At what temperature does water transform into steam under normal atmospheric pressure?  

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RRB Technician Grade III Official Paper (Held On: 28 Dec, 2024 Shift 3)
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  1. 100°C (212°F) 
  2. 50°C (122°F)  
  3. 80°C (176°F) 
  4. 0°C (32°F) 

Answer (Detailed Solution Below)

Option 1 : 100°C (212°F) 
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Detailed Solution

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The Correct answer is 100ºC (212ºF).

Key Points

  • Water transforms into steam at a temperature of 100ºC (212ºF) under normal atmospheric pressure, which is approximately 1 atm (101.325 kPa).
  • This process is called boiling, and it occurs when the vapor pressure of water equals the atmospheric pressure.
  • At the boiling point, water molecules gain enough kinetic energy to overcome intermolecular forces and transition from the liquid phase to the gaseous phase.
  • The boiling point of water can vary depending on altitude and pressure. At higher altitudes where pressure is lower, water boils at a temperature below 100ºC.
  • This temperature is widely used in science, cooking, and industrial applications to measure and control heat processes.
  • The boiling point of water is a crucial reference point in the Celsius temperature scale, where it is defined as 100ºC.

 Additional Information

  • 50ºC (122ºF)
    • This temperature is far below the boiling point of water under normal atmospheric pressure.
    • At 50ºC, water remains in the liquid state and is often considered warm but not hot enough for steam formation.
    • This temperature is commonly used in applications like heating water for bathing or other domestic uses.
  • 80ºC (176ºF)
    • 80ºC is still below the boiling point of water.
    • Water at this temperature is considered hot and is often used in cooking or beverage preparation, like making tea or coffee.
    • At this temperature, water may begin to exhibit signs of evaporation, but it does not boil or turn into steam under normal atmospheric pressure.
  • 0ºC (32ºF)
    • This is the freezing point of water under normal atmospheric pressure, not the boiling point.
    • At 0ºC, water transitions from a liquid to a solid, forming ice.
    • This temperature is a key reference in the Celsius and Fahrenheit scales.
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