沸点
At the end of this lab, students should know...
化合物的沸点是什么？
化合物的沸点是指其从液态转变为气态时的温度。当溶液的蒸气压等于大气压时，便发生这一转变。
什么是蒸气压？
蒸气压是指在密闭系统中达到平衡时，化合物气相对其液相施加的压力。
分子间作用力如何影响沸点？
分子间作用力的类型和强度决定了破坏这些吸引力所需的能量。因此，能够形成氢键的化合物比仅通过伦敦色散力相互作用的化合物具有更高的沸点。
挥发性如何影响沸点？
挥发性是指化合物自发汽化的倾向。物质的挥发性越强，其沸点越低。
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实验室支架5
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温度计夹5
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数字温度计（60 -150ºC 范围）5
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玻璃毛细管20
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橡皮筋5
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试管 （3 -5 mm）10
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1 mL 玻璃移液器10
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移液器球10
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丙酮（纯度 99.5%>）10 mL
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乙醇（纯度 99.5%）10 mL
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25 mL 玻璃烧杯5
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250 mL 玻璃烧杯5
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搅拌热板5
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25 mL 带盖玻璃瓶2
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粉末漏斗2
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数字气压计1
来源：美国马萨诸塞大学阿默斯特分校 Lara Al Hariri
- 实验室准备
此处展示的是供10名学生（两人一组）进行实验的准备工作，并预留了一些余量。请根据需要调整用量。
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穿戴必要的个人防护装备，包括实验服、防化学飞溅护目镜和手套。
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学生在实验中将使用丙酮和乙醇。用溶剂名称标记一个玻璃瓶，然后从原装瓶中倒入少量溶剂至该玻璃瓶中，确保每组大约有1 mL的用量。对另一种溶剂进行相同操作，然后将这些瓶子放置于公共通风橱内。
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在每个学生实验台放置以下玻璃器皿和设备（建议学生两人一组操作）：
1 铁架台 1 加热板 1 升降台 1 橡胶圈 1 中号三指夹 3-4 玻璃毛细管 1 移液球 2 1-mL 移液管 2 玻璃试管 1 250-mL 烧杯 1 25-mL 烧杯 1 数字温度计
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Q1: What personal protective equipment is required for a boiling points lab?
Students must wear a lab coat, chemical splash goggles, and gloves before beginning work. These items protect against solvent exposure and potential chemical splashes during the experiment. Ensure all equipment is properly fitted and in good condition before starting the lab session.
Q2: How should solvents be prepared and distributed for a boiling points experiment?
Label glass bottles with solvent names, then transfer smaller volumes from stock bottles into labeled containers, allocating approximately 1 mL per student group. Place prepared solvent bottles in a communal hood to ensure proper ventilation and safety during the experiment.
Q3: What glassware is needed at each student lab station for measuring boiling points?
Each station requires two 1-mL volumetric pipettes for precise liquid measurement and two glass test tubes for holding samples during heating. Additional glassware includes a 250-mL beaker and a 25-mL beaker for preparation and mixing tasks. These tools enable accurate volume control and safe handling of liquids.
Q4: Why are glass capillary tubes used in boiling point experiments?
Glass capillary tubes are essential for observing boiling behavior at the microscopic scale during solvent heating. Three to four tubes per station allow students to monitor solvent boiling points accurately and safely while minimizing sample volume requirements and enabling precise temperature observations.
Q5: What heating equipment is required for a boiling points lab setup?
Each student pair needs a hotplate for controlled heating, a lab jack to adjust sample height, and a lab stand with a medium 3-prong clamp to secure test tubes during the experiment. A rubber band provides additional stability for glassware during heating and temperature measurement.
Q6: How should a digital thermometer be used in boiling point determination?
A digital thermometer measures the temperature at which solvents transition from liquid to vapor during heating. Position the thermometer bulb at the level of the boiling liquid inside the test tube to record accurate boiling point values for acetone and ethanol samples.
Q7: How should lab stations be organized for a boiling points experiment with multiple student pairs?
Arrange each station with a hotplate, lab stand, and clamp in a logical sequence for safe heating and observation. Include a pipette bulb for solvent transfer and ensure adequate spacing between stations. This organization allows pairs to work independently while maintaining safety and preventing cross-contamination.