Why is fire hot?

[mbinnc]

hello, i am a homeschool mom with three inquisitive children. they would love to know why fire is hot...if anyone can answer this question i would appreciate it. i realize that this may be difficult to put in laymans terms, but any information would be helpful... thanks :) ~mbinnc

 

[Integral]

Fire is the result of a chemical reaction (oxidation) which releases energy stored in chemical bonds. This released energy is the "heat" you feel.

As the chemical reaction releases stored energy, volatile chemicals are released, it is these hot vapors which you see and call flames. The color of the flame is an indication of the chemicals being released, thus you will see different colors in different types of wood.

 

[Gonzolo]

Adding to what Integral just said, in a common fire, the energy is released in two radiative forms, light (colors), and infrared. Light radiation is detected by our eye, and infrared radiation is detected by our skin. It is the capture of infrared radiation by nerve endings in our skin that causes us to feel heat. The nerve endings can simply be called heat receptors (there are other types of nerve endings). The nerves, like a phone wire, tell our brain ("us") not to get too close.

 

[Adrian Baker]

The color of the flame is an indication of the chemicals being released, thus you will see different colors in different types of wood.

The common yellow colour seen in flames is from carbon atoms. When a flame gets sufficient Oxygen, all the Carbon gets converted to Carbon Dioxide, so there is no Yellow colour... or soot!


Oh, and welcome to the forum by the way..

 

[rcgldr]

Actually the heat alone is enough to produce colors, depending on the material. The energy in chemical reactions is due to a change in the energy of the electrons, which can have different levels of energy, depending on the atoms / molecules invovled. In the case of fire, the combining of oxygen atoms with other atoms (or molecules) results in the electrons releasing energy and ending up in a lower energy state. This release of energy is generally in the form of heat (infrared light waves). If there's enough heat generated, it also creates higher frequency waves that can be seen.

With an electric oven, you can still get heat and light without any fire, just the increase in energy of the molecules generates the heat, and the temperature determines the color viewed.

If you've ever had a chemical cold pack, this is a chemical reaction that consumes heat. After breaking the back and letting the chemicals combine, the pack gets cold because the chemical reaction results in absortion of energy, with the electrons going into a higher engergy state.