<span>Acetic acid is under the family
of carboxylic acids which has a carboxyl group –COOH bond attached to the alkyl
group. Alkyl group can be methyl (CH3-), ethyl (CH3CH2-) and so on. The term
acetic also means methyl. So combining the two gives CH3COOH or HCH3CO2. The H
before the C in <u>H</u>CH3CO2 means that it is the H attached to the O in the carboxyl
group –COOH. You cannot write it as C2H4O2 because it would represent a
different compound.</span>
A. The bubbles are lighter than air.
B. There is matter that cannot be seen inside the bubbles.
C. The bubbles will burst before long.
D. The bubbles cannot be broken into smaller pieces.
Answer:

Explanation:
A radioactive isotope is an isotope that undergoes nuclear decay, breaking apart into a smaller nucleus and emitting radiation during the process.
The half-life of an isotope is the amount of time it takes for a certain quantity of a radioactive isotope to halve.
For a radioactive isotope, the amount of substance left after a certain time t is:
(1)
where
is the mass of the substance at time t = 0
m(t) is the mass of the substance at time t
is the half-life of the isotope
In this problem, the isotope is uranium-235, which has a half-life of

We also know that the amount of uranium left in the rock sample is 6.25% of its original value, this means that

Substituting into (1) and solving for t, we can find how much time has passed:

Answer:
Density is the correct answer choice.