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Difficulty: MediumPostulates of Kinetic Theory and States of Matter

Based on the kinetic molecular theory of matter, which of the following best explains why liquids have a fixed volume but take the shape of their container?

  1. A
    The particles are tightly fixed in rigid positions and can only vibrate about fixed axes.
  2. B
    The particles have negligible intermolecular forces and move completely independently to fill all available space.
  3. The particles are close together with moderate intermolecular attractive forces, allowing them to slide past one another while remaining bound in volume.Answer
  4. D
    The average kinetic energy of liquid particles is zero at room temperature, preventing thermal movement.

Answer

The particles are close together with moderate intermolecular attractive forces, allowing them to slide past one another while remaining bound in volume.
According to the kinetic theory, liquid particles are held closely by intermolecular forces, maintaining a definite volume, but possess enough kinetic energy to slide over one another, enabling the liquid to flow and take the shape of its container.

Step-by-Step Solution

1
Analyze the microscopic properties of the liquid state according to kinetic molecular theory.
Liquid particles possess intermediate kinetic energy compared to solids and gases.
Understanding the balance between kinetic energy and intermolecular forces explains liquid behavior.
2
Relate particle arrangement to volume and shape characteristics.
Moderate intermolecular forces keep the particles close together (definite volume), but allow them to slide past each other dynamically (indefinite shape).
Fluidity requires movement between particles, while fixed volume requires persistent intermolecular contacts.

Key Concept

Kinetic Molecular Postulates and States of Matter
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Topics

Postulates of Kinetic Theory and States of Matter