Lesson Note on Nitrogen Compounds: Oxides, Ammonia and Tests for Ammonia for SSS 2

Class: Senior Secondary School 2 (SS2 / SSS2)
Term: Second Term
Week: 11
Age: 16 years
Duration: 45 minutes
Subject: Chemistry
Curriculum Theme: Non-metals and their Compounds
Previous Lesson: Nitrogen: Uses and Nitrogen Cycle.
Topic: NITROGEN
Subject Matter: Compounds of nitrogen (oxides of nitrogen, ammonia), test for ammonia

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

• Identify and name various compounds of nitrogen.
• Describe the chemical test for ammonia gas.
• State the physical and chemical properties of ammonia.

Affective Domain:

• Appreciate the importance of ammonia in daily life and industry.
• Understand the need for safe handling of ammonia and other chemicals.

Psychomotor Domain:

• Perform the test for ammonia gas and record observations.
• Demonstrate a practical use of liquid ammonia in cleaning.

Social Domain:

• Participate actively in group discussions and practical demonstrations.
• Communicate their observations clearly during experiments.

Reference Materials

The following resources were used in planning this lesson:

• Senior Secondary Schools Education Curriculum
• State Unified Scheme of Work
• Uche, N. M. (2018). New School Chemistry for Senior Secondary Schools. Africana First Publishers Plc.
• https://www.waecdirect.org/
• https://www.neco.gov.ng/

Instructional Materials

The teacher will teach this lesson with the aid of:

• Glass with grease
• Painted wood work
• Samples of fertilizer
• Chemicals containing nitrogen (e.g., HNO3)
• Concentrated HCl
• Liquid ammonia
• Damp red litmus paper
• Test tubes and test tube rack

Rationale for the Lesson

This lesson helps pupils understand important nitrogen compounds like ammonia, which is essential for fertilizers and cleaning. It also teaches them practical skills in chemical testing and safe handling of substances.

Prerequisite/Previous Knowledge

Pupils have prior knowledge of elements, compounds, and the general properties of nitrogen from previous lessons.

Lesson Content/Board Summary

Compounds of Nitrogen

Oxides of Nitrogen

Nitrogen forms several oxides with oxygen, which are binary compounds. They have varying properties and uses. Examples include:

• Nitrous oxide (N₂O)
• Nitric oxide (NO)
• Dinitrogen trioxide (N₂O₃)
• Nitrogen dioxide (NO₂)
• Dinitrogen tetroxide (N₂O₄)
• Dinitrogen pentoxide (N₂O₅)

Ammonia (NH₃)

Ammonia is a colorless gas with a pungent, choking smell. It is lighter than air and highly soluble in water, forming ammonium hydroxide (NH₄OH), which is a weak base.

Physical Properties:

• Colorless gas
• Pungent, choking smell
• Lighter than air
• Very soluble in water
• Easily liquefied under pressure

Chemical Properties:

• Basic Nature: It is a weak base, turning damp red litmus paper blue.
• Reaction with Acids: Ammonia reacts with acids to form ammonium salts.
  Example: NH₃(g) + HCl(g) → NH₄Cl(s) (Ammonium chloride)
• Combustion: Ammonia does not burn in air but can burn in oxygen with a greenish-yellow flame.

Uses of Ammonia:

• Manufacture of fertilizers (e.g., ammonium sulphate, urea)
• Manufacture of nitric acid
• Refrigerant
• In household cleaners
• As a laboratory reagent

Test for Ammonia Gas

Ammonia gas can be tested using two main methods:

Method 1: Using damp red litmus paper

• Procedure: Bring a piece of damp red litmus paper to the mouth of a test tube containing the gas.
• Observation: The damp red litmus paper turns blue.
• Explanation: Ammonia dissolves in the water on the damp litmus paper to form ammonium hydroxide, which is alkaline and turns red litmus blue.

