Lesson Notes By Weeks and Term - Senior Secondary 2

Water II

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TERM: 2ND TERM

WEEK TWO

Class: Senior Secondary School 2

Age: 16 years

Duration: 40 minutes of 5 periods each

Date:        

Subject: Chemistry

Topic:-        WATER II

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

  1. define water hardness and identify its causes.
  2. Identify the two types of water hardness.
  3. Identify the possible ways of addressing the issue of water hardness.
  4. Identify methods of purifying water and also producing distilled 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 refreshes the students knowledge about water.

Students pay attention

STEP 2

EXPLANATION

He explains water hardness, its causes, types of water hardness and its effects.

 

Students pay attention and participates

STEP 3

DEMONSTRATION

He discusses the possible ways of addressing  the issue of water hardness.

Students pay attention and participate

STEP 4

DEMONSTRATION

Teacher explains the methods of purifying water and also producing distilled water.

Students pay attention and participate

STEP 5

NOTE TAKING

The teacher writes a summarized note on the board

The students copy the note in their books

 

NOTE

WATER 2

Hardness of water

Water hardness is a measure of the concentration of divalent metal ions, primarily calcium (Ca2+) and magnesium (Mg2+), in water. These ions can make water "hard" by forming insoluble compounds, typically with carbonate and sulfate ions.

- Temporary Hardness: Caused by dissolved bicarbonate minerals (HCO3-) and can be removed by boiling, which converts bicarbonates to insoluble carbonates.

- Permanent Hardness: Caused by the presence of sulfate and chloride salts of calcium and magnesium. It can't be removed by boiling.

Hard water can lead to scale buildup in pipes and appliances and may affect the lathering of soap.

The hardness of water is commonly measured in terms of milligrams of calcium carbonate per liter (mg/L) or parts per million (ppm). Water hardness is classified as soft (0-60 mg/L), moderately hard (61-120 mg/L), hard (121-180 mg/L), and very hard (greater than 180 mg/L).

Water hardness can be addressed through various methods:

  1. Boiling: Boiling is effective for removing temporary hardness. It causes the precipitation of calcium carbonate, and the insoluble precipitate can be separated from the water.
  2. Water Softeners: Ion exchange water softeners are commonly used. These systems replace calcium and magnesium ions with sodium ions, reducing the overall hardness of the water. However, this may increase sodium levels in the water, which can be a concern for individuals on sodium-restricted diets.
  3. Lime Softening: This method involves adding lime (calcium hydroxide) to water, which reacts with the hardness ions, forming precipitates that can be removed.
  4. Distillation: Distillation involves boiling water and then condensing the steam back into water. This process effectively removes minerals, including hardness ions, leaving them behind in the boiling chamber.
  5. Reverse Osmosis: This process uses a semipermeable membrane to remove ions, molecules, and larger particles from water, reducing hardness among other impurities.

Purification of water

Water purification involves removing contaminants to make water safe for consumption. Common methods include:

  1. Filtration: This process involves passing water through a filter to remove particles and impurities. Filtration methods range from simple cloth filters to advanced membrane filtration systems.
  2. Boiling: Boiling water kills bacteria, viruses, and parasites, making it safe to drink. It's a simple and effective method but may not remove chemical contaminants.
  3. Chlorination: Adding chlorine or chlorine-based compounds to water kills bacteria and other pathogens. It's a widely used method for disinfecting water in municipal systems.
  4. UV Purification; Ultraviolet (UV) light is used to kill or inactivate microorganisms in water. It is effective against bacteria, viruses, and parasites without adding chemicals.
  5. Reverse Osmosis: This process uses a semipermeable membrane to remove ions, molecules, and larger particles, providing a high level of purification.

Production of distilled water

The production of distilled water involves a process called distillation. Here's a basic overview of the steps:

  1. Boiling: Water is heated to its boiling point, turning it into steam. This process is designed to separate water molecules from contaminants and impurities.
  2. Condensation: The steam is then cooled and condensed back into liquid water. This is usually done in a separate chamber or through the use of a condensation coil.
  3. Collection: The condensed water, now purified, is collected. This water is considered distilled because it has been separated from impurities, minerals, and other substances during the distillation process.

EVALUATION:   1. Explain the concept, water hardness?

  1. Identify the two types of water hardness.
  2. Identify 4 ways of tackling water hardness.
  3. Mention 3 ways of purifying water.

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively