The correct option for the question regarding which factor primarily 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**: When gas molecules gain enough energy (due to increased temperature), they can lose electrons and become positively charged ions. This process increases the number of charge carriers (ions and electrons) in the gas, thereby enhancing its electrical conductivity. - **Thermal Ionization**: At higher temperatures, thermal ionization becomes significant, where the thermal energy of the gas molecules is sufficient to ionize them, contributing to 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 the primary factor at low pressures. In low-pressure environments, the effect of humidity is less pronounced compared to temperature, which directly influences the energy of the gas molecules. - **C. Ionization Energy**: Ionization energy is the energy required to remove an electron from an atom or molecule. While it is a fundamental property of the gas, it does not directly affect conductivity in the same way that temperature does. Instead, it determines how easily a gas can be ionized, but the actual ionization and resulting conductivity are more influenced by the thermal energy provided by temperature. - **D. Molecular Weight**: The molecular weight of a gas can influence its density and the speed of its molecules, but it does not have a direct impact on conductivity at low pressures. Lighter gases may move faster, but without sufficient energy (from temperature), they will not ionize effectively. Thus, molecular weight is a secondary factor compared to temperature. ### Summary of Key Points - **Electrical conductivity in gases is primarily influenced by the presence of charged particles, which are affected by temperature.** - **Higher temperatures increase the kinetic energy of gas molecules, leading to more ionization and thus higher conductivity.** - **Humidity, ionization energy, and molecular weight play roles but are not as significant as temperature in low-pressure conditions.** ### Revision Summary - **Temperature is the primary factor affecting electrical conductivity of gases at low pressures.** - **Increased temperature leads to higher kinetic energy and more ionization of gas molecules.** - **Humidity, ionization energy, and molecular weight are less significant in this context.** - **Understanding the relationship between temperature and conductivity is crucial for analyzing gas behavior in low-pressure environments.**