Q1: With increase in temperature, the thermal conductivity of a gas

ANS:A - increases.

With an increase in temperature, the thermal conductivity of a gas typically increases. Here's why:

1. Increase in Molecular Velocity: As the temperature of a gas increases, the average kinetic energy of its molecules increases. This results in higher molecular velocities and more frequent collisions between molecules. These collisions enhance the transfer of thermal energy through the gas, leading to an increase in thermal conductivity.
2. Effect on Mean Free Path: While the mean free path of gas molecules tends to decrease with increasing temperature due to increased molecular collisions, the overall effect of increased molecular velocity dominates. This leads to an increase in thermal conductivity as more energy is transferred through the gas.
3. Temperature Dependence of Specific Heat Capacity: The specific heat capacity of gases tends to increase with temperature. This means that gases can store more thermal energy per unit temperature increase at higher temperatures, which can facilitate more efficient heat transfer and result in higher thermal conductivity.