Question

question 2
which statement best describes the motion of gas particles?
they move quickly in all directions and are far apart
they stay still and form clusters
they slide past each other but stay close
they vibrate in a fixed position
question 3
why does a solid expand when heated?
the solid gains weight from added heat
the particles move faster and take up more space
the atoms form new bonds and split
the molecules are replaced by air

Explanation:

• Question 2: According to the kinetic - molecular theory of gases, gas particles have high kinetic energy. They move rapidly in all directions and are far apart from each other. Particles that stay still and form clusters (\(2^{nd}\) option) is more like a description of a non - ideal solid or a very condensed and non - moving state which is not gas. Particles that slide past each other but stay close (\(3^{rd}\) option) is a description of liquid particles. Particles that vibrate in a fixed position (\(4^{th}\) option) is a description of solid particles.
• Question 3: When a solid is heated, the thermal energy is transferred to the particles (atoms/molecules). The particles gain kinetic energy and move faster. As they move faster, the average distance between them increases, and they take up more space (thermal expansion). A solid does not gain weight from added heat ( \(1^{st}\) option, heat is energy, not mass in the context of simple heating and expansion). Atoms do not form new bonds and split in the simple heating and expansion of a solid ( \(3^{rd}\) option, this would be more like a chemical reaction). Molecules are not replaced by air ( \(4^{th}\) option, air molecules would not replace the solid's molecules during simple heating and expansion).

Answer:

• Question 2: They move quickly in all directions and are far apart
• Question 3: The particles move faster and take up more space