Answer:
an indicator helps us to see the equivalence point (or end point of the valuation) during a titration experiments by causing the color change.
Explanation:
A closed system is a system that makes no physical or chemical exchanges with its environment. Of these systems provided as choices (tree, human, clock, car), only a clock does not make exchanges with the environment, except for energy.
Therefore, of that list, only a clock would be a closed system.
Hope that helped! =)
The number of oxygen atoms in a molecule
A life expectancy of 2 to 5 years less than peers.
