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 Certainly, Mayank! Here's the final enriched explanation of Melting Point, now including the concept of Latent Heat of Fusion along with temperature conversion, real-life examples, and everything needed for a clear, engaging Class 9 lecture.

🧊 Melting Point (Class 9 – CBSE Science)

📘 Definition of Melting Point:

The melting point of a substance is the temperature at which it changes from a solid to a liquid at atmospheric pressure.

✅ At this temperature, the solid and liquid states coexist in equilibrium.

🔬 What Happens During Melting?

  • As a solid is heated, its particles gain kinetic energy.

  • They begin to vibrate faster, weakening the inter-particle attraction.

  • At a certain temperature, particles break free from fixed positions and the substance melts into a liquid.

  • The temperature stays constant during this process, even though heat is still being supplied.

⚡ Latent Heat of Fusion

📘 Definition:

Latent heat of fusion is the amount of heat energy required to change 1 kg of a solid into liquid at its melting point without any change in temperature.

💡 Example:

  • When ice melts at 0°C (273 K), it absorbs latent heat from its surroundings.

  • This energy is hidden (latent) and goes into breaking the bonds between particles, not increasing temperature.

🔁 This is why ice feels extra cold — it absorbs a lot of heat from your hand to melt, even without getting warmer!

🧪 Common Melting Point Examples:

Substance Melting Point (°C) Melting Point (K)
Ice (H₂O) 0°C 273 K
Wax ~60°C 333 K
Iron 1538°C 1811 K
Gold 1064°C 1337 K

📎 Note on Temperature Conversion

📘 Kelvin is the SI unit of temperature.
Here's how to switch between °C and K:

To Convert Formula Example
°C → K K = °C + 273 0°C = 273 K
K → °C °C = K – 273 373 K = 100°C
Exact value (for accuracy) 0°C = 273.15 K Rounded as 273 K

📘 CBSE Link:

"Melting point tells us about the strength of force of attraction between particles in a solid.
Higher melting point = stronger bonding between particles."

💬 Ask Your Students:

  1. What is the melting point of ice in °C and K?

  2. Why does temperature remain constant while ice melts?

  3. Define latent heat of fusion in your own words.

  4. Why do we use Kelvin in science?

🎤 Closing Line for Class:

“Melting is not just about heat — it’s a battle between energy and attraction. When particles win that battle, they flow — and science calls it fusion.”

Would you like this formatted into a smartboard slide, printable PDF, or flashcards for classroom revision?


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