Final answer:
A hydrometer is an instrument used to measure the specific density of liquids. When measuring the density of a solution of water and soil particles, the hydrometer is gently lowered into the liquid until it floats freely, and the point of contact with the liquid's surface indicates the relative density. The measurement time can range from seconds to minutes.
Step-by-step explanation:
A hydrometer is an instrument used to measure the specific density of liquids by utilizing the concept of buoyancy. It consists of a sealed glass tube with a wider bottom for buoyancy and a narrow stem with graduations for measurement. When the hydrometer is gently lowered into a solution of water and soil particles, it floats freely, and the point where the liquid touches the stem indicates the relative density.
The time it takes for the hydrometer to measure the density of the solution can vary depending on the specific circumstances. In general, it may take seconds to minutes for the hydrometer to provide an accurate measurement. However, other factors such as the nature and concentration of soil particles can affect the measurement time as well.