the acidity or alkalinity of a solution, ranging from 0 to 14. A pH value of 7 is neutral, values below 7 are acidic, and values above 7 are basic (alkaline).

5 Must Know Facts For Your Next Test

1. The pH scale is logarithmic, meaning each whole number change represents a tenfold change in hydrogen ion concentration.
2. Water has a neutral pH of 7 because it dissociates into equal concentrations of hydrogen ions (H+) and hydroxide ions (OH-).
3. Acidic solutions have higher concentrations of hydrogen ions and lower pH values.
4. Basic solutions have higher concentrations of hydroxide ions and higher pH values.
5. The pH level can affect biochemical reactions and processes in living organisms.

Review Questions

• What does a pH value below 7 indicate about a solution?
• How does the pH scale relate to hydrogen ion concentration?
• Why is water considered neutral on the pH scale?

Related terms

Buffer: A substance that minimizes changes in the pH of a solution by absorbing or releasing hydrogen ions.

Acid:

A substance that increases the hydrogen ion concentration in a solution, resulting in a lower pH.

Base:

A substance that decreases the hydrogen ion concentration in a solution, resulting in a higher pH.