Which among the following is/are the reasons behind using Mercury in thermometers ? 1. Mercury does not wet the inner sides of the thermometer. 2. It can be seen easily in a thin capillary tube of the thermometer. 3. It is a good conductor of heat. 4. It is non-toxic. Select the correct answer using the code given below :

Mercury is used in thermometers due to several distinct physical properties. First, it does not wet the inner glass surface of the thermometer because its cohesive forces are stronger than its adhesive forces with glass [t3, t4]. This prevents streaks and ensures a clear, accurate reading [t3]. Second, as a liquid metal, it is opaque and shiny, making it easily visible within a thin capillary tube [t1, t5]. Third, mercury is a good conductor of heat, which allows it to respond quickly to temperature changes [c2]. However, statement 4 is incorrect; mercury is highly toxic and poses significant risks to human health and the environment, as highlighted by the Minamata Convention [c1, c4, t6]. Therefore, only statements 1, 2, and 3 are valid reasons for its use in thermometry.

Sources

1. [1] https://www.sciencedirect.com/topics/engineering/mercury-column
2. [2] Science-Class VII . NCERT(Revised ed 2025) > Chapter 4: The World of Metals and Non-metals > Table 4.1: Appearance, hardness, and eff ect of hammering on diff erent objects or materials > p. 43
3. [3] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > 29.r.4. Mercury > p. 413
4. [4] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 28: International Organisation and Conventions > 28.22. MINAMATA CONVENTION > p. 411