Investigating Acids, Bases, and the pH ScaleThe pH scale is a numerical scale from 0 to 14 that measures how acidic or basic a substance is. A pH of 7 is neutral (pure water), below 7 is acidic, and above 7 is basic (alkaline). Strong acids, like hydrochloric acid, have a very low pH (close to 0), while strong bases, like sodium hydroxide, have a very high pH (close to 14).
Indicators help determine whether a substance is an acid or a base. Litmus paper turns red in acids and blue in bases, while the universal indicator changes color to show the exact pH level.
When acids and bases react, they undergo neutralization, producing salt and water. For example, hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH) to form sodium chloride (table salt) and water. This reaction is important in real life, such as in antacids, which neutralize excess stomach acid, and in agriculture, where lime is used to reduce soil acidity.
Indicators help determine whether a substance is an acid or a base. Litmus paper turns red in acids and blue in bases, while the universal indicator changes color to show the exact pH level.
When acids and bases react, they undergo neutralization, producing salt and water. For example, hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH) to form sodium chloride (table salt) and water. This reaction is important in real life, such as in antacids, which neutralize excess stomach acid, and in agriculture, where lime is used to reduce soil acidity.
- Acids and Bases:
- Acids have a pH less than 7, bases have a pH greater than 7, and a pH of 7 is neutral.
- Common acids: Hydrochloric acid (HCl), Sulfuric acid (H₂SO₄), Citric acid (found in fruits).
- Common bases: Sodium hydroxide (NaOH), Ammonia (NH₃), Calcium hydroxide (Ca(OH)₂).
- Indicators:
- Litmus paper:
- Turns red in acids, blue in bases.
- Universal indicator:
- Shows a range of colors to indicate exact pH.
- Phenolphthalein:
- Colorless in acids, pink in bases.
- Methyl orange:
- Red in acids, yellow in bases.
- Litmus paper:
- Reactions Between Acids and Bases:
- Neutralization: Acid + Base → Salt + Water.
- Example: Hydrochloric acid (HCl) + Sodium hydroxide (NaOH) → Sodium chloride (NaCl) + Water (H₂O).
- Real-Life Applications:
- Stomach Acid Neutralization: Antacids (bases) help relieve heartburn by neutralizing stomach acid.
- Soil Treatment: Farmers add lime (a base) to acidic soil to improve plant growth.
- Acid Rain Effects: Can damage buildings, aquatic life, and forests.
