Learning Path
Question & Answer1
Understand Question2
Review Options3
Learn Explanation4
Explore TopicChoose the Best Answer
A
High temperature and high pressure
B
Low temperature and low pressure
C
Constant pressure at room temperature
D
Variable temperature at atmospheric pressure
Understanding the Answer
Let's break down why this is correct
Answer
A substance reaches its critical point when the temperature and pressure rise to the substance’s critical temperature and critical pressure, values that differ for each material. At that moment the liquid and gas phases become indistinguishable, forming a single, homogeneous fluid called a supercritical fluid. The reason is that the density difference between liquid and gas shrinks to zero, so no surface tension or latent heat exists. For example, water’s critical point is at about 374 °C and 22. 06 MPa, where water behaves neither as a liquid nor a vapor but as a dense, single phase.
Detailed Explanation
When a liquid is heated and pressurized enough, its molecules gain enough energy to move freely but stay close together. Other options are incorrect because Low temperature and low pressure keep molecules too far apart to merge phases; Constant pressure at room temperature cannot provide enough energy for molecules to behave like gas.
Key Concepts
Phases of Matter
Critical Point
Topic
States of Matter
Difficulty
medium level question
Cognitive Level
understand
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