Question

synthesize it!
select the correct statement(s).
the particles of a gas are at a higher temperature than its solid or liquid form. they have more kinetic energy. they have a lower density.
particle motion increases as temperature goes up.
all forms of a pure substance are affected by changes in temperature. only the gas form is affected by changes in volume and pressure.
the particles of a liquid are at a higher temperature than its gas form. they have more kinetic energy. they have a greater density.
the particles of a solid are at a lower temperature than its liquid or gas form. they have less kinetic energy. they have a greater density.
particle motion increases as temperature goes down.

Explanation:

• "The particles of a gas are at a higher temperature than its solid or liquid form. They have more kinetic energy. They have a lower density."
• In the kinetic - molecular theory, as temperature increases, particle motion (and thus kinetic energy) increases. Gases generally have higher temperatures (more thermal energy input) compared to their solid or liquid forms (except in some special cases like plasma - gas transitions, but in the common solid - liquid - gas triad).
• Density is mass per unit volume. Gas particles are more spread out (larger volume for the same mass) than solid or liquid particles, so they have lower density.
• "Particle motion increases as temperature goes up."
• This is a fundamental principle of the kinetic - molecular theory. Temperature is a measure of the average kinetic energy of particles. As temperature ($T$) increases, the average kinetic energy ($KE=\frac{3}{2}kT$, where $k$ is the Boltzmann constant) of particles increases, and so does their motion.
• "All forms of a pure substance are affected by changes in temperature. Only the gas form is affected by changes in volume and pressure."
• Solids and liquids are also affected by pressure (e.g., water under high pressure has different properties, and solids can be compressed to some extent). However, gases are highly compressible (Boyle's law: $P_1V_1 = P_2V_2$ at constant temperature) and their volume and pressure relationships are more pronounced and follow simple gas laws (Boyle's law, Charles's law, etc.) compared to solids and liquids.

Answer:

• "The particles of a gas are at a higher temperature than its solid or liquid form. They have more kinetic energy. They have a lower density."
• "Particle motion increases as temperature goes up."
• "All forms of a pure substance are affected by changes in temperature. Only the gas form is affected by changes in volume and pressure."