A student measures the volume of a liquid using a measuring cylinder. What else needs to be measured by the…

Analyze the question The student already has the volume of the liquid. The question asks what other quantity is needed to find its density.

Concept Density is mass per unit volume:

Density (ρ) = Mass (m) / Volume (V)

Its SI unit is kg/m³ (or g/cm³ in the lab).

Solution

• Volume is already known from the measuring cylinder.
• To use ρ = m/V, the only missing quantity is the mass of the liquid.

Checking each option:

• A. Depth of the liquid: Not needed. The volume is already read from the graduations on the cylinder.
• B. Mass of the cylinder: On its own this is not enough. You would need the mass of the cylinder plus the liquid, and then subtract. The mass of the cylinder alone does not give the mass of the liquid.
• C. Mass of the liquid: This is the missing quantity in ρ = m/V, so it is what you need.
• D. Temperature of the liquid: Temperature affects density slightly, but it is not needed to calculate it.

In practice, you weigh the empty cylinder, then weigh it with the liquid in it. The difference is the mass of the liquid. Then:

ρ = (mass of liquid) / (volume of liquid)

Exam tip For any "how do you find density?" question, remember mass and volume. If volume is given, look for mass, and if mass is given, look for volume. Watch for trap options like "mass of the container", which are only part of the procedure.