🌟 Class
7 Science Curiosity – Chapter 2 Notes
🧪
Exploring Substances: Acidic, Basic, and Neutral | Amresh
Academy
📘
Introduction
This chapter explains acidic, basic, and neutral
substances 🧪
👉 It
begins with a science fair experiment where a hidden message appeared
due to a chemical reaction, creating curiosity about indicators.
🌿 1.
Nature – Our Science Laboratory
🔴 Litmus
as an Indicator
📌 What
is Litmus?
- Natural
substance from lichens (fungus + algae)
- Available
as:
- Blue
paper 🔵
- Red
paper 🔴
- Used
as an acid-base indicator
⚡ How it
Works:
- 🍋 Acidic
substances → Blue litmus turns red
- 🧼 Basic
substances → Red litmus turns blue
- 💧 Neutral
substances → No change
🧪
Examples:
🔴 Acidic:
- Lemon
juice
- Amla
juice
- Tamarind
water
- Vinegar
🔵 Basic:
- Soap
solution
- Baking
soda
- Lime
water
- Washing
powder
⚪ Neutral:
- Tap
water
- Sugar
solution
- Salt
solution
🧱 Lime
Water:
- Made
from calcium oxide + water
- Allowed
to settle and filtered
🌹 2. Red
Rose as an Indicator
🌸 Red
Rose Extract:
- Works
as natural indicator
👉 Color
changes:
- Acid
→ Red
🔴
- Base
→ Green
🟢
- Neutral
→
No change
🌿 Other
Natural Indicators:
- Beetroot
- Purple
cabbage
- Turmeric
- Jamun
- Hibiscus
🌺
Fascinating Fact:
👉 Hydrangea
flower color changes:
- Acidic
soil → Blue 🌸
- Basic
soil → Pink/Red 🌸
🟡 3.
Turmeric as an Indicator
🧠
Properties:
- Turns
red in basic solutions 🔴
- Remains
yellow in acidic/neutral 🟡
🌟 Fact:
👉
Turmeric is a “Golden Spice”
- Used
in food 🍛
- Ayurvedic
medicine 🌿
👃
Olfactory Indicators
👉
Substances whose smell changes
Example:
- Onion
smell changes with:
- Acid
(tamarind)
- Base
(baking soda)
⚖️ 4.
Neutralization Reaction
🧪
Definition:
👉 When acid
+ base combine → neutral solution
📌
Reaction:
👉 Acid +
Base → Salt +
Water + Heat
💡
Example:
- Lemon juice (acid) + Lime water (base)👉 Forms neutral solution
🏠 5.
Neutralization in Daily Life
🐜 Ant
Bite:
- Contains
formic acid
- Baking
soda (base) neutralizes it
🌱 Soil
Treatment:
- Acidic
soil → add lime
- Basic
soil → add organic matter
🏭
Industrial Waste:
- Acidic waste treated with bases👉 Protects aquatic life
🎭 6.
Science Fair Mystery
👉 Hidden
message appeared due to turmeric indicator
🧠
Explanation:
- Written
with base (soap solution)
- Sprayed with turmeric → turns red👉 Message becomes visible
📌 7. Key
Points
- Substances
are:
- Acidic
🔴
- Basic
🔵
- Neutral
⚪
🧪
Indicators:
- Litmus
→
Red/Blue change
- Red
rose → Red/Green
- Turmeric
→
Yellow/Red
- Olfactory
→
Smell change
🍋
Properties:
- Acids
→
Sour taste
- Bases
→
Bitter + slippery
- Neutral
→
No effect
⚖️
Neutralization:
👉 Acid +
Base → Salt +
Water + Heat
🍋 8.
Common Acids in Food
|
Food Item |
Acid |
|
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 🇮🇳
- Studied
in UK 🎓
- Founded
India’s first pharma company (1901)
- Promoted
Indian culture & education
📌 Final
Summary
👉 This
chapter helps you understand:
- Acids,
bases & neutral substances 🧪
- Indicators
🌿
- Neutralization
⚖️
- Daily
life applications 🌍
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