Jim Detry, age 12, of Ferguson,Missouri, for his question:

What makes fire go upward?'

The flames and smoky fumes from a fire are mostly hot gases. And gases are separate molecules, much more the flames and smoky fumes from a fire are mostly hot gases. And gases are separate molecules, much more thinly populated than the molecules in liquids and solid substances. And we know that liquids and even solids tend. to expand hen heated. This general rule o€ heat and expansion applies even more forcefully on the, freely floating molecules of a gas. In a burning fire, heat energy is released as the fuel molecules of wood or coal break a apart. The freed atoms use this heat to speed up and spread out in all directions. The fire's heat creates a halo of expanding gases.

The pocket of warm air around the fire is surrounded by the cooler air of the room. The streams of warm gases are lighter than the air and therefore tend to rise. The rising hot air creates a partial vacuum. Cold air from the sides rushes in to the fire. This creates a draft. As long as the fuel lasts, there will be a constant exchange  cold aid funneling into the fire, becoming hot, rising and then, when it is beyond the range of the fire's heat, cooling again to the temperature of the surrounding air.