🧪
Chapter 9 – The Amazing
World of Solutes, Solvents, and Solutions
🌟 1. Mixtures: Uniform and
Non-uniform
🧠 Concept:
- When sugar/salt dissolves in water →
uniform mixture
- When sand/chalk/sawdust is mixed →
non-uniform mixture
🔹 Types:
✅ Uniform Mixture (Solution)
- Components not visible separately
👉 Example: Sugar in water
❌ Non-uniform Mixture
- Components visible separately
👉 Example: Sand in water
💧 2. Solute, Solvent, and
Solution
📌 Definitions:
🔹 Solute
- Substance that dissolves
- Usually in smaller quantity
🔹 Solvent
- Substance in which solute dissolves
- Usually in larger quantity
🔹 Solution
Uniform mixture of solute +
solvent
📍 Examples:
- Salt in water →
Salt = solute, Water = solvent
- Sugar syrup →
Sugar = solute, Water = solvent
- Air →
Nitrogen = solvent, others = solutes
🧂 3. How Much Solute Can
Dissolve?
🔄 Types of Solutions:
🔹 Unsaturated Solution
- More solute can dissolve
🔸 Saturated Solution
- No more solute dissolves
🔹 Concentrated Solution
- Large amount of solute
🔸 Dilute Solution
- Small amount of solute
📌 Solubility:
Maximum solute that dissolves
in given solvent at a specific temperature
🌡️ 4. Effect of Temperature
(Solids in Liquids)
📈 Rule:
- Solubility increases with temperature
📍 Example:
- Baking soda dissolves more in hot water
🧠 Important:
- Saturated solution →
becomes unsaturated on heating
🌬️ 5. Solubility of Gases in
Liquids
📌 Key Points:
- Gases (like oxygen) dissolve in water
- Important for aquatic life 🐟
🌡️ Effect of Temperature:
- Temperature ↑ →
gas solubility ↓
- Cold water →
more oxygen
- Warm water →
less oxygen
🌊 6. Floating and Sinking
❌ Myth:
“Heavier objects sink”
✅ Truth:
Depends on density
📍 Examples:
- Oil floats
- Sand sinks
⚖️ 7. Density
📌 Definition:
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= \frac{m}{V}"}}
📏 Units:
- SI: kg/m³
- Common: g/cm³, g/mL
🔄 Relative Density:
\text{Relative Density} =
\frac{\text{Density of substance}}{\text{Density of water}}
📌 Example:
- Aluminium = 2.7 →
2.7 times denser than water
⚖️ 8. Measuring Mass
📌 Mass:
- Amount of matter
📏 Units:
- kg, g
⚙️ Instruments:
- Digital balance
- Traditional balance
⚠️ Note:
- Mass ≠ Weight
⚖️ Difference: Mass vs Weight
|
Feature |
Mass |
Weight |
|
Meaning |
Matter |
Gravitational force |
|
Unit |
kg |
Newton (N) |
|
Change |
Same everywhere |
Changes |
📏 9. Measuring Volume
💧 Liquids:
- Use measuring cylinder
📌 Reading Rule:
- Read at bottom of meniscus
- For coloured liquids →
top
📦 Regular Solids:
V = l \times w \times h
🪨 Irregular Solids:
- Use water displacement method
👉 Volume of water displaced = volume of
object
🧮 10. Density Calculation
📌 Formula:
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= \frac{m}{V}"}}
📍 Example:
- Mass = 16.4 g
- Volume = 5 cm³
👉 Density = 3.28 g/cm³
🌡️ 11. Effect of Temperature on
Density
🔥 Heating:
- Particles move apart
- Volume ↑ →
Density ↓
❄️ Cooling:
- Particles come closer
- Volume ↓ →
Density ↑
🎈 Example:
- Hot air rises (less dense)
ضغط 12.
Effect of Pressure on Density
🌬️ Gases:
- Pressure ↑ →
particles closer → density ↑
🧱 Solids & Liquids:
- Hardly affected
🧊 13. Why Does Ice Float?
📌 Concept:
- Water highest density at 4°C
- On freezing →
expands → density decreases
👉 Ice becomes lighter → floats
🌊 Importance:
- Water below ice remains warm
- Helps aquatic life survive
🧠 14. Examples and Applications
🥚 Egg in Water:
- Normal →
sinks
- Salt water →
floats
🛢️ Oil:
- Less dense than water →
floats
🎋 Bamboo Rafts:
- Hollow →
float easily
🌍 Earth Layers:
- Density increases from crust →
core
📌 15. Snapshots (Quick Revision)
⚡ One-Line Points
- Solution = uniform mixture
- Solute = dissolving substance
- Solvent = medium
- Saturated →
no more dissolving
- Unsaturated →
can dissolve more
- Solubility:
- Solids ↑
with temperature
- Gases ↓
with temperature
- Density = mass ÷ volume
- Temperature ↑ →
density ↓
- Pressure affects gases most
- Ice floats due to lower density
🎯 Final Conclusion
Solutions and density explain
many real-life phenomena:
- Dissolving substances
- Floating & sinking
- Behavior of gases and liquids
🌟 Final Formula:
Density decides floating &
sinking
🧠 Learning Outcome:
- Understand solutions & solubility
- Calculate density
- Apply concepts in daily life
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