Section 5 Density and pressure


Notes
Step 1

List all the information in symbol form and change into appropriate and consistent SI units if required.

l=10.0cm

w=2.0cm

h=5.0cm

m=80g

ρ=?

Step 2

Use the correct equations.

V = l × w × h and
ρ =
 m 

 V 

Step 3

Calculate the answer by putting the numbers into the equations.

ρ =
 m 

 V 
=
 80 

 100 
  = 0.80g/cm3 (2 sig. figs)

ALWAYS REMEMBER TO STATE THE UNIT FOR CALCULATED QUANTITIES.

The unit g/cm3 is acceptable for density, although the SI unit is kg/m3. This is why cm has not been converted into m in the above calculation.

Determining the density of a liquid

  • A measuring cylinder is used to measure the volume of a liquid. Volume must be measured to the bottom of the meniscus (the bottom of the curved surface of the liquid).
    correct alignment
  • When using a measuring cylinder, be careful to avoid parallax error (see pages 2-3). If the volume is not measured at right angles to the meniscus, parallax error will cause incorrect high or low measurements.
 
Return to topics
 
Unsure which syllabus you are studying? Click here