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pH Scale
Chemistry helps us understand the acidic or basic nature of substances around us. One of the most important concepts in Class 10 Science Chapter – Acids, Bases and Salts is the pH scale. The pH scale is used to measure how acidic or basic a substance is.
Different substances such as lemon juice, soap solution, vinegar, and water have different pH values. The pH scale helps scientists, doctors, farmers, and industries determine the chemical nature of solutions accurately.
Understanding the pH scale is important for board examinations as well as daily life applications. In this article, you will learn about pH full form, pH scale acids and bases, water pH scale, pH scale examples 0-14, and the importance of pH in simple and easy-to-understand language.
1.0What is pH?
The pH value of a substance tells us whether the substance is acidic, basic, or neutral. The term pH is used to measure the concentration of hydrogen ions in a solution.
The pH full form is "Potential of Hydrogen."
Sometimes it is also called:
- Power of Hydrogen
- Potential Hydrogen
The pH scale was introduced by Danish scientist Søren Peder Lauritz Sørensen in 1909. pH Scale is a numerical scale used to measure the acidic or basic strength of substances.
The pH scale generally ranges from: 0 to 14
The value depends on the concentration of hydrogen ions present in the solution.
pH Scale Name and Range
The pH scale name comes from the term “Potential of Hydrogen.”
Lower pH values indicate stronger acids, while higher pH values indicate stronger bases.
2.0pH Scale: Acids and Bases
The pH scale acts as a chemical yardstick. It is divided into three distinct zones based on the concentration of hydrogen ions (H+) versus hydroxyl ions (OH-):
- pH < 7 (Acids): Solutions with a pH lower than 7 are acidic. The lower the number, the stronger the acid. (Higher concentration of H+ ions).
- pH = 7 (Neutral): A pH of exactly 7 is completely neutral. It is neither acidic nor basic.
- pH > 7 (Bases/Alkalis): Solutions with a pH higher than 7 are basic (or alkaline). The higher the number, the stronger the base. (Higher concentration of OH- ions).
Important Concept: As pH decreases from 7 to 0, acidity increases. As pH increases from 7 to 14, basicity increases.
3.0pH Scale Examples 0-14
Understanding pH scale examples helps students remember the concept easily.
pH Scale Examples from 0 to 14
These examples help understand the acidic and basic strength of substances.
4.0Water pH Scale
The pH of water depends heavily on its purity and what is dissolved in it:
- Pure Distilled Water: Has a pH of exactly 7.0. It is perfectly neutral because the concentration of H+ and OH- ions is perfectly balanced.
- Normal Drinking Water / Tap Water: Typically ranges between 6.5 and 8.5 depending on local mineral content.
- Ocean Water: Is slightly basic, hovering around a pH of 8.1 due to dissolved salts and carbonates.
5.0Universal Indicator and pH Scale Colors
Universal Indicator changes color according to pH values.
These colors help identify the strength of acids and bases.
6.0pH in Everyday Life (Class 10 CBSE Corner)
In Class 10 Science, you need to know how pH affects living organisms:
- Our Body: Functions best within a narrow pH range of 7.0 to 7.8.
- Tooth Decay: Starts when the pH in our mouth falls below 5.5. Bacteria break down food particles to produce acids that corrode tooth enamel. Toothpaste is basic to neutralize this.
- Soil pH: Plants require a specific pH range for healthy growth. If soil is too acidic, farmers treat it with quicklime {CaO} or slaked lime {Ca(OH)}2.
- Self-Defense by Animals: Honeybee stings inject an acidic liquid, causing pain. Applying a mild base like baking soda provides relief.