PREVIOUSLY ASKED IN:
WBPSC Miscellaneous Preliminary 2019
Answer
molecules have intermolecular forces.
Explanation
When a gas is kept below its critical temperature and compressed, it liquefies. The compression brings the gas molecules closer together, which significantly increases the intermolecular forces of attraction between them. Once these forces become strong enough to overcome the kinetic energy of the molecules, the gas changes into a liquid state. Above the critical temperature, a gas cannot be liquefied no matter how much pressure is applied.
Key Points
- > Critical temperature is the highest temperature at which a gas can be liquefied by pressure alone.
- > The critical temperature of Carbon Dioxide is 31.1°C.
- > The intermolecular forces responsible for liquefaction are often referred to as Van der Waals forces.
- > Both increasing pressure and decreasing temperature favor the liquefaction of gases.
- > In the kinetic theory of ideal gases, intermolecular forces are assumed to be zero, but they exist in real gases.
Additional Information
States of Matter & Properties
| State | Molecular Arrangement | Intermolecular Force |
|---|---|---|
| Solid | Tightly packed | Strongest |
| Liquid | Loosely packed | Moderate |
| Gas | Very loosely packed | Weakest |
| Plasma | Ionized state | Affected by magnetic fields |
Memory Tips
- Solid to Gas: Temperature increases, intermolecular force decreases.
- Gas to Liquid: Pressure increases, intermolecular force increases.
- Critical Temp (Tc): The temperature above which liquefaction is impossible.