Question

Help please!!

If you rinse a 10mL graduated cylinder with water and then use it while it is still wet to measure out 10.0 mL sucrose solution, will the density you measure be greater or smaller than the true density of the solution? Why?

Answer 1

It indeed changes but i think this change is kind of insignificant, because remember that every instrument you use to measure has a margin of error and think this error is big enough to include a mistake of including a few drops of water.

Anyhow, not considering the margin of error, and assuming a perfect measure
If the cylinder is still wet, if exagerate we could say there's still 1 mL of water inside it.
To fill the full cylinder we add 9 mL of sucrose to the 1 ml of water, so in fact we're deluting the solution even more.

Density is the relation between mass and volume
\[D=\frac{ m }{ v }\] Now we know that volume will be constant when you add sucrose to a wet and non-wet cylinder, in both case volume will remain 10ml. Hence is the mass which will make a different. We ask ourselves: Which case has more mass? 10 ml of sucrose or 9 ml of sucrose + 1 ml of water, sucrose has more weight than water

So the density of the solution in the wet cylinder would be smaller than the true density of the solution.