Questão 19 - CESGRANRIO 2012

Text II

Discover Magazine: Environment 10 Things You Didn’t Know About...Fire

by Lee Aundra Keany From the October 2011 issue; published online October 7, 2011

 

1 - Fire is an event, not a thing. Heating wood

or other fuel, releases volatile vapors that can

rapidly combust with oxygen in the air; the resulting

incandescent bloom of gas further heats the fuel,

releasing more vapors and perpetuating the cycle.

2 - Most of the fuels we use derive their energy

from trapped solar rays. In photosynthesis, sunlight

and heat yield chemical energy (in the form of wood

or fossil fuel). Contrastingly, fire uses chemical energy

to produce light and heat.

3 - Assuming stable fuel, heat, and oxygen

levels, a default house fire will double in size at every

minute.

4 - Earth is the only known planet where fire can

burn. Everywhere else: scarce oxygen.

5 - Spontaneous combustion is real. Some fuel

sources can generate their own heat—by rotting, for

instance. Pistachios have so much natural oil and are

so prone to heat-generating fat decomposition that

the International Maritime Dangerous Goods Code

regards them as dangerous.

6 - Oxygen supply influences the color of

the flame. A low-oxygen fire is made up of lots of

uncombusted fuel particles and will give off a yellow

glow. A high-oxygen fire sets off a blue flame. So

candle flames are blue at the bottom because that’s

where they take up fresh air, and yellow at the top

because the rising fumes from below cut down on the

oxygen supply from the upper part of the flame.

7 - Fire can make water. Place a cold spoon

over a candle and you will observe the water vapor

condense on the metal. This is because like most

organic materials, including wood and gasoline,

candle wax contains hydrogen, which bonds with

oxygen and amounts to H2O when it burns.

8 - We’ve been at this a long time: Charred

bones and wood ash indicate that early hominids were

tending the first intentional fires more than 400,000

years ago.

9 - Nature’s been at it awhile, too. A coal seam

about 140 miles north of Sydney, Australia, has been

burning by some estimates for 500,000 years.

10 - A good burn in history: The 1666 Great Fire

of London destroyed 80 percent of the city but also

ended an outbreak of bubonic plague that had killed

more than 65,000 people the previous year. The fire

fried the rats and fleas that carried Yersinia pestis, the

plague-causing bacterium.

Available at <http://ad.doubleclick.net/jump/site125. tmus/environment;tile=2;sz=123x32;ord=123456789?” target=”_blank”> Retrieved on: Dec. 02, 2011. Adapted.

In Text II, the word in parentheses describes the idea expressed by the expressions in