Astronauts<span> must </span>wear<span> spacesuits whenever they leave a spacecraft and are exposed to the environment of </span>space<span>. In </span>space, there is no air to breath and no air pressure.Space<span> is extremely cold and filled with dangerous radiation. Without protection, an</span>astronaut<span> would quickly die in </span>space<span>.</span>
Oxygen<span> is a </span>chemical element<span> having a symbol </span>O<span> and having an </span>atomic number<span> 8.
Oxygen is a pure substance , and it is not a mixture or solution, Niether it is a compound ... Instead , it forms chemical compounds by reacting with other elements.
So , according to above explanation ,
A. A pure substance , is the correct answer.</span>
Answer: The correct answer is: " endothermic . "
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<u>Note</u>: Heat flows <u> into </u> [heat <u> may be </u> absorbed within] an "<u>endothermic</u>" reaction or system
To the contrary, heat flows <u> </u><u>out </u> [heat <u> may </u><em> </em>exit from or <u> may be </u> released from] an "<u>exothermic</u>" reaction or process.
<u>Hint</u>: Think of the "prefixes" of: "<u>endo</u>thermic" and "<u>exo</u>thermic" :
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1) endo- = "within" (as in "endothermic" —heat tends to be absorbed/"within"/"released within"/released within"/into" ;
2) exo- = " outwards"/"exit" (as in "exothermic") —heat tends to '"exit"/leave/escape from/"be released out of/form".
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Hope this is helpful to you!
Best wishes to you in your academic pursuits
—and within the "Brainly" community"!
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Answer:
put a test tube over the opening, remove it and quickly put a lit splint near the mout or in the tube. if you hear a squeaky pop it is hydrogen.
Explanation:
hydrogen ignites in air.
