Term: 1^{st} Term
Week: 7
Class: Senior Secondary School 1
Age: 15 years
Duration: 40 minutes of 5 periods each
Date:
Subject: Physics
Topic: Density and relative density
SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to
INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source
INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures
INSTRUCTIONAL PROCEDURES
PERIOD 12
PRESENTATION 
TEACHER’S ACTIVITY 
STUDENT’S ACTIVITY 
STEP 1 INTRODUCTION 
The teacher reviews the previous lesson on scalar and vector quantity 
Students pay attention 
STEP 2 EXPLANATION 
He defines density and describes how to determine it

Students pay attention and participates 
STEP 3 DEMONSTRATION 
He defines relative density and describes how to determine it for solids and liquids

Students pay attention and participate 
STEP 4 NOTE TAKING 
The teacher writes a summarized note on the board 
The students copy the note in their books 
NOTE
DENSITY AND RELATIVE DENSITY
The density of a substance is the mass per unit volume of the substance. Density = mass of a given substance
Volume of the substance
Density is scalar quantity& measured in kgm^{3} (kilogram per cubic meter)
DETERMINATION OF DENSITY
The determination of density involves the determination of a mass and a volume. The mass can be found by weighing. The density of a substance can be determined using a graduated density bottle.
Relative Density
Relative density is also known as specific gravity. Relative density of a substance is defined as the density of the substance per density of water.
R.D = Density of the substance
Density of water
R.D is also equal to the ratio weight of a substance to weight of an equal volume of water. As weight is proportional to mass
R.D = mass of substance
Mass of equal volume of water
DETERMINATION OF R.D OF SOLID (E.G. SAND)
Mass of empty bottle = m1
Mass of bottle + sand = m2
Mass of bottle + sand + water = m3
Mass of bottle + water only= m4
Mass of sand = m2 – m1
Mass of water added to sand = m3 –m2
Mass of water filling the bottle = m4 – m1
Mass of water having the same volume as sand = (M4M1) – (M3M2)
Relative density = Mass of sand
Mass of equal volume of water
R.D = m2 – m1
(m4  m1)  (m3 m2)
DETERMINATION OF R.D OF LIQUID
Mass of empty density bottle = m1
Mass of bottle filled with water = m2
Mass of bottle filled with liquid = m3
R.D of liquid = m3 – m1
m2 – m1
Examples
A glass block of length 10cm width 8cm and thickness 2cm has a mass of 400g. Calculate the density of the glass.
Solution
l = 10cm = 0.1m, b = 8cm = 0.08cm, h = 2cm = 0.02m, m = 400g = 0.4kg
V = l x b x h = 0.1 x 0.08 x 0.02
= 0.00016m^{3}
Density = Mass (m) = 0.4= 2500kgm^{3}
Volume (V) 0.00016
Examples
Calculate the volume in m^{3} of a piece of wood of mass 500g and density 0.76gcm^{3} Mass of the wood = 500g
Solution
Density = 0.76gcm^{3}
Volume =?
Volume = mass / density
0.76
Volume = 658cm^{3} = 6.58 x 104 m^{3}
^{ }
Example 2
An empty relative density bottle has a mass of 15.0g. When completely filled with water, its mass is 39.0g. What will be its mass if completely filled with acid of relative density 1.20?
Solution
m1, mass of empty bottle = 15.0g
m2, mass of bottle + water = 39.0g
Mass of acid = n – 15.0g
Mass of water = 39.0 – 15.0g
= 24.0g
R.D = 1.20
R.D = n – 15.0g
39.0 – 15.0g
1.20 = n –15.0
24.0
n 15.0= 1.20x24.0
n 15= 28.8
n =28.8+15
n=43.8g
NOTE: The hydrometer is an instrument used to measure the relative density of liquids
EVALUATION: 1. Define density
CLASSWORK: As in evaluation
CONCLUSION: The teacher commends the students positively