Lesson Notes By Weeks and Term - Senior Secondary 1

Water

Get it on Google Play
Get it on the Apple App Store
  1. Home
  2. Lesson Notes By Weeks and Term
  3. Senior Secondary 1
  4. Water

Term: 3rd Term

Week: 1

Class: Senior Secondary School 1

Age: 15 years

Duration: 40 minutes of 5 periods each

Date:       

Subject:      Chemistry

Topic:-       Water

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

  1. Define water
  2. List the sources and uses of water
  3. Discuss the types of water and water pollutants
  4. Outline the steps in the laboratory preparation of water

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 deliquescent, hygroscopic and efflorescent substances

Students pay attention

STEP 2

EXPLANATION

He defines water and lists the sources and uses of water.

 

Students pay attention and participates

STEP 3

DEMONSTRATION

He discusses the types of water and water pollutants. He further outlines the steps in the laboratory preparation of water

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

WATER

Earth surface is covered with 70% water. Of these about 96% is sea water, 3% is in the form of ice while the remaining 1% is fresh water.

 

The 1% is not really enough for lives on land. Other waters contain among other things dissolved salts, bacteria, organic matters, as well as other pollutants. Hence the need to treat the available water for usage.

 

Physical Properties of water

  1. Water is a colourless, odourless and tasteless liquid.
  1. The only substance that exists in the three states of matter
  2. Freezes at 0oC
  3. Boils at 100oC at 760mmHg or 1 atmospheric pressure Maximum density of 4gcm-3 at 4oC

Chemical properties of water

  1. Water is a universal solvent. that is, it is capable of dissolving more substance than any other solvent. Pure water has a pH of 7
  2. Water react with active metals (K, Na, Ca) to form metallic hydroxides and Hydrogen gas

Na(s) + H2O(l)    NaOH(aq) +H2(g)

 

Note the state of matter for the water to use depends on the position of the elements on the electrochemical series

 

SOFT AND HARD WATER

Soft water is water that contains little or no dissolved mineral salts in them.

 

Water is a universal solvent and is capable of picking impurity easily.

Water is said to be hard when it contains high concentration of mineral salts especially of calcium and Magnesium.

Hard water does not lather readily with soap

Hardness in water is divided into temporary and permanent hardness

Temporary hardness is caused by the presence of Ca(HCO3)2 or Mg(HCO3)2 as dissolved minerals .

Temporary hardness can be removed by mere boiling. Hence it is called temporary hardness. As in the equation below

 

Ca(HCO3)2 (aq)

CaCO3(s) + H2O(l)

 

Permanent hardness is caused by the presence of dissolved calcium and magnesium salts of tetaoxosulphate VI and Chlorides. It cannot be removed by ordinary boiling

 

Methods of Removing hardness from Water

Using Ion Exchange Resin : the hard water is allowed to pass through a chamber containing ionized Na+ compounds where the ca2+ and Mg2+ in the hard water are replaced by Na+ until all are exhausted.

Ca2+ + sodium form of  2Na+  + calcium form of

Ion exchange resin Ion exchange resin The use of sodiumtrioxocarbonate IV (washing soda). This precipitate the calcium and magnesium as an insoluble trioxocarbonate IV salts.

CaCl2(aq) + Na2CO3(aq)

 

CaCO3(s) + 2NaCl(aq)

MgSO4(aq) + Na2CO3(aq)

MgCO3(s) + Na2SO4(aq)

 

 

 

 

ADVANTAGES OF HARD WATER             

  1. Does not dissolve lead pipes      
  2. Calcium and magnesium ion
  3. Useful for the body
  4. It gives water a pleasant taste

 

Disadvantages of hard water

  1. It forms scum with soap
  2. Wastes soap in washing
  3. When heated it form scales in pots and kettles

 

Hydrogen bond exist between water molecule which is an INTERMOLECULAR force of attraction given water its

  1. viscous nature
  2. surface tension
  3. latent heat of vapourization (the energy needed to turn water to steam).

 

Test for water

  1. Water will turn the white colour of anhydrous CuSO4 to blue hydrated CuSO4.5H2O
  2. Water will change the colour of blue dry CoCl2 into pink wet

CoCl2.6H20

 

Solubility

Solution is the homogenous mixture of two or more substances. Solute is the dissolved substance which may be solid, liquid or gas.

Solvent is the substance that dissolves the solute.

Saturated solution is the solution which contain as much solute a solution as it can dissolve at that given temperature in the presence of undissolved solute particle.

Unsaturated solution is solution which does not contain as much solute as it ought to contain at a given temperature

Supersaturated solution is a solution which contain as much solute than it can dissolve at that given temperature

Solubility of a solute in a solvent is defined as the amount of the solute in grammes which will dissolve in 1000g of the solvent, at a particular temperature.

Solubility is also defined as the maximum number in moles of the solute which will dissolve in 1000cm3/ 1dm3 of the solvent at a given temperature.

 

Water pollution

This is the contamination of water bodies as a result of human activities. The main cause of water pollution is the indiscriminate dumping of solid and liquid wastes into water bodies. It threatens aquatic life and changes water bodies in to foul smelling and unsightly scenes

 

Pollutants

  1. Refuse and sewage
  1. Industrial and agricultural wastes
  1. Crude oil spills

 

Control of water pollution

  1. Refuse should be buried or burnt in an incinerator or recycled
  1. Sewages should be processed to fertilizers
  1. Chemical wastes should be made biodegradable before disposal
  1. Safety measures should be implemented to prevent crude oil spills 
  1. Strict laws must be passed to control water pollution by individuals and companies

 

EVALUATION:    1. Define water

  1. List four sources and uses of water
  2. List three physical and chemical properties of water
  3. Define water pollution
  4. Give three examples of water pollutants
  5. How can water pollution be controlled?

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively