Introduction
Why does lemon juice taste sour, but soap feels slippery? Why do antacids help when you have acidity? These are all results of chemical substances around us known as acids, bases, and salts.
They’re not just in your chemistry lab—they’re in your food, cleaning products, medicines, and even your body. With the help of the pH scale, we can tell how strong or weak these substances are.
In this lesson, we’ll understand what acids, bases, and salts really are, how they work, and where they appear in daily life.
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What Are Acids?
Acids are substances that release hydrogen ions (H⁺) when dissolved in water.
Key Properties:
- Taste sour
- Turn blue litmus red
- Conduct electricity in water
- Corrosive (can damage skin and metals)
Examples of Acids:
| Acid | Found In |
| Citric Acid | Lemon, oranges |
| Acetic Acid | Vinegar |
| Lactic Acid | Curd, sour milk |
| Hydrochloric Acid (HCl) | Stomach acid, labs |
| Sulfuric Acid (H₂SO₄) | Used in car batteries |
What Are Bases?
Bases are substances that release hydroxide ions (OH⁻) when dissolved in water.
Key Properties:
- Taste bitter
- Feel slippery or soapy
- Turn red litmus blue
- Can also be corrosive
When bases that dissolve in water are called alkalis.
Examples of Bases:
| Base | Use |
| Sodium hydroxide (NaOH) | Used in soap and drain cleaners |
| Magnesium hydroxide | Used in antacids |
| Calcium hydroxide | Used for whitewashing walls |
| Ammonium hydroxide | Used in window cleaners |
What Are Salts?
Salts are formed when an acid reacts with a base—this is called a neutralization reaction.
General Reaction:
Acid + Base → Salt + Water
This is how common table salt (NaCl) is made!
Examples:
| Reaction | Salt Formed |
| HCl + NaOH → NaCl + H₂O | Sodium chloride |
| H₂SO₄ + Ca(OH)₂ → CaSO₄ + H₂O | Calcium sulfate |
| HNO₃ + KOH → KNO₃ + H₂O | Potassium nitrate |
Indicators: Tools That Detect Acids and Bases
Indicators are substances that change color when added to acidic or basic solutions. They help us detect if a solution is acidic, basic, or neutral.
Common Indicators:
| Indicator | In Acid | In Base |
| Litmus | Red | Blue |
| Phenolphthalein | Colorless | Pink |
| Methyl Orange | Red | Yellow |
| Universal Indicator | pH color scale | pH color scale |
The pH Scale – Measuring Strength of Acids and Bases
The pH scale is a scale from 0 to 14 that shows how acidic or basic a solution is.
- 0 to 6 → Acidic
- 7 → Neutral
- 8 to 14 → Basic (Alkaline)
Lower pH = Stronger acid
Higher pH = Stronger base
Real-World pH Examples:
| Substance | pH Range |
| Battery Acid | 1 |
| Lemon Juice | 2 |
| Pure Water | 7 (neutral) |
| Toothpaste | 8–9 |
| Soapy Water | 12 |
Importance of pH in Daily Life
| Situation | Why pH Matters |
| Stomach Acidity | Too much HCl causes discomfort → use antacids (basic) |
| Tooth Decay | Bacteria produce acids → use basic toothpaste to neutralize |
| Agriculture | Soil pH affects plant growth → lime used to adjust pH |
| Shampoo & Skincare Products | Made to match skin’s pH (around 5.5) to avoid irritation |
Core Concepts Table
| Term | Meaning |
| Acid | Substance that gives H⁺ ions in water |
| Base | Substance that gives OH⁻ ions in water |
| Salt | Product of acid + base reaction |
| Neutralization | Reaction of acid and base to form salt and water |
| pH Scale | Measures acidity/basicity (0 to 14) |
| Indicator | Substance that shows acid or base using color |
Frequently Asked Questions
Q1. What is the pH of pure water?
Exactly 7 (neutral)
Q2. What color does litmus turn in acid?
Blue litmus turns red.
Q3. What is a neutralization reaction?
When an acid reacts with a base to form salt and water.
Q4. What’s the use of antacids?
Antacids are basic substances used to neutralize excess stomach acid.
Q5. Why do strong acids and bases need to be handled carefully?
Because they are corrosive—they can burn skin or damage materials.
Fun Facts
- “pH” stands for “potential of hydrogen”.
- Bee stings are acidic – baking soda (a base) helps relieve pain.
Wasp stings are basic – vinegar (an acid) helps neutralize. - Litmus comes from lichens – a natural indicator!
- Hydrangea flowers change color based on soil pH—blue in acidic soil, pink in basic soil.
Conclusion
Understanding acids, bases, and salts isn’t just useful for exams—it’s key to knowing how the world around you works. From the soap in your bathroom to the juice in your glass, and even the medicine in your stomach—these chemical reactions are happening all the time.
With the pH scale as your guide and indicators as your tools, you can explore the world of Chemistry with confidence and curiosity.
