Answer:
We are asked to describe the half-life of the radioactive materials.
- Hence the 3rd option is correct
this is the answer of your question .
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Answer:
<em><u>spontaneous composition</u></em> is the ingnition
of the substance due to the repid oxidation of its on material.
There is no requirement of heat of external sources.
<em><u>Rapid composition</u></em> on the other hand release large amount of heat and light energy.
Explosion and the firecracker is the best example of Rapid composition.
Difference between Gas and Vapour:
Gas:
A thermodynamic state in which a substance exists only in one phase i.e. Gas phase. In above given examples N₂, He and CO₂ exists as gases at room temperature. These gases cannot form a solid or liquid phase along with gas phase as these states requires very low temperatures.
Vapours:
It is a thermodyanamic state in which a substance exists in more than one phase. In given options Sulfur can exist in vapor state. This is because sulfur exists in a cyclic or chain form due to catenation (self linkage property). Therefore, a lower members of S allotrops can form a vapours.
What are stars made of? Basically, stars are big exploding balls of gas, mostly hydrogen and helium. Our nearest star, the Sun, is so hot that the huge amount of hydrogen is undergoing a constant star-wide nuclear reaction, like in a hydrogen bomb.
In a spiral galaxy like the Milky Way, the stars, gas, and dust are organized into a "bulge," a "disk" containing "spiral arms," and a "halo." Elliptical galaxies have a "bulge-shape" and a "halo," but do not have a "disk.
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