Introduction to hydrometers and density
The density of sugar solutions depends on the amount of sugar dissolved. The sugar content of an unknown aqueous solution can be determined by comparison of its density with that of solutions containing known amounts of sugar.
The relative density of two solutions can be determined quickly using a hydrometer. A hydrometer is an instrument that can be used to measure the relative density of liquids. The hydrometer that is used in this experiment is an inverted plastic dropper weighted with sand.
The hydrometer sinks further into less dense liquids and floats higher in more dense liquids.
Why is this so?
The volume of liquid displaced by a floating object has the same mass as the floating object.
If the density of the liquid is higher, a smaller volume of liquid needs to be displaced to achieve the same mass of liquid AND more of the floating object is above the surface.
If the density of the liquid is higher, a smaller volume of liquid needs to be displaced to achieve the same mass of liquid AND more of the floating object is above the surface.