Lesson Notes By Weeks and Term - Senior Secondary 1

Fluids at rest and in motion

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Term: 3rd Term

Week: 4

Class: Senior Secondary School 1

Age: 15 years

Duration: 40 minutes of 5 periods each

Date:       

Subject:      Physics

Topic:-       Fluids at rest and in motion

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

  1. Define surface tension, capillarity, adhesion and cohesion
  2. State the applications of surface tension

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

PRESENTATION

TEACHER’S ACTIVITY

STUDENT’S ACTIVITY

STEP 1

INTRODUCTION

The teacher reviews the previous lesson on the crystalline substances

Students pay attention

STEP 2

EXPLANATION

He defines and explains surface tension, capillarity, adhesion and cohesion

 

 

Students pay attention and participates

STEP 3

DEMONSTRATION

He states and explains the applications of surface tension

 

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

FLUIDS AT REST AND IN MOTION

The molecules of gases are more free to move than those of solids. Therefore, both liquids and gases are able to flow. For this reason, they are grouped together as fluids.

SURFACE TENSION

This is the force of attraction between the molecules of the liquids, which make the liquid to act like an elastic skin. It can also be define as the force per unit length acting on the liquid surface at right angle to one side of an imaginary line drawn on the liquid surface. Some effects of surface tension forces are: drops of water dripping slowly from tap water has a spherical shape, Mercury forms spherical pellet when poured on a table, Greased needle floats when gently dropped on water etc.

Surface tension can be reduced by (i) Adding of soap or detergents (ii) Heating (iii) Contamination etc.

Surface tension can be expressed mathematically as:

r =    𝐹

        2𝐿

r= Surface tension

F= Force

L= Length

Its S.I. Unit is Nm-1

APPLICATION OF SURFACE TENSION

  1. Waterproof Material e.g. Umbrella, Raincoat etc.
  1. Cleansing action of soaps and detergents. 

CAPILARITY: Capillarity or capillary action is the tendency of liquid to rise and fall in a narrow capillary tube when the tube is dipped into a liquid that wet it. The rising of the liquid depends on the following factors:

  1. Cross-sectional area of the tube.
  2. Surface tension.

COHESION: Is the force of attraction between molecules of the same kind. For example, the cohesion between mercury molecules makes mercury stick together when poured into a glass without wetting it.

ADHESION: This is the force of attraction between molecules of different substances. For example, the adhesion between water molecule and glass makes water to wet glass

 

EVALUATION:   1. Define

  1. surface tension
  2. capillarity
  3. cohesion
  4. adhesion

      2. State the applications of surface tension

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively