Acids:
* Definition: Substances that donate hydrogen ions (H+) when dissolved in water.
* Characteristics:
* Taste sour
* React with metals to produce hydrogen gas
* Turn blue litmus paper red
* Have a pH less than 7
* Examples:
* Hydrochloric acid (HCl)
* Sulfuric acid (H₂SO₄)
* Citric acid (found in citrus fruits)
* Acetic acid (found in vinegar)
Bases:
* Definition: Substances that accept hydrogen ions (H+) or donate hydroxide ions (OH-) when dissolved in water.
* Characteristics:
* Taste bitter
* Feel slippery
* Turn red litmus paper blue
* Have a pH greater than 7
* Examples:
* Sodium hydroxide (NaOH)
* Potassium hydroxide (KOH)
* Ammonia (NH₃)
* Magnesium hydroxide (Mg(OH)₂)
Neutral Substances:
* Definition: Substances that are neither acidic nor basic. They have a balanced concentration of hydrogen and hydroxide ions.
* Characteristics:
* Do not taste sour or bitter
* Do not react strongly with acids or bases
* Have a pH of 7
* Examples:
* Pure water (H₂O)
* Table salt (NaCl)
* Sugar (C₁₂H₂₂O₁₁)
The pH Scale:
The pH scale is a numerical way to measure the acidity or basicity of a solution.
* 0 to 6.9: Acidic
* 7: Neutral
* 7.1 to 14: Basic
How Acids and Bases React:
Acids and bases neutralize each other in a chemical reaction called neutralization. This reaction produces salt and water.
Example:
* HCl (acid) + NaOH (base) → NaCl (salt) + H₂O (water)
Key Points:
* pH is a logarithmic scale: Each whole number change in pH represents a tenfold change in acidity or basicity.
* Acids and bases are essential for many biological and industrial processes.
* The concept of acidity and basicity is important for understanding chemical reactions and environmental issues.
