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Introduction to Acids, Bases and Salts

Have you ever tasted a lemon or an unripe mango? What about the bitter taste of neem leaves or the soapy taste of soap solution? The sour taste comes from substances called acids, while the bitter taste comes from substances called bases. When acids and bases react with each other, they form salts.

🌍 Real-Life Applications​

Acids, bases, and salts are all around us in our daily lives:

Acids in our daily life:

  • Lemon juice and vinegar in cooking
  • Curd and sour milk products
  • Vitamin C (ascorbic acid) in fruits
  • Citric acid in citrus fruits
  • Tamarind (used in many Indian dishes)

Bases in our daily life:

  • Soap for washing
  • Baking soda for cooking
  • Toothpaste for cleaning teeth
  • Antacids for treating stomach acidity
  • Many cleaning products

Salts in our daily life:

  • Common salt (sodium chloride) for flavor in food
  • Baking powder for making cakes rise
  • Washing soda for cleaning
  • Epsom salt for relieving muscle pain
  • Fertilizers for plants

🧪 How Do We Identify Acids and Bases?​

We can identify acids and bases without tasting them (which is dangerous!) by using special substances called indicators. Indicators change color when they come in contact with acids or bases.

Natural Indicators​

These are substances found in nature that change color in acids and bases:

  1. Litmus paper: A purple dye extracted from lichens

    • Turns red in acids
    • Turns blue in bases

  2. Turmeric: A common spice in Indian cooking

    • Yellow in acids
    • Turns reddish-brown in bases

  3. Red cabbage juice: Made from boiled red cabbage

    • Red in acids
    • Green in bases

  4. Flower petals: Some flowers like hydrangea, petunia, and geranium

    • Change color based on the acidity of the soil

Synthetic Indicators​

Scientists have created indicators in the laboratory:

  1. Phenolphthalein:

    • Colorless in acids
    • Pink in bases

  2. Methyl orange:

    • Red in acids
    • Yellow in bases

🎮 Fun Facts​

  • The word "acid" comes from the Latin word "acidus," which means "sour."
  • The word "alkali" (another name for bases) comes from Arabic "al qaliy," which means "the ashes." This is because ashes mixed with water feel slippery like soap.
  • Your stomach contains hydrochloric acid that helps digest food.
  • Honey is the only common food that contains naturally occurring acid (gluconic acid) but still tastes sweet, not sour!

🔄 Quick Activity: Make Your Own Indicator​

You can make a simple indicator at home:

  1. Take a small piece of turmeric or red cabbage
  2. Crush it and extract the juice
  3. Dip a white cotton cloth strip in this juice and let it dry
  4. Use these strips to test if substances are acidic or basic:
    • Lemon juice (acid)
    • Soap water (base)
    • Vinegar (acid)
    • Baking soda solution (base)

💡 Key Points to Remember​

  • Acids taste sour and turn blue litmus paper red
  • Bases taste bitter and turn red litmus paper blue
  • Natural indicators like litmus, turmeric, and red cabbage juice help identify acids and bases
  • Synthetic indicators like phenolphthalein and methyl orange are also used
  • Acids, bases, and salts are common in everyday life

🤔 Think About It!​

  1. Why do we use indicators instead of tasting substances to identify acids and bases?
  2. Can you think of other substances in your kitchen that might be acids or bases?
  3. How do you think our ancestors discovered acids and bases before modern science?

In the next section, we'll learn more about the chemical properties of acids and bases and how they behave with different substances.