The correct option for the question regarding which factor most significantly affects the electrical conductivity of gases at low pressures is **A. Temperature**. ### Detailed Explanation 1. **Understanding Electrical Conductivity in Gases**: - Electrical conductivity in gases refers to the ability of a gas to conduct electric current. This property is significantly influenced by the presence of charged particles (ions and electrons) in the gas. - At low pressures, gases are less dense, and the mean free path (the average distance a particle travels before colliding with another particle) is longer. This means that the behavior of the gas can be more easily influenced by external factors. 2. **Role of Temperature**: - **Temperature and Kinetic Energy**: As temperature increases, the kinetic energy of gas molecules also increases. This leads to more frequent and energetic collisions between gas molecules, which can result in the ionization of some molecules. - **Ionization**: Higher temperatures can provide enough energy to overcome the ionization energy of the gas molecules, creating more free electrons and positive ions. This increase in charged particles enhances the gas's ability to conduct electricity. - **Thermal Ionization**: At elevated temperatures, thermal ionization becomes significant, where gas molecules gain enough energy to lose electrons and form ions, thus increasing conductivity. 3. **Why Other Options Are Weaker**: - **B. Humidity**: While humidity can affect the conductivity of gases, especially in the context of air (where water vapor can contribute to ionization), it is not as significant a factor as temperature. In low-pressure conditions, the effect of humidity is less pronounced compared to the direct influence of temperature on molecular energy and ionization. - **C. Ionization Energy**: Ionization energy is a property of individual gas molecules and indicates how much energy is required to remove an electron from an atom or molecule. While it is important, it does not directly affect the overall conductivity of the gas in the same way that temperature does. Higher temperatures can help overcome the ionization energy barrier, thus making temperature a more significant factor. - **D. Molecular Weight**: The molecular weight of a gas can influence its density and mean free path, but it does not directly correlate with electrical conductivity. Lighter gases may have higher mobility, but without sufficient energy (temperature) to ionize, they will not conduct electricity effectively. ### Summary of Key Points - **Temperature** significantly affects the electrical conductivity of gases at low pressures by increasing molecular kinetic energy and promoting ionization. - **Humidity** can influence conductivity but is less significant than temperature in low-pressure scenarios. - **Ionization energy** is a property of the gas molecules but does not directly affect conductivity as temperature does. - **Molecular weight** affects density and mobility but does not directly correlate with conductivity without sufficient energy for ionization. ### Revision Summary - The most significant factor affecting electrical conductivity of gases at low pressures is **temperature**. - Increased temperature leads to higher kinetic energy, promoting ionization and increasing conductivity. - Humidity, ionization energy, and molecular weight are less significant in comparison to temperature. - Understanding the relationship between temperature and ionization is crucial for grasping gas conductivity behavior.