Topic: Density
Q. Define density.
Ans. Density is mass per unit volume.
Mathematically ρ =
𝒎
𝒗
The SI unit of density is kg/m3.
Q. State the relationship between density,
mass and volume.
Ans. Density is directly proportional to mass
i.e. more mass, more density and vice versa.
Density is inversely proportional to volume
i.e. more volume, less density and vice versa.
Q. State which of the following is denser.
a) Two spherical objects having same mass
but one has volume of 2cm3 and other has
volume of 5cm3.
Ans. The sphere having volume of _________
b) Two boxes having same volume, one is
made of wood and other is made of steel.
Which is denser?
Ans. The box made up of ________
Note: for unit conversion
From Kg/m3 to g/cm3 divide by 1000
From g/cm3 to Kg/m3 multiply by 1000
Q. A metallic hammer has mass of 500g and
volume of 18cm3. What is its density?
Ans.
Q. A wooden box has volume of 500 cm3 and
mass of 2500 g. Calculate its density in
kg/m3.
Q. A beaker contains 50ml of water having a
mass of 50 grams. What is its density?
Q.1. A block of ice has density of 900 Kg/m3.
Its volume is 0.03m3 what is the mass of the
ice block?
M = pxv = 900x0.03 = 27Kg
Q.2. A rock has density of 14000 kg/m3. If
the mass of the rock is 600kg what is its
volume.
V = m/p = 600/14000 = 0.04285 = 0.043 m3
Q.3. Water has density of 1g/cm3. If the
volume of water is 0.5m3. What is its mass is
kg?
P = 1 x1000 = 1000 kg/m3
m= pxv = 1000x0.5 = 500 m3
Q.4. A small cube of iron has sides with
length 0.15 m. If the mass of the cube is 26.6
kg, what is its density? Give your answer to
the nearest kilogram per cubic meter.
V = lxlxl = 0.153 = 3.375x10-3
P = m/v = 26.6/3.375x10-3
P = 7880 kg/m3
Q.5. It is worked out that a solid gold crown
has a volume of 150 cm3.Find the mass of
the gold crown, using a value
of 19 300 kg/m3 for the density of gold. Give
your answer to one decimal place
Q.6. Find the volume of a 54 kg block of
aluminum. Use a value of 2,700 kg/m3 for
the density of aluminum.
V = m/p = 54/2700 = 0.02 m3
Q.7. A bowling ball has a mass of 5.5 kg. The
bowling ball is a sphere with a radius of 7
cm. What is the density of the bowling ball?
Give your answer to the nearest kilogram
per cubic meter.
r= 7/100 = 0.07m
V = 4/3x3.14x (0.07)3 = 0.0014 m3
P = m/v = 5.5/0.0014 = 3830 kg/m3
Q.8. A brick has a mass of 3.5 kg .It is a
rectangular prism with side lengths of 23 cm,
11 cm, and 7 cm. What is the density of the
brick? Give your answer to the
nearest kilogram per cubic meter.
Lengths = 23/100 = 0.23m
11cm = 11/100 = 0.11m
7cm = 7/100 = 0.07m
V = 0.23x0.11x0.07 = 0.00177 m3
P = m/v = 3.5/0.00177 = 1976 = 1980 kg/m3
Q. State the instruments used to measure
density of a regular shaped object.
Ans. Meter ruler and top-pan balance.
Q. Describe how to measure the density of
regular shaped object.
Ans. Place the object on top-pan balance and
record its mass.
Measure the dimension of object using ruler
and find its volume.
Calculate density of the object using
equation ρ = m/V.
Q. An object has density of 50g/cm3 and
mass of 2kg. Calculate its volume.
Q. A liquid has volume of 15cm3 and density
of 40g/cm3. Calculate it's mass.
Topic: Density of irregular shaped object.
Q. Describe how to calculate the density of
an irregular shaped object.
Ans. 1. Record the mass of the object using
top-pan balance.
2. Record the volume of the object using
liquid displacement method.
3. Calculate the density of the object using ρ
= m/v
Q. Describe how to measure the density of
liquid.
Ans. 1. Place the empty measuring cylinder
on the top-pan balance and record its mass
(m1)
2. Pour some liquid in the measuring
cylinder and record its volume and mass
(m2).
3. Calculate the mass of the liquid using
m = m2 – m 1
4. Calculate the density using equation
ρ=m/v