Pure Substances cannot be separated easily or, sometimes at all.
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Answer:
A directory of relatives' phone numbers
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Explanation:
<em>Transparent because you can see right through it </em>
Answer:
If the volume of a gas increased from 2 to 6 L while the temperature was held constant, <u><em>the pressure of the gas decreased by a factor of 3.</em></u>
Explanation:
Boyle's law that says "The volume occupied by a given gaseous mass at constant temperature is inversely proportional to pressure." This means that if the pressure increases, the volume decreases, while if the pressure decreases, the volume increases.
Boyle's law is expressed mathematically as:
Pressure * Volume = constant
or
P * V = k
To obtain the proportionality factor k you must make the quotient:

k= 3
This means that <u><em>if the volume of a gas increased from 2 to 6 L while the temperature was held constant, the pressure of the gas decreased by a factor of 3.</em></u>
<h2>Answer : Option B) Ozone</h2><h3>Explanation :</h3>
The layer of atmosphere which contains a substance(Ozone) that was created from a product of living thins (oxygen) and protects living things (from harmful UV rays).
Oxygen in the atmosphere reacts in presence of UV rays and forms Ozone.
This ozone forms a protective layer around the earth and protects it from harmful UV rays.