PHYSICS Density Mr Rishi Gopie Mr R Gopie PHYSICS Density and Relative Density The density of a substance or material is defined as its mass per unit volume i.e. Density ρ = mass (m)/ volume (v)
Consider consistent (i.e. corresponding units) or the quantities involved.
QUANTITY Mass, m Volume, V Density UNITS g kg cm³ m³ gcm-­‐³ kgm-­‐³ The relative density of a substance or material is given by the following ratios: Relative density = density of substance or material/density of water (in same units) And Relative density = mass of certain volume of substance (or material) / mass of an equal volume of water Note that for any substance/material -
Density in kgm-³ = 1000 x density in gcm ³, and
Density in gcm-³ = density in kgcm-³/1000
Since the density of water is 1gcm-³ or 1000kgm-³ then the relative density of a
substance/material is numerically equal to its density expressed in gcm-³ (and therefore
numerically equal to its density expressed in kgm-³ divided by 1000).
Page 2 of 12 Mr R Gopie PHYSICS Consider Examples.
Material or Substance Density/ gcm-­‐3 Density/kgm-­‐3 Relative Density Gold 19.3 19300 19.3 Mercury 13.6 13600 13.6 Copper 8.9 8900 8.9 Aluminium 2.7 2700 2.7 Glass 2.5 2500 2.5 Water 1.0 1000 1.0 Ice 0.90 900 0.90 polythene 0.90 900 0.90 Wood (teak) 0.80 800 0.80 Paraffin(kerosene) 0.80 800 0.80 Petrol(gasoline) 0.80 800 0.80 Air 0.0013 1.3 0.0013 Hydrogen 0.00009 0.09 0.00009 Methylated Spirits 0.80 800 0.80 Page 3 of 12 Mr R Gopie PHYSICS 1) A rectangular block of material of relative density 2.0 has the following dimensions : 10cm x 80cm x 2.0cm a) Calculate the volume in : i)
cm3 ii)
mm3 iii)
m3 b) the density of the material of the block in i)
gcm-­‐3 ii)
kgm-­‐3 c) the mass of the block in i)
g ii)
kg d) the weight of the block 2) An empty measuring cylinder has a mass of 84g. A liquid is poured into the cylinder to a level of 19cm3. The mass of the cylinder and liquid is then 99g. A stone is submerged in the liquid rises to 55cm3 and the total mass of cylinder , liquid and stone becomes 154g. i)
Calculate the mass of the liquid in g ii)
Calculate the mass of the liquid in kg iii)
State the volume of the liquid in cm3 iv)
Calculate the volume of the liquid in mm3 v)
Calculate the volume of the liquid in m3 vi)
Calculate the density of the liquid in gcm-­‐3 vii)
State the volume of the liquid in kgm-­‐3 viii)
State the relative density of the liquid ix)
Calculate the mass of the stone in g x)
Calculate the mass of the stone in kg xi)
Calculate the volume of the stone in cm3 xii)
Calculate the volume of the stone in mm3 xiii)
Calculate the volume of the stone in m3 xiv)
Calculate the density of the stone in gcm-­‐3 xv)
Calculate the density of the stone in kgm-­‐3 xvi)
State the relative density of the stone xvii) Calculate the weight of the liquid xviii) Calculate the weight of the stone. Page 4 of 12 Mr R Gopie PHYSICS TUTORIAL Page 5 of 12 Mr R Gopie PHYSICS June 2002 paper 2 # 2
Page 6 of 12 Mr R Gopie PHYSICS Page 7 of 12 Mr R Gopie PHYSICS June 1995 paper 2 #1
Page 8 of 12 Mr R Gopie PHYSICS Page 9 of 12 Mr R Gopie PHYSICS Page 10 of 12 Mr R Gopie PHYSICS Jan 1999 paper 2 Page 11 of 12 Mr R Gopie PHYSICS Page 12 of 12