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which laboratory activities involve chemical changes? check all that apply.

leaving a copper penny in vinegar until it turns green
boiling saltwater for several minutes until only solid salt remains
extracting iron filings from a sand mixture using a magnet
crushing a rock with a hammer to extract mineral deposits
putting an iron nail outside for a month and observing changes

The correct activities are leaving a copper penny in vinegar until it turns green, and putting an iron nail outside for a month and observing changes.

Explanation:

The formation of the green component on the copper penny and the formation of rust on the iron nail when kept outside for a month are the illustrations of chemical changes. On the other hand, extracting fillings or iron from a sand mixture with a magnet, boiling salt water away, and crushing rock with a hammer are the illustrations of physical modifications.

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explanation:

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.