Separation Techniques and Their Applications for SS 1

Class: SS 1
Term: First Term
Week: 6
Age: 15 years
Duration: 60 minutes
Subject: Chemistry
Curriculum Theme: The chemical world
Focal competence: Apply relevant techniques for the separation of mixtures
Key competencies/values: Research and Problemsolving
Skills:

• Handling (setting up) of apparatus for the separation of mixtures

Previous Lesson: Branches of Chemistry, Their Focus and Importance
Topic: Standard Separation Techniques
Subject Matter: Meaning of separation techniques, Separation techniques

Specific Objectives

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

Cognitive Domain

• Define separation techniques.
• Explain the terms associated with separation techniques.
• Identify substances that require separation.
• Discuss ways of separating substances into their components.

Affective Domain

• Appreciate the importance of separation techniques in daily life and industry.
• Participate actively in group discussions on separation principles.

Psychomotor Domain

• Name the apparatus for separating various substances.
• Demonstrate the use of different techniques to separate simple mixtures.
• Separate common mixtures into their components using appropriate techniques.

Social Domain

• Collaborate effectively in groups to discuss separation principles.

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
• 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:

• Video clips demonstrating different separation techniques.
• Beakers, funnels, filter paper, evaporating dish, Bunsen burner, tripod stand, gauze.
• Samples of mixtures (e.g., sand and salt, oil and water, coloured solution).
• Paper, pencil, marker.
• School chemistry textbook.

Rationale for the Lesson

This lesson is important as it introduces students to practical methods of separating components of mixtures, a fundamental concept in chemistry. Understanding these techniques helps students appreciate how pure substances are obtained and applied in various fields, from laboratories to industries and everyday life. It also develops critical thinking and problem-solