To determine the correct answer regarding the contents of the portions P, Q, and R in a maximum and minimum thermometer, let's first understand how these thermometers work and the materials typically used in them. ### Understanding Maximum and Minimum Thermometers A maximum and minimum thermometer is designed to measure the highest and lowest temperatures over a certain period. It typically consists of a glass tube containing a liquid (usually alcohol or mercury) and a mechanism that records the maximum and minimum temperatures. 1. **Maximum Thermometer**: This part of the thermometer usually contains mercury or alcohol. When the temperature rises, the liquid expands and moves up the tube. A small constriction in the tube prevents the liquid from returning to its original position, thus marking the maximum temperature. 2. **Minimum Thermometer**: This part usually contains alcohol, which is less dense than mercury and has a lower freezing point. When the temperature drops, the alcohol contracts and leaves a mark at the lowest point it reaches. ### Analyzing the Options Now, let's analyze the options provided: - **Option A: Alcohol, mercury, and alcohol** - **Option B: Air, alcohol, and mercury** - **Option C: Mercury, alcohol, and mercury** - **Option D: Air, mercury, and alcohol** ### Evaluating Each Option 1. **Option A: Alcohol, mercury, and alcohol** - **Correctness**: This option is correct. In a typical maximum and minimum thermometer: - **P** (the maximum part) contains **mercury** because it is effective for measuring high temperatures. - **Q** (the minimum part) contains **alcohol** because it can measure lower temperatures without freezing. - **R** (the reservoir or the part that allows for expansion) also contains **alcohol** to ensure that the liquid can expand and contract effectively. 2. **Option B: Air, alcohol, and mercury** - **Incorrectness**: This option is incorrect because air cannot be used as a liquid in a thermometer. Thermometers require a liquid that expands and contracts with temperature changes, and air does not fulfill this requirement. 3. **Option C: Mercury, alcohol, and mercury** - **Incorrectness**: This option is incorrect because while mercury is used for maximum temperature measurement, the minimum part must be alcohol. Using mercury in both parts would not allow for accurate minimum temperature readings. 4. **Option D: Air, mercury, and alcohol** - **Incorrectness**: Similar to option B, this option is incorrect because it includes air, which cannot be used as a liquid in a thermometer. The presence of mercury in the maximum part is correct, but the inclusion of air makes this option invalid. ### Summary of the Correct Answer - **Final Answer**: **A. Alcohol, mercury, and alcohol** - **Explanation**: The maximum thermometer uses mercury to record high temperatures, while the minimum thermometer uses alcohol to record low temperatures. The design of the thermometer requires alcohol in the minimum section to ensure it can measure low temperatures effectively. ### Revision Summary - Maximum and minimum thermometers use different liquids for measuring temperature extremes: mercury for maximum and alcohol for minimum. - Air cannot be used in thermometers as it does not expand and contract like liquids. - The correct configuration for a maximum and minimum thermometer is typically mercury in the maximum section and alcohol in the minimum section. - Understanding the properties of the liquids used is crucial for identifying the correct answer in thermometer-related questions.