What is a flammable chemical compound contained within a hollow tube that emits light, heat, and vapor when ignited?

A flare is a type of flammable chemical compound contained within a hollow tube, designed specifically to emit light, heat, and vapor when ignited. Flares are often used for signaling or illumination purposes, especially in emergency situations. When the flare is ignited, the chemical reaction within the tube produces a bright light, along with significant heat and gases, demonstrating the characteristics outlined in the question.

In contrast, fireworks are designed primarily for entertainment and typically have a more elaborate composition, including various chemical mixtures that create visual effects and sounds. While they also emit light and heat, their primary function is different from that of a flare.

Smoke bombs generate smoke rather than light and heat, which distinguishes them from flares. They usually consist of a different mixture of chemicals aimed at producing a dense smoke for signaling or obscuring vision.

An incendiary device is a broader term that refers to any weapon designed to set fire to objects or structures, often used in military contexts. While it may share some characteristics with flares, its purpose and the manner of deployment differentiate it significantly.

Thus, the flare is the best answer as it specifically fits the description of emitting light, heat, and vapor when ignited within a hollow tube structure.