Chemical Hazards, Common Laboratory Hazards and Laboratory Safety Rules for SS 1

Class: SS 1
Term: First Term
Week: 7
Age: 15 years
Duration: 60 minutes
Subject: Chemistry
Curriculum Theme: The chemical world
Focal competence: Acquiring information on safety and ways of preventing hazards associated with chemicals
Key competencies/values: Collaboration; Information Literacy
Skills:

• Handling, storing, and disposing chemicals properly

Previous Lesson: Separation Techniques and Their Applications
Topic: Chemical Hazards
Subject Matter: Meaning of chemical hazards, Description of common Laboratory hazards, State, safety rules in the, laboratory

Specific Objectives

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

Cognitive Domain

• state the meaning of chemical hazards;
• name common chemical hazards;
• identify laboratory hazards;
• identify the symbols of common laboratory hazards.

Affective Domain

• appreciate the importance of laboratory safety rules;
• collaborate effectively during laboratory hazard identification.

Psychomotor Domain

• carefully handle chemical bottles;
• demonstrate correct handling of laboratory apparatus.

Reference Materials

The following resources were used in planning this lesson:

• 2025 New Revised Senior Secondary Education Curriculum (SSEC)
• Relevant State Unified Scheme of Work
• Essential Chemistry for Senior Secondary Schools by O. Y. Ababio
• The HeadTeacher Scheme of work For The New Revised Senior Secondary Education Curriculum (SSEC)

Instructional Materials

The teacher will teach this lesson with the aid of:

• The school laboratory
• Packages and bottles of laboratory chemicals
• Video clips on chemicals, associated hazards and safety precautions
• A chart on chemical hazards and their symbols
• CD or DVD player
• Projector (if available)

Rationale for the Lesson

This lesson is crucial for ensuring students understand the potential dangers in a chemistry laboratory and how to prevent accidents. It equips them with the knowledge and skills to identify, handle, and respond to chemical hazards safely, fostering a responsible and secure learning environment.

Prerequisite/Previous Knowledge

Students should have basic knowledge of the school laboratory environment and general classroom safety rules.

Lesson Content/Board Summary

Chemical Hazards

Meaning of Chemical Hazards

Chemical hazards refer to any chemical substance that can cause harm to humans, animals, or the environment due to its inherent properties. These properties include flammability, corrosivity, toxicity, reactivity, or explosivity.

Common Laboratory Hazards

Laboratory hazards are potential sources of harm or danger present in a laboratory setting. These can be broadly categorised as:

1. Chemical Hazards: Substances that are toxic, corrosive, flammable, reactive, or explosive. Examples include strong acids (e.g., concentrated sulphuric acid), strong bases (e.g., sodium hydroxide), organic solvents (e.g., ethanol, acetone), and oxidising agents (e.g., hydrogen peroxide).
2. Physical Hazards: Dangers from equipment, electricity, heat, cold, pressure, or sharp objects. Examples include broken glassware, electrical shocks, hot plates, open flames, and high-pressure gas cylinders.
3. Biological Hazards: Risks from living organisms or their products. While less common in general chemistry, these can include bacteria, viruses, fungi, or biological toxins if biological samples are handled.
4. Ergonomic Hazards: Risks from poor workstation design or repetitive tasks. Examples include improper posture while working at a bench or repetitive pipetting.

Symbols of Common Laboratory Hazards

Hazard symbols are pictograms used to convey information about the dangers of a chemical substance. Understanding these symbols is essential for safe handling.

