**Correct Option: B. Gas particles are far apart and move freely at high speeds.** ### Detailed Explanation: To understand why option B is the correct answer, we need to compare the behavior of particles in gases with those in solids. 1. **Particle Arrangement in Solids vs. Gases:** - In solids, particles are closely packed together in a fixed arrangement. They vibrate in place but do not move freely. This close packing gives solids a definite shape and volume. - In contrast, gas particles are much farther apart compared to solids. They do not have a fixed arrangement and can move freely in all directions. This is due to the high kinetic energy of gas particles, which allows them to overcome the attractive forces that hold them together in solids. 2. **Movement of Particles:** - In solids, the particles can only vibrate around their fixed positions. This limited movement is why solids maintain a definite shape and volume. - Gas particles, however, move at high speeds and can collide with each other and the walls of their container. This movement is random and allows gases to expand to fill the entire volume of their container, leading to no definite shape or volume. 3. **Kinetic Molecular Theory:** - The behavior of gas particles can be explained by the kinetic molecular theory, which states that: - Gas particles are in constant, random motion. - The average kinetic energy of gas particles is directly proportional to the temperature of the gas. - There are negligible forces of attraction between gas particles, allowing them to move freely and occupy more space. ### Why the Other Options are Incorrect: - **Option A: Gas particles are closely packed and vibrate in fixed positions.** - This statement describes the behavior of particles in a solid, not a gas. Gas particles are not closely packed; they are far apart and do not vibrate in fixed positions. - **Option C: Gas particles have a definite shape and volume.** - This is also incorrect. Gases do not have a definite shape or volume. They take the shape of their container and can expand to fill any volume available to them. - **Option D: Gas particles are arranged in a regular geometric pattern.** - This statement is true for solids, where particles are arranged in a regular, repeating pattern (like a crystal lattice). Gas particles, however, are arranged randomly and do not form any geometric pattern. ### Summary of Key Points: - Gas particles are far apart and move freely at high speeds, allowing them to fill the volume of their container. - In contrast, solid particles are closely packed and vibrate in fixed positions, giving solids a definite shape and volume. - The kinetic molecular theory explains the behavior of gas particles, emphasizing their constant motion and negligible intermolecular forces. - Understanding the differences in particle behavior between solids and gases is crucial for grasping fundamental concepts in chemistry. This thorough understanding of gas behavior compared to solids is essential for mastering concepts in physical chemistry and preparing for professional exams.