Internal energy and enthalpy depend solely on temperature for which of the following substances____________________?
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Answer: D. perfect gas
Explanation
Joule law states that the internal energy of a perfect gas is a function of temperature alone. Enthalpy is defined as internal energy plus the product of pressure and volume for the substance. Since the product of pressure and volume also depends solely on temperature, enthalpy shares this property. A perfect gas strictly obeys the ideal gas law equation of state across all temperature ranges. Molecular forces in an ideal gas are assumed to be negligible, meaning potential energy is zero. Internal energy changes for such gases can be calculated directly using constant specific heat values.
Option A is too broad because real gases exhibit pressure dependent internal energy at high densities. Option B involves saturated steam, which clearly depends on both pressure and temperature during phase changes. Option C involves liquid water, whose properties vary significantly with both pressure and temperature changes.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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