1. Flammable: Indicates substances that can easily catch fire or ignite. (e.g., a flame pictogram)
2. Corrosive: Indicates substances that can cause severe skin burns and eye damage, or are corrosive to metals. (e.g., a hand and surface being corroded)
3. Toxic/Poisonous: Indicates substances that can cause death or severe health effects if swallowed, inhaled, or absorbed through the skin. (e.g., a skull and crossbones)
4. Irritant/Harmful: Indicates substances that can cause skin irritation, eye irritation, or other less severe health effects. (e.g., an exclamation mark)
5. Oxidising: Indicates substances that can cause or intensify a fire or explosion by releasing oxygen. (e.g., a flame over a circle)
6. Explosive: Indicates substances that can explode under certain conditions (e.g., heat, shock, friction). (e.g., an exploding bomb)
7. Environmental Hazard: Indicates substances that are harmful to the aquatic environment. (e.g., a dead fish and tree)
8. Gas Under Pressure: Indicates gases stored under pressure, which may explode if heated. (e.g., a gas cylinder)

Standard Precautions for Handling Chemicals

To ensure safety when working with chemicals, the following precautions should always be observed:

1. Always wear appropriate Personal Protective Equipment (PPE), such as safety goggles, laboratory coats, and gloves.
2. Read chemical labels carefully before use to understand hazards and handling instructions.
3. Never taste or smell chemicals directly. If smelling is necessary, waft a small amount of vapour towards your nose.
4. Handle chemicals in a well-ventilated area or under a fume hood, especially volatile or toxic substances.
5. Use the smallest practical quantities of chemicals.
6. Always add acid to water slowly, never water to concentrated acid, to avoid violent reactions.
7. Keep chemical containers closed when not in use to prevent spills, evaporation, and contamination.
8. Store chemicals properly according to their compatibility and hazard class (e.g., acids separate from bases, flammables in a fire cabinet).
9. Dispose of chemical waste according to laboratory guidelines, never pour chemicals down the drain unless specifically instructed.
10. Wash hands thoroughly with soap and water after handling chemicals and before leaving the laboratory.

Laboratory Safety Rules

Adhering to general safety rules is paramount for preventing accidents in the laboratory:

1. Always follow the teacher’s instructions carefully and do not perform unauthorised experiments.
2. Never work alone in the laboratory.
3. Know the location and proper use of safety equipment, such as fire extinguishers, fire blankets, eyewash stations, and emergency showers.
4. Report all accidents, spills, or broken equipment to the teacher immediately, no matter how minor.
5. Keep your work area clean and tidy. Clear away unnecessary items.
6. Do not eat, drink, or chew gum in the laboratory. Never apply cosmetics.
7. Tie back long hair, secure loose clothing, and remove dangling jewellery.
8. Wear closed-toe shoes; avoid sandals or open-toed footwear.
9. Do not run or engage in horseplay in the laboratory.
10. Ensure all electrical cords are in good condition and keep them away from water sources.
11. Never point the open end of a test tube containing a reacting mixture towards yourself or others.
12. Before leaving the laboratory, ensure all gas taps are turned off, water taps are closed, and electrical equipment is switched off and unplugged.

Teaching Methods/Instructional Techniques

Discussion, Demonstration, Guided Practice, Question and Answer, Explanation, Observation, Group Work, Practical Activity

Instructional Procedures

Step 1: Introduction

Time: 5 minutes

Teaching Skill: Questioning/Engagement

Teacher’s Activity: The teacher greets the students and asks them about their understanding of safety in everyday life and why it is important. The teacher then introduces the topic: Chemical Hazards and Laboratory Safety.

Pupils’ Activity: Pupils respond to the questions and listen attentively to the introduction of the topic.

Learning Point: Importance of safety

Step 2: Meaning of Chemical Hazards

Time: 10 minutes

Teaching Skill: Explanation/Discussion

Teacher’s Activity: The teacher explains the meaning of chemical hazards, giving examples of properties that make chemicals hazardous (flammable, corrosive, toxic, etc.). The teacher encourages students to contribute their ideas.

Pupils’ Activity: Pupils listen, ask questions, and contribute to the discussion on the meaning of chemical hazards.

Learning Point: Definition of chemical hazards

Step 3: Identification of Common Laboratory Hazards

Time: 10 minutes

Teaching Skill: Guided Observation/Demonstration

Teacher’s Activity: The teacher guides students on a tour of the school laboratory. During the tour, the teacher points out various potential hazards, including chemical bottles, glassware, electrical outlets, and heat sources, and discusses them with the students.

