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Asked by jossy to Christine, Edd, Jess, Nicolas, Zara on 17 Jun 2011.
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Jessica Chu answered on 17 Jun 2011:
i guess the best answer would be gas! There is gas all around us, including something that is burning. When things burn and you can see fire, this is a reaction with the thing that is burning and the oxygen in the air. The reaction changes the stored up energy from the thing that is burning into heat and light. If there is no fresh supply of oxygen around something that is burning the reaction stops, and the fire goes out.
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Edward Codling answered on 17 Jun 2011:
Fire is also energy of course – light and heat!
When chemicals react and change structure they either give off or take in energy from the environment around them.
There are some spectacular examples of this in a video here: http://video.google.com/videoplay?docid=-2134266654801392897#
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Zara Gladman answered on 17 Jun 2011:
I guess fire itself isn’t solid, liquid or gas but it can produce gas (like Jess said) and it burns liquids and solids.
Also, like Edd explained… fire is energy! Chemical reactions that give off a lot of energy may produce fire. Look at the fire produced when caesium (a very reactive metal!) is added to water… watch the whole video, then it’s the last one 🙂 pretty fun!: http://www.youtube.com/watch?v=uixxJtJPVXk Chemical reactions that give out energy are called ‘exothermic’. Reactions that take IN energy are called ‘endothermic’.
Looks like Derek from the Chromium zone has given a better explanation than an ecologist could give (check out the comments!).
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Christine Switzer answered on 17 Jun 2011:
Flaming fire is the oxygen-driven destruction of a fuel. The fuel can be solid, liquid or gas but the flames can only form in the gas phase. The burning of a solid or a liquid has multiple stages. The solid or liquid fuel has to be converted into a gas in order to have a flame. Once the flames have started, the flames can make enough heat to convert the fuel to a gas to burn.
In the movies, you might see flames following a pool of spilled petrol or some other liquid. Chemicals like petrol burn very well. Some of the liquid turns into a gas at normal temperatures so the fire can ignite very quickly. The hotter the fire gets, the faster the the fuel can turn into a gas. When the pool gets small enough, the fuel cannot turn into gas fast enough and the fire stops itself. There is residue leftover, which is why the forensic scientists can figure out what caused the fire.
Solids burn in a similar way except there are a few more steps in converting the fuel to gas. Often these fires are less efficient, which is why burnt solids can smell really bad and have more stuff left over than flaming fires.
Comments
Derek commented on :
Fire is usually a GAS. Sometimes it can have solid or plasma too (which I’ll explain below). In many cases the fuel is being vaporised by the heat. The burning then occurs as a gas. For example, gaseous ethanol, burning into gaseous water and carbon dioxide.
C2H5OH + 3 O2 → 2 CO2 + 3 H2O
The water in the flame is a gas, but it can condense later. If you put something very cold (like a beaker of ice water) over a ethanol or gas flame — but only for a second — you will see water droplets form. This is the gaseous water condensing into liquid on the cold surface. However, if you leave the beaker there, it will disappear again as the flame’s heat evaporates it.
However, there can also be solids in flames.
For instance, if you have a really smoky flame from a spilt-oil fire, then the flame is dark orange… even red and there is lots of smoke. The orange red is actually from SOLID particles of carbon (soot), which are heated so hot that they glow. As they cool, they go from orange to red to black.
It is also possible to have PLASMA in fire. Plasma is the fourth state of matter. Hotter than gas, it is where the nuclei and electrons split apart. It can also be thought of as ionised gas. Some fires are hot enough to produce this too.
As the others have explained, the light and heat are forms of energy.
(Greetings from the ChromiumZone!)