What is pH?

by Yogi P - April 21, 2025

Do you know what is pH?

The pH is a fundamental concept and used in chemistry, biology and environmental science. It play very important role in various processes, like from digestion process in our human body to the health of aquatic ecosystems.

But exactly what is the pH and why it is that important? In this article we will provides a detailed explanation of pH, its measurement, applications, and significance  of pH in our everyday life.

What is pH?

The pH is a measure of the acidity or alkalinity of a given solution. The term “pH” full form is “potential of hydrogen” and it refers to the concentration of the hydrogen ions (H⁺) in a given solution. The scale of the pH ranges from 0 to 14, the breakdown of this range is as below:

• pH 7: Neutral (e.g., pure water)
• pH below 7: Acidic (higher concentration of H⁺ ions)
• pH above 7: Alkaline or basic (lower concentration of H⁺ ions)

The pH scale is logarithmic, which means that each unit of pH represents a tenfold difference in acidity or alkalinity. For an example, a given solution with a pH of 5 is ten times more acidic than a solution which is having a pH of 6.

How is pH Measured?

The pH can be measured using several methods as follows:

Method 1. pH Meters:

A pH meter is an electronic device that measures the concentration of hydrogen ion in any given solution. It provides accurate and precise readings of pH and that is the reason it is commonly used in laboratories and industries.

Method 2. pH Indicator Strips:

pH strips are paper strips coated with pH-sensitive dyes. When dipped into a solution, they change color based on the pH level. The color is then compared to a reference chart to determine the pH.

Method 3. Liquid pH Indicators:

Liquid indicators, such as phenolphthalein or litmus solution, change color in response to pH changes. These are often used in titrations and simple experiments.

The pH Scale: Examples of Common Substances

Here are some examples of common substances and their approximate pH values:

• pH 0: Battery acid (highly acidic)
• pH 2: Lemon juice, vinegar
• pH 4: Tomato juice, acid rain
• pH 6: Milk, urine
• pH 7: Pure water (neutral)
• pH 8: Seawater, baking soda
• pH 10: Milk of magnesia
• pH 12: Soapy water
• pH 14: Sodium hydroxide (highly alkaline)

Why the pH is so important?

pH is a critical parameter in various fields like for example:

Biological Systems:

• Human Body: The human body maintains a tightly regulated pH balance. For example, blood has a pH of approximately 7.4, and deviations can lead to serious health issues.
• Digestion: Stomach acid has a pH of around 1.5 – 3.5, which is essential for breaking down food and killing harmful bacteria.

Agriculture:

• Soil pH affects nutrient availability and plant growth. Most crops thrive in slightly acidic to neutral soils (pH 6–7).

Environmental Science:

• The pH of water bodies (e.g., lakes, rivers) impacts aquatic life. Fish and other organisms are sensitive to pH changes, and acid rain can lower the pH of water, harming ecosystems.

Industry:

• pH control is crucial in industries like food processing, pharmaceuticals, and wastewater treatment. For example, the fermentation process in beer and wine production relies on specific pH levels.

Household Applications:

• pH is important in cleaning products, swimming pool maintenance, and even skincare. For instance, alkaline cleaners are effective for grease removal, while acidic cleaners work well for mineral deposits.

Factors affecting the pH

Several factors can influence the pH of a solution, including:

• Temperature: pH values can change with temperature, as the dissociation of water and other compounds varies.
• Dissolved Substances: Acids, bases, and salts can alter the pH of a solution.
• Biological Activity: Microorganisms and plants can release acids or bases, affecting pH levels in soil or water.

How to adjust the pH

pH can be adjusted using acids or bases:

• To Lower pH (Increase Acidity): Add an acid, such as hydrochloric acid (HCl) or citric acid.
• To Raise pH (Increase Alkalinity): Add a base, such as sodium hydroxide (NaOH) or baking soda (sodium bicarbonate).

Common misconceptions about the pH

pH is Only About Acids and Bases:

• While pH measures acidity and alkalinity, it also reflects the balance of ions in a solution, which is important for chemical reactions and biological processes.

All Acids and Bases are Dangerous:

• Not all acids and bases are harmful. For example, citric acid (found in fruits) and baking soda (a mild base) are safe for consumption.

pH is the Same in All Solutions:

• pH varies depending on the composition of the solution. For instance, the pH of rainwater differs from that of seawater due to dissolved gases and minerals.

Conclusion

pH is a vital concept that influences countless aspects of science, industry, and daily life. Understanding what pH is, how it is measured, and its applications can help you make informed decisions in fields ranging from healthcare to environmental conservation. Whether you’re testing the pH of your garden soil, maintaining a swimming pool, or studying chemical reactions, pH is a key parameter to consider.