Exploring Substances: Acidic, Basic, and Neutral
Introduction
- This chapter explains acidic, basic, and neutral substances.
- It begins with a science fair where a white paper revealed a message when sprayed with a liquid, sparking curiosity about substances that change color when mixed.
1. Nature – Our Science Laboratory
Litmus as an Indicator
1. What is Litmus?
- Litmus is a natural substance from lichens (fungus and alga combination).
- Available as blue and red paper strips or solution.
- It’s an acid-base indicator that changes color in acidic or basic solutions.
2. How it Works:
- Acidic substances (e.g., lemon juice, vinegar) turn blue litmus red.
- Basic substances (e.g., soap solution, lime water) turn red litmus blue.
- Neutral substances (e.g., tap water, sugar solution) don’t change litmus color.
3. Key Substances:
- Acidic: Lemon juice, amla juice, tamarind water, vinegar.
- Basic: Soap solution, baking soda solution, lime water, washing powder solution.
- Neutral: Tap water, sugar solution, salt solution.
4. Lime Water: Made by mixing calcium oxide (lime) with water, letting it sit, and filtering.
2. Red Rose as an Indicator
- Red Rose Extract:
- Acts as an acid-base indicator.
- Turns red in acidic solutions (e.g., lemon juice).
- Turns green in basic solutions (e.g., soap solution).
- No color change in neutral solutions.
Other Natural Indicators: Beetroot, purple cabbage, turmeric, Indian blackberry (jamun), red hibiscus.
Fascinating Fact:
- Hydrangea flowers change color based on soil:
- Acidic soil: Blue flowers.
- Basic soil: Pink or red flowers.
3. Turmeric as an Indicator
- Turmeric:
- Acts as an indicator for basic substances.
- Turns red in basic solutions (e.g., soap solution).
- Stays yellow in acidic or neutral solutions.
Fascinating Fact:
- Turmeric is a “Golden” spice used in food, Ayurvedic medicine, and known for health benefits.
Olfactory Indicators
- Substances like onions whose smell changes in acidic or basic conditions.
- Example: Onion smell changes differently with tamarind water (acidic) or baking soda (basic).
4.What Happens When Acidic and Basic Substances Mix?
- Neutralization Reaction:
- When an acid (e.g., lemon juice) and a base (e.g., lime water) mix in the right amounts, they form a neutral solution.
- Reaction: Acid + Base → Salt + Water + Heat.
- Example: Lemon juice (acidic) turns blue litmus red; adding lime water (basic) turns it blue again, showing neutralization.
5. Neutralization in Daily Life
Ant Bite:
- Ants inject formic acid, causing pain.
- Moist baking soda (base) neutralizes the acid, relieving pain.
Acidic Soil:
- Chemical fertilizers can make soil acidic, harming plants.
- Lime (base) neutralizes acidic soil.
- Basic soil is treated with organic matter (e.g., manure) to release acids.
Industrial Waste:
- Acidic factory waste harms aquatic life.
- Adding basic substances neutralizes waste before release.
6.Science Fair Mystery
- A paper showed the message “Welcome to the Wonderful World of Science” when sprayed.
- Explanation: Likely written with a basic solution (e.g., soap solution) on turmeric-coated paper. Spraying turmeric solution turned basic areas red, revealing the message.
7. Key Points
- Substances are acidic, basic, or neutral.
- Indicators identify substance nature:
- Litmus: Blue to red (acids), red to blue (bases).
- Red rose extract: Red (acids), green (bases).
- Turmeric: Red (bases), yellow (acids/neutral).
- Olfactory indicators (e.g., onion): Smell changes in acidic/basic conditions.
- Acids: Taste sour (e.g., lemon, vinegar), contain acids like citric, tartaric.
- Bases: Feel slippery, taste bitter (e.g., baking soda, soap).
- Neutral substances: No effect on indicators (e.g., sugar, salt).
- Neutralization: Acid + base forms salt, water, and heat.
- Neutralization is used for ant bites, soil treatment, and waste management.
8.Common Acids in Edible Substances
- Lemon: Citric acid
- Curd: Lactic acid
- Tamarind: Tartaric acid
- Vinegar: Acetic acid
9. Know a Scientist
Acharya Prafulla Chandra Ray:
- “Father of Modern Indian Chemistry”.
- Earned a UK doctorate, advanced Indian scientific research.
- Founded India’s first pharmaceutical company (1901).
- Promoted Indian culture and mother tongue in education.
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