What Are Acids and Bases?

Acids and bases are fascinating chemical substances that we encounter in everyday life. The tangy taste of a lemon or orange? That’s because of an acid! The slippery feel of soap? That’s due to a base. Let’s dive deeper into understanding these substances.

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1. Acids

Definition

Acids are chemical substances that produce hydrogen ions (H⁺) when dissolved in water. These hydrogen ions are responsible for the characteristic properties of acids.

Properties of Acids

1. Taste: Acids have a sour taste. For instance, vinegar (acetic acid) and citrus fruits (citric acid) are sour.
2. Reaction with Metals: Acids react with certain metals, like zinc or magnesium, to produce hydrogen gas.
   • Example:
     Zn+2HCl→ZnCl2+H2↑
3. Effect on Litmus: Acids turn blue litmus paper red.
4. Conductivity: Since acids release ions in water, they are good conductors of electricity.

Examples of Acids

• Natural Acids: Citric acid in lemons, lactic acid in curd, and acetic acid in vinegar.
• Mineral Acids: Hydrochloric acid (HCl), sulfuric acid (H₂SO₄), and nitric acid (HNO₃).

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2. Bases

Definition

Bases are substances that produce hydroxide ions (OH⁻) when dissolved in water.

Properties of Bases

1. Taste: Bases have a bitter taste. For example, baking soda and soap.
2. Feel: Bases feel slippery or soapy to the touch.
3. Reaction with Acids: Bases neutralize acids to form salt and water.
   • Example:
     NaOH + HCl → NaCl + H₂O
4. Effect on Litmus: Bases turn red litmus paper blue.
5. Conductivity: Like acids, bases also conduct electricity in aqueous solutions.

Examples of Bases

• Strong Bases: Sodium hydroxide (NaOH), potassium hydroxide (KOH).
• Weak Bases: Ammonium hydroxide (NH₄OH).

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3. Salts

Definition

Salts are ionic compounds formed when acids react with bases. They are composed of a positive ion (cation) from the base and a negative ion (anion) from the acid.

Properties of Salts

1. Taste: Most salts are salty (like table salt), but some have other tastes.
2. Solubility: Many salts dissolve in water, but some are insoluble.
3. Electrical Conductivity: Salts conduct electricity in their molten or aqueous states.

Examples of Salts

• Sodium chloride (NaCl) – table salt.
• Potassium nitrate (KNO₃) – used in fertilizers.

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Indicators: Identifying Acids and Bases

Indicators are substances that help us identify whether a solution is acidic or basic by changing color.

Common Indicators

1. Litmus:
   • Acids turn blue litmus red.
   • Bases turn red litmus blue.
2. Phenolphthalein:
   • Colorless in acids, pink in bases.
3. Methyl Orange:
   • Red in acids, yellow in bases.

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Did You Know?

• Ant stings contain formic acid, which causes irritation. Applying baking soda (a base) neutralizes the effect.
• Lemon juice can remove rust stains because of its acidic properties.

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Quick Recap

Property	Acids	Bases
Taste	Sour	Bitter
Litmus Test	Blue to Red	Red to Blue
Examples	HCl, Citric Acid	NaOH, NH₄OH
Reaction	React with metals to form hydrogen gas	Feel slippery and react with acids

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Practice Questions

1. Define acids and bases with examples.
2. Write the chemical reaction between hydrochloric acid and sodium hydroxide.
3. What are indicators? Name two and explain their color change in acids and bases.
4. Explain why acids conduct electricity.

Acids, bases, and salts are integral to both chemistry and daily life. This lesson is just the beginning of understanding their fascinating properties and reactions. Stay curious, and let’s explore further in upcoming lessons!