Final answer:
The feeling of cool air when blowing through a narrow mouth opening demonstrates the relationship that as volume increases, the temperature decreases, which aligns with Charles's Law.
Step-by-step explanation:
When you make a narrow opening with your mouth and blow air out, it feels cool because of the relationship between the volume and temperature of a gas. This can be explained by the combined gas laws, specifically Boyle's Law and Charles's Law. Boyle's Law indicates that when the volume decreases, the pressure increases if the temperature is constant. However, in this case of blowing air, we are not only decreasing the volume by the narrow opening of our mouths, but also allowing the air to expand and thereby cool when it exits.
Therefore, the correct answer here would be (c) Volume increases and temperature decreases. This is because the air exiting your mouth expands into the larger atmosphere, causing a pressure drop and an associated temperature decrease. This behavior is consistent with Charles's Law, which states that gas volume increases as temperature increases, but conversely, when a gas expands (volume increases) without adding heat, its temperature decreases.
\