FISIKA KELAS XI | TEORI KINETIK GAS (PART 3) - Tekanan dan Energi Gas Ideal

Summary

In this video, Yusuf Armada explains key concepts from the kinetic theory of gases, focusing on pressure and kinetic energy of ideal gases. He details the mathematical formulas for calculating pressure (P = 1/3 nmv²) and kinetic energy (E = 1/2 mv²), showing how they relate to molecular motion. Through practical examples, he demonstrates how to calculate pressure in a gas-filled container and the average kinetic energy of gas molecules at various temperatures. The video is an engaging tutorial for high school students studying physics, with clear explanations and step-by-step calculations.

Takeaways

• 😀 The video discusses the topic of pressure and kinetic energy in ideal gases, specifically focusing on the equations and concepts from kinetic gas theory.
• 😀 The formula for the pressure of an ideal gas is introduced as P = (1/3) * n * m * v^2, where P is the pressure in Pascal, n is the number of particles, m is the mass of the gas molecules, and v is the average speed of gas particles.
• 😀 The relationship between kinetic energy and pressure is explained, with the kinetic energy formula (1/2) * m * v^2, where E_k is the kinetic energy of the gas particles in Joules.
• 😀 The video demonstrates how to substitute the formula for kinetic energy (1/2) * m * v^2 = E_k into the pressure equation, resulting in P = (2/3) * n * E_k / V.
• 😀 A worked example is provided to calculate the pressure of a gas inside a container, using the known values for the number of moles, volume, and kinetic energy.
• 😀 The number of particles (N) in a gas is calculated using N = n * N_A, where n is the number of moles and N_A is Avogadro's number, leading to a result of 1.80 × 10^23 particles.
• 😀 The example shows how to convert the given volume from liters to cubic meters (24 L = 0.024 m³) to correctly calculate the pressure in SI units.
• 😀 The final pressure calculation yields a result of 1.50 × 10^5 Pascals, demonstrating the application of the ideal gas equations.
• 😀 The script then shifts to discussing the energy of an ideal gas in terms of temperature, referencing the ideal gas law PV = nRT.
• 😀 The video introduces the formula for the average kinetic energy of an ideal gas: E_k = (3/2) * k_B * T, where k_B is the Boltzmann constant and T is the temperature in Kelvin. A second example calculates the kinetic energy of a helium gas at 127°C (400K), yielding 8.8 × 10^-21 Joules.

Q & A

What is the formula for the pressure of an ideal gas?

The formula for the pressure of an ideal gas is: P = (1/3) * n * m * v^2, where P is the pressure in Pascal (Pa), n is the number of particles, m is the mass of a gas molecule, and v is the average velocity of the gas molecules.

How is kinetic energy related to the gas pressure formula?

The kinetic energy of the gas molecules is given by X = (1/2) * m * v^2. By substituting this into the pressure formula, the pressure expression becomes P = (2/3) * n * Eka / V, where Eka is the average kinetic energy of the gas molecules.

What is the relationship between pressure, volume, and temperature in ideal gases?

According to the ideal gas law, PV = nRT, where P is pressure, V is volume, n is the number of moles, R is the universal gas constant, and T is the temperature in Kelvin.

How do you calculate the total number of gas molecules from moles?

The total number of gas molecules (N) can be calculated by multiplying the number of moles (n) by Avogadro's number (Na), which is approximately 6.02 × 10^23. The formula is N = n * Na.

What is the value of Boltzmann's constant?

Boltzmann's constant (k) is 1.38 × 10^-23 J/K, and it relates the average kinetic energy of particles to the temperature in Kelvin.

How do you convert the temperature from Celsius to Kelvin?

To convert temperature from Celsius to Kelvin, simply add 273 to the Celsius temperature. For example, 127°C equals 400 K.

How do you calculate the kinetic energy of a gas at a given temperature?

The average kinetic energy (Eka) of a gas can be calculated using the formula: Eka = (3/2) * k * T, where k is Boltzmann's constant and T is the temperature in Kelvin.

What is the energy of one gas molecule in the given example with helium?

In the example, the energy of one helium molecule at 127°C (400 K) is approximately 8.8 × 10^-21 Joules, calculated using the formula Eka = (3/2) * k * T.

How do you find the pressure of a gas when given the number of moles, volume, and kinetic energy?

You can calculate the pressure using the formula: P = (2/3) * n * Eka / V, where n is the number of moles, Eka is the average kinetic energy, and V is the volume.

What happens to the pressure if the volume of the gas increases while keeping the kinetic energy constant?

If the volume increases while keeping the kinetic energy constant, the pressure decreases, because pressure is inversely proportional to volume (P = n * Eka / V).