Method 2: Using concentrated hydrochloric acid (HCl)

• Procedure: Bring a glass rod dipped in concentrated hydrochloric acid near the mouth of a test tube containing the gas.
• Observation: Dense white fumes are produced.
• Explanation: Ammonia gas reacts with hydrogen chloride gas (from the concentrated HCl) to form solid ammonium chloride, which appears as dense white fumes.
  NH₃(g) + HCl(g) → NH₄Cl(s)

Safe Handling of Ammonia

Ammonia is corrosive and its fumes are toxic and irritating to the respiratory system and eyes. Always handle ammonia in a well-ventilated area or fume cupboard. Avoid direct inhalation and skin contact. Wear appropriate safety goggles and gloves.

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher asks pupils to name some common gases they know and introduces nitrogen as an important element that forms many compounds.
Pupils’ Activity: Pupils name common gases like oxygen, carbon dioxide, and air components. They listen attentively.
Learning Point: Pupils recall prior knowledge and are introduced to the topic of nitrogen compounds.

Step 2: Oxides of Nitrogen

Time: 7 minutes
Teaching Skill: Explanation/Discussion
Teacher’s Activity: The teacher guides pupils to identify and name various oxides of nitrogen, writing their formulas and briefly discussing their nature.
Pupils’ Activity: Pupils list examples of nitrogen oxides and copy notes from the board.
Learning Point: Pupils learn about different types of nitrogen oxides.

Step 3: Ammonia – Properties and Uses

Time: 10 minutes
Teaching Skill: Lecture/Explanation
Teacher’s Activity: The teacher explains the physical and chemical properties of ammonia and discusses its various uses in industry and everyday life.
Pupils’ Activity: Pupils listen, ask questions, and take notes on the properties and uses of ammonia.
Learning Point: Pupils understand the characteristics and importance of ammonia.

Step 4: Test for Ammonia (Demonstration)

Time: 8 minutes
Teaching Skill: Demonstration
Teacher’s Activity: The teacher demonstrates the test for ammonia gas using damp red litmus paper and a glass rod dipped in concentrated HCl, explaining the observations and chemical reactions.
Pupils’ Activity: Pupils observe the demonstration carefully and note down the procedures and expected results.
Learning Point: Pupils learn the practical method for identifying ammonia gas.

Step 5: Pupils Perform Test

Time: 7 minutes
Teaching Skill: Practical/Supervision
Teacher’s Activity: The teacher provides small samples of ammonium salt (to generate ammonia) and materials, guiding pupils to perform the ammonia test in groups.
Pupils’ Activity: Pupils, in groups, perform the ammonia test, record their observations, and discuss their findings.
Learning Point: Pupils gain hands-on experience in testing for ammonia and confirm its properties.

Step 6: Safe Handling of Ammonia and Practical Use

Time: 3 minutes
Teaching Skill: Practical Application/Safety
Teacher’s Activity: The teacher discusses the importance of safe handling of ammonia and demonstrates how liquid ammonia can be used to remove stains from painted woodwork or grease from glass.
Pupils’ Activity: Pupils listen to safety precautions and observe the practical application of ammonia.
Learning Point: Pupils learn about the hazards of ammonia and one of its practical uses.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

1. List three oxides of nitrogen.
2. State two physical properties of ammonia.
3. Describe how you would test for ammonia gas using damp red litmus paper.
4. Write the chemical equation for the reaction between ammonia gas and hydrogen chloride gas.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the importance of nitrogen compounds and their tests. The teacher then assigns homework.
Pupils’ Activity: Pupils listen to the summary and copy down the assigned homework.
Learning Point: Pupils consolidate their understanding of the lesson.

Lesson Keywords

• Nitrogen – A non-metallic element, symbol N.
• Oxides – Compounds formed between an element and oxygen.
• Ammonia – A colorless gas with a pungent smell, NH₃.
• Litmus paper – A paper used as an indicator for acidity or alkalinity.
• Ammonium chloride – A white crystalline salt formed from ammonia and hydrogen chloride, NH₄Cl.

Differentiation

For pupils who grasp concepts quickly, the teacher can provide additional questions on the industrial production of ammonia (Haber process). For those needing more support, the teacher will provide simplified definitions and more guided practice during the practical session.

Note for teachers using this lesson plan

Ensure all safety precautions are strictly followed during the demonstration and pupils’ practical activities involving ammonia and concentrated HCl. Adequate ventilation is crucial. Encourage pupils to ask questions and participate actively in discussions.