Question

describe changes in temperature and density; convection cell

Explanation:

To describe the changes in temperature and density in a convection cell (like around a fire):

1. Near the heat source (fire): Air is heated. Temperature increases, so density decreases (since warmer air expands, $

ho=\frac{m}{V}$, and $V$ increases for fixed $m$). This low - density air rises.

1. As air rises: It moves away from the heat source, cools down (temperature decreases). As it cools, it contracts, so volume decreases and density increases (using the same density formula, $V$ decreases for fixed $m$).
2. As dense air sinks: It moves back toward the heat source. Near the heat source, the cycle repeats as the sinking air is reheated.

For the convection cell diagram (starting from the bottom - left box near the fire, moving clockwise):

• Bottom - left box (near fire): “Temperature increases, density decreases (air heats up, rises)”
• Middle box (rising air): “Temperature decreases (cools), density increases (air cools, starts to sink)”
• Top box: “Temperature low, density high (cooled air at the top, ready to sink)”
• Bottom - right box (sinking air): “Temperature increases (reheats near fire), density decreases (cycle repeats)”

Answer:

• Bottom - left (near fire): Temperature increases, density decreases.
• Middle (rising): Temperature decreases, density increases.
• Top: Temperature low, density high.
• Bottom - right (sinking): Temperature increases, density decreases.