Question

1.5 engage: states of matter
10 total points
answer the question correctly to continue:
what happens to a gas when it is heated?
its particles stick together and form a liquid
its particles shrink and become dense
its particles move faster and spread out
its particles freeze and stop moving

Explanation:

When a gas is heated, according to the kinetic - molecular theory of gases, the average kinetic energy of its particles increases. Kinetic energy is related to the speed of the particles ($KE=\frac{1}{2}mv^{2}$, where $m$ is the mass of the particle and $v$ is its speed). As the temperature (a measure of the average kinetic energy of particles in a substance) rises, the particles move faster. Also, in a gas, the particles are already in a state of random motion. With increased speed, they spread out more, especially if the volume is allowed to change (for example, in an open - ended container).

• The option “Its particles stick together and form a liquid” is incorrect. For a gas to turn into a liquid (condensation), it usually needs to be cooled (releasing energy) so that the intermolecular forces can pull the particles closer together.
• The option “Its particles shrink and become dense” is wrong. The size of gas particles (atoms or molecules) does not change with heating in the context of the states of matter we are considering here. The density of a gas can change with heating if the volume changes (e.g., through expansion), but the particles themselves do not “shrink.”
• The option “Its particles freeze and stop moving” is incorrect. Freezing is a process related to a liquid turning into a solid, which occurs when a substance is cooled, not heated. Gas particles are in constant motion, and heating increases their motion, not stops it.

Answer:

Its particles move faster and spread out.