Which one of the following elements exists in liquid state at room temperature?

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Q: 83 (NDA-II/2009)

Which one of the following elements exists in liquid state at room temperature?

question_subject: 

Science

question_exam: 

NDA-II

stats: 

0,49,3,49,0,1,2

keywords: 

{'liquid state': [0, 0, 1, 1], 'elements': [0, 0, 2, 5], 'mercury': [0, 0, 2, 2], 'sodium': [10, 2, 12, 23], 'calcium': [2, 0, 0, 4], 'room temperature': [0, 0, 5, 6], 'lead': [7, 1, 11, 11]}

The correct answer is option 1: Mercury.

Mercury is the only element among the options provided that exists in liquid state at room temperature. Mercury is a unique element because it has a very low melting point of -38.83 degrees Celsius (-37.89 degrees Fahrenheit) and boiling point of 356.73 degrees Celsius (674.11 degrees Fahrenheit). This means that even at room temperature (typically around 20-25 degrees Celsius), mercury remains in a liquid state.

On the other hand, the other elements listed in the options (lead, sodium, and calcium) exist as solids at room temperature. Lead has a melting point of 327.5 degrees Celsius (621.5 degrees Fahrenheit), sodium has a melting point of 97.72 degrees Celsius (207.9 degrees Fahrenheit), and calcium has a melting point of 842 degrees Celsius (1548 degrees Fahrenheit). Therefore, at room temperature, these elements are in solid form.

In summary, mercury is the only element among the options that exists in a liquid state at room temperature.