The temperature of an object is raised by 120°C. The resulting increase in its absolute temperature is

Analyze the question The temperature rises by 120°C. We are asked for the corresponding increase on the absolute (Kelvin) scale. This is about a temperature change, not a temperature reading.

Concept The Celsius and Kelvin scales are related by:

T(K) = θ(°C) + 273

The two scales have the same size of degree, so one degree Celsius step equals one kelvin step. The only difference between them is where zero is placed.

Solution Suppose the initial temperature is θ₁ and the final temperature is θ₂, with θ₂ − θ₁ = 120°C.

In Kelvin:

• T₁ = θ₁ + 273
• T₂ = θ₂ + 273

Increase in absolute temperature: ΔT = T₂ − T₁ = (θ₂ + 273) − (θ₁ + 273) = θ₂ − θ₁ = 120 K

The 273 cancels out, so a change of 120°C is exactly a change of 120 K.

Answer The increase in absolute temperature is 120 K, which is option B.

Why the other options are wrong

• D (393 K) comes from adding 273 to 120. That would be the absolute temperature of an object at 120°C, not the increase in temperature.
• A and C do not match any correct calculation.

Exam tip When a question says "raised by," "increase in," or "change in" temperature, the number stays the same in °C and K. Only add 273 when the question gives an actual temperature reading, such as "at 120°C."