An acid is a substance that releases hydrogen ions (H⁺) when dissolved in water.
🔹 Acids usually have a sour taste, can corrode metals, and can change the color of indicators like litmus paper.
🧪 Properties of Acids
| Property | Description |
|---|---|
| Taste | Sour (e.g., lemon juice, vinegar) |
| pH value | Less than 7 (the lower the pH, the stronger the acid) |
| Turns blue litmus | Red |
| Conducts electricity | Yes (when dissolved in water) |
| Reacts with metals | Produces hydrogen gas |
| Neutralized by | Bases (alkalis) |
🔬 Common Examples of Acids
| Acid Name | Formula | Found In / Use |
|---|---|---|
| Hydrochloric acid | HCl | Stomach acid (digestion), cleaning metals |
| Sulfuric acid | H₂SO₄ | Batteries, fertilizers |
| Nitric acid | HNO₃ | Explosives, fertilizers |
| Acetic acid | CH₃COOH | Vinegar |
| Citric acid | C₆H₈O₇ | Citrus fruits (lemons, oranges) |
| Carbonic acid | H₂CO₃ | Carbonated drinks (fizzy sodas) |
🧪 Strong vs Weak Acids
| Type | Definition | Examples |
|---|---|---|
| Strong acid | Fully ionizes in water | HCl, H₂SO₄, HNO₃ |
| Weak acid | Partially ionizes in water | CH₃COOH, citric acid |
⚖️ Acid + Base = Salt + Water (Neutralization Reaction)
A key reaction:
Acid + Base → Salt + Water
📌 Example:
HCl + NaOH → NaCl (table salt) + H₂O
⚠️ Safety Tips When Handling Acids
-
Always wear gloves and goggles
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Never taste or touch lab acids
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Always add acid to water, not water to acid
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Store acids in safe, labeled containers
📘 Fun Facts
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Your stomach acid (HCl) has a pH of about 1–2
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Acid rain contains sulfuric and nitric acids
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Bees and ants inject formic acid when they sting
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Lemons, vinegar, and yogurt are safe, weak acids