According to the kinetic molecular theory, in which of the following substances would the particles move most rapidly?

• A. Ice at 0 ^\circ C
• B. Steam at 120 ^\circ C
• C. Liquid water at 25 ^\circ C
• D. Liquid water at 100 ^\circ C

Answer: (B)

Verified step by step guidance

1. Recall that according to the kinetic molecular theory, the average kinetic energy of particles is directly proportional to the absolute temperature (in Kelvin). This means particles move faster at higher temperatures.
2. Convert all given temperatures from Celsius to Kelvin using the formula: \(T(K) = T(^\circ C) + 273.15\).
3. Compare the absolute temperatures of the substances: ice at 0 \(^\circ\)C, liquid water at 25 \(^\circ\)C, liquid water at 100 \(^\circ\)C, and steam at 120 \(^\circ\)C.
4. Understand that the phase (solid, liquid, gas) also affects particle movement, with gases generally having faster-moving particles than liquids or solids at the same temperature due to weaker intermolecular forces.
5. Conclude that the substance with the highest temperature in Kelvin and in the gas phase will have the most rapidly moving particles.