Liquid oxygen at 50 K is heated to 300 K at a constant pressure of 1 atm. The rate of heating is constant. Which of the following graphs represents the variation of temperature with time?
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Liquid oxygen at 50 K is heated to 300 K at a constant pressure of 1 atm. The rate of heating is constant. Which of the following graphs represents the variation of temperature with time?

G1 Physics · Accepted Answer

Step 1: The sample is initially a liquid; heating increases temperature until the boiling point at 1 atm is reached. Step 2: During boiling, added heat is used as latent heat of vaporisation, so the temperature remains constant for a finite time (horizontal plateau). Step 3: Once all liquid becomes gas, continued heating raises temperature again until 300 K. Step 4: Therefore the graph has an increasing segment, a horizontal plateau, then another increasing segment. Final answer: (A) the heatin…