Pupils’ Activity: Pupils observe the laboratory environment, identify potential hazards, and ask questions about them.

Learning Point: Recognition of laboratory hazards

Step 4: Examining Chemical Packages and Hazard Symbols

Time: 10 minutes

Teaching Skill: Practical Application/Explanation

Teacher’s Activity: The teacher guides students to examine packages and bottles of chemicals in the laboratory. Using the hazard chart, the teacher explains the symbols of common laboratory hazards and their implications for safety.

Pupils’ Activity: Pupils examine chemical labels, identify hazard symbols, and match them with the explanations on the chart.

Learning Point: Hazard symbols identification

Step 5: Standard Precautions for Handling Chemicals

Time: 5 minutes

Teaching Skill: Explanation/Instruction

Teacher’s Activity: The teacher explains the standard precautions for handling chemicals, such as wearing PPE, reading labels, proper mixing techniques (acid to water), and ventilation. The teacher demonstrates careful handling of an empty chemical bottle.

Pupils’ Activity: Pupils listen and observe the demonstration, noting the precautions discussed.

Learning Point: Chemical handling precautions

Step 6: Laboratory Safety Rules

Time: 5 minutes

Teaching Skill: Discussion/Reinforcement

Teacher’s Activity: The teacher leads a discussion on general laboratory safety rules, encouraging students to recall and state rules they already know. The teacher reinforces the importance of each rule.

Pupils’ Activity: Pupils participate in the discussion, stating and explaining various laboratory safety rules.

Learning Point: Understanding safety rules

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. What is a chemical hazard?
2. Name three common laboratory hazards.
3. Identify the meaning of the “skull and crossbones” hazard symbol.
4. State two standard precautions for handling chemicals.
5. Mention two important laboratory safety rules.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Chemical hazard knowledge assessed

Step 8: Note-Taking

Time: 10 minutes

Teaching Skill: Guided Writing

Teacher’s Activity: The teacher guides pupils/students to copy the essential Board Summary notes on chemical hazards, common laboratory hazards, and safety rules into their notebooks.

Pupils’ Activity: Pupils/students copy the notes carefully into their notebooks.

Learning Point: Recording lesson notes

Step 9: Conclusion

Time: 5 minutes

Teaching Skill: Summarisation

Teacher’s Activity: The teacher summarises the key points of the lesson, re-emphasising the importance of safety in the laboratory and encouraging students to always be vigilant and responsible when handling chemicals and apparatus. The teacher reminds them that safety is everyone’s responsibility.

Pupils’ Activity: Pupils listen and ask any final clarifying questions.

Learning Point: Reinforcement of safety importance

Continuous Assessment/Further Study

Type: Homework/Further Reading

Instruction: Answer the following questions in your notebook and research additional information on chemical spills.

1. List five different hazard symbols and explain what each one signifies.
2. Why is it important to wear a laboratory coat and safety goggles when working with chemicals?
3. Describe the correct procedure for diluting a concentrated acid.
4. Research and write a short paragraph on what to do in case of a minor chemical spill in the laboratory.

Lesson Keywords

• Chemical Hazard – A chemical substance that can cause harm.
• Flammable – Easily catches fire.
• Corrosive – Causes damage to skin, eyes, or materials.
• Toxic – Poisonous; can cause severe harm or death.
• Oxidising – Helps other substances burn or explode.
• PPE – Personal Protective Equipment (e.g., goggles, lab coat, gloves).
• Fume Hood – A ventilated enclosure to remove hazardous fumes.

Differentiation

For students who grasp concepts quickly, encourage them to research specific chemical accidents and their causes. Provide additional visual aids and simplified explanations for students who may struggle with identifying hazard symbols or understanding complex safety procedures. Pair stronger students with weaker ones during the lab tour and identification activities to foster peer learning and collaboration.

Suggested Lesson Videos

For videos on chemical hazards and laboratory safety rules, search on YouTube for: SS1 Chemistry chemical hazards laboratory safety rules nigeria