DENSITY
Definition: Density is the mass per unit volume.
𝑚𝑎𝑠𝑠
Density = 𝑣𝑜𝑙𝑢𝑚𝑒
Examples
1. Calculate the density of each of the following:
a) A stone of mass 300g and volume 100cm3.
D=
𝑚
𝑣
=
300𝑔
100𝑐𝑚3
= 3g/cm3
b) A block of mass 2kg and volume 4m3.
D=
𝑚
𝑣
=
2𝑘𝑔
4𝑚3
= 0.5kg/m3
2. The block shown below measures 10cm by 12cm by 3cm. The density of the
material from which the block was made is 2g/cm3. Calculate the mass of the
block.
D=
𝑚
𝑣
2g/cm3 =
𝑚
10𝑐𝑚 𝑥 12𝑐𝑚 𝑥 3𝑐𝑚
=
𝑚
360𝑐𝑚3
m = 2g/cm3 x 360cm3 = 720g
3. Water has a density of 1000kg/m3.
a) Calculate the volume of 500kg of water.
𝑚
D= 𝑣
1000kg/m3 =
500𝑘𝑔
𝑣
1000vkg/m3 = 500kg
V = 0.5m3
b) Calculate the mass of 3m3 of water.
𝑚
D= 𝑣
1000kg/m3 =
𝑚
3𝑚3
=
m = 1000kg/m3 x 3m3 = 3000kg
Experimental determination of density
Experiment 1
Aim: To determine the density of a solid with a regular shape.
i. Measure the mass of the solid using a beam balance.
ii. Measure the length (l), breadth (b) and height (h) using a ruler.
iii. Volume = l x b x h
iv. Density =
𝑀𝑎𝑠𝑠
𝑉𝑜𝑙𝑢𝑚𝑒
1 | Physics notes – P C Musonda – KCM Konkola Secondary Trust School
Experiment 2
Aim: To determine the density of a solid with an irregular shape.
i.
Measure the mass of the solid using a beam balance.
ii.
Pour water into a measuring cylinder.
iii.
Read and record the volume (V1)
iv.
Tie the solid to a string.
v.
Gently lower the solid into the water in the measuring cylinder.
vi.
Read and record the new volume (V2)
vii.
viii.
Volume = V2 – V1
Density =
𝑀𝑎𝑠𝑠
V2
V1
𝑉𝑜𝑙𝑢𝑚𝑒
Experiment 3
Aim: To determine the density of a solid with an irregular shape using eureka
(overflow or displacement) can.
i.
Measure the mass of the solid using a beam balance.
ii.
Pour water into the displacement can until it starts coming out of the
spout.
iii.
Wait for the water to stop coming out of the spout.
iv.
Place a measuring cylinder under the spout.
v.
Gently lower the solid into the water in eureka can.
vi.
Read and record the volume of the water collected.
vii.
Density =
𝑀𝑎𝑠𝑠
𝑉𝑜𝑙𝑢𝑚𝑒
Experiment 4
Aim: To determine the density of water.
i.
Measure the mass of an empty measuring cylinder (m1).
ii.
Pour the water into the cylinder. Read and record the volume.
iii.
Measure the mass of the cylinder with the water in it (m2).
iv.
Mass of water = m2 - m1
v.
Density =
𝑀𝑎𝑠𝑠
𝑉𝑜𝑙𝑢𝑚𝑒
Examples
1. A stone of mass 30g is immersed into water in a measuring cylinder. The water
level rises from 70cm3 to 90cm3.
a) Calculate the density of the stone.
D=
𝑚
𝑣
=
30𝑔
90𝑐𝑚3−70𝑐𝑚3
= 1.5g/cm3
b) What volume would 60g of the same stone occupy?
D=
𝑚
𝑣
2 | Physics notes – P C Musonda – KCM Konkola Secondary Trust School
1.5g/cm3 =
V=
60𝑔
1.5𝑔/𝑐𝑚3
60𝑔
𝑣
= 40cm3
c) What would be the mass of 1000cm3 of the stone?
𝑚
D= 𝑣
1.5g/cm3 =
𝑚
1000𝑐𝑚3
m = 1.5g/cm3 x 1000cm3 = 1500g
HOME WORK 1
1. Calculate the density of each of the following:
a) A stone of mass 200g and volume 50cm3.
b) A liquid of mass 120kg and volume 0.15m3.
2. The concrete slab measures 15m by 12m by 2m. The density of the material from
which the slab was made is 2.5kg/m3. Calculate the mass of the slab.
3. Water has a density of 1000kg/m3.
a) Calculate the volume of 300kg of water.
b) Calculate the mass of 25m3 of water.
4. A stone of mass 50g is immersed into water in a measuring cylinder. The water level
rises from 40cm3 to 60cm3.
a) Calculate the density of the stone.
b) What volume would 100g of the same stone occupy?
c) What would be the mass of 500cm3 of the stone?
5. Use the figure below to determine the density of the solid immersed in the liquid.
50cm3
20cm3
60g
150g
3 | Physics notes – P C Musonda – KCM Konkola Secondary Trust School