In a lava lamp, the upward movement of the clump is caused by a change in which property?

In a lava lamp, the upward movement of the clump is caused by a change in which property?

• A. its density
• B. its color
• C. its optical clarity
• D. its electrical conductivity

Answer: (A)

Buoyancy drives the movement. As the wax in the lava lamp is heated, it expands, so its density drops. When the clump becomes less dense than the surrounding liquid, the buoyant force pushing upward exceeds its weight, causing it to rise. When it cools, the wax contracts and its density increases, making it denser than the liquid, so it sinks. This cycle repeats, producing the rising-and-sinking blobs. Color, optical clarity, or electrical conductivity don’t affect buoyancy, so they don’t control the movement of the clump.

Buoyancy drives the movement. As the wax in the lava lamp is heated, it expands, so its density drops. When the clump becomes less dense than the surrounding liquid, the buoyant force pushing upward exceeds its weight, causing it to rise. When it cools, the wax contracts and its density increases, making it denser than the liquid, so it sinks. This cycle repeats, producing the rising-and-sinking blobs.

Color, optical clarity, or electrical conductivity don’t affect buoyancy, so they don’t control the movement of the clump.