Page 91 - Physics

Density and relative density

Density of a liquid
(
The density of a liquid can also be Mass of liquid = 600 − 500)g = 100g.
calculated if its mass and volume are
known. Thus, the density of a liquid can be Density of liquid,
determined through the following steps:

1. Measure an empty beaker; record it ρ = Mass of liquid
as m . Volume of liquid
0
2. Using a burette, run out a known 100 g = 4 g cm 3
Density of liquid, =
volume ()V of the liquid into the 25 cm 3
beaker and measure the mass; record
it as m . Therefore, density of liquid Y
1 is 4 g/cm .
3
3. Subtract m from m to get the mass
0
1
of the liquid, that is,
(
mass of liquid = m − m ). Acti vity 4.5
1
0
4. Calculate the density of the liquid Aim: To determine the densities
by dividing mass obtained in step of kerosene and milk.
(3) by the known volume of liquid, Materials: Beakers, pipettes, beam
that is; balance, kerosene and
Mass of a liquid ( m - m ) g milk
Density of liquid = = 2 1 .
Volume of a liquid V cm 3
Procedure
( m - m ) g 1. Weigh a dry empty beaker using a
= 1 0 ⋅ weighing balance and record it as,
V cm 3
m .
0
2. Use a pipette to accurately measure
Example 4.5 20 ml of kerosene and transfer it into

In an experiment to determine the the weighed beaker.
density of liquid Y, a Form One student 3. Measure the mass of the beaker with
obtained the following results: Mass of kerosene and record it as m .
1
beaker = 500 g and Mass of beaker + 4. Repeat steps 1 to 3 for milk.
liquid (25 cm ) = 600 g. What did the Questions
3
student obtain as the density of liquid Y?
(a) Calculate the mass of the 20 ml
of kerosene and milk.
Solution
Volume of liquid Y = 25 cm 3 (b) Calculate the density of kerosene

Mass of empty beaker = 500 g and milk.
Mass of beaker + liquid Y = 600 g (c) Why is it necessary to measure
the mass of the empty beaker?

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Physics Form 1 Final.indd 85 16/10/2024 20:56