Grade 10 SCIENCE | Quarter 4 Module 2 | Kinetic Molecular Theory, Avogadro's Law and Ideal Gas Law

Kinetic Molecular Theory (KMT)

Definition: KMT helps explain how gases behave at the tiny, molecular level.

Key Points:

• Molecular Composition: Gases are made up of molecules that are far apart.

• Molecular Motion: Molecules move around randomly and bump into each other without losing energy, like balls in a game.

• Negligible Intermolecular Forces: The tiny forces between gas molecules are very weak, making calculations easier.

• Kinetic Energy and Temperature Relationship: The average energy of gas molecules relates to temperature—faster molecules mean higher temperatures, slower ones mean lower temperatures.

Gas Laws

Avogadro's Law

Overview: This law connects the number of gas molecules to its volume. They are directly proportional if pressure and temperature stay the same.

Formula: V1/N1 = V2/N2 (V is volume, N is moles).

Examples:

• Example 1: If 1.2 L of gas has 0.07 moles (this is V1 and N1), then in a 20 L volume (V2), there would be about 1.17 moles.

• Example 2: For 47.6 moles in 3.80 L, if we want to find the volume for 73 moles, it results in approximately 5.83 L.

Ideal Gas Law

Definition: This law combines different gas laws into one: PV = nRT. Where:

• P = pressure (in atm)

• V = volume (in liters)

• n = number of moles

• R = universal gas constant (0.0821 L·atm/mol·K)

• T = temperature (in Kelvin)

Important: Use correct units for each variable to get accurate results!

Examples:

• Example 1: If P = 2.9 atm, V = 6.5 L, and T = 27°C (which is 300.15 K), then n is around 0.76 moles.

• Example 2: For 0.654 moles of neon gas in 15.2 L at 1.95 atm, using the ideal gas law gives a temperature of about 552 K.

Conclusion

Summary: Knowing KMT helps understand how gases act. Avogadro's law and the ideal gas law give us easy formulas to relate gas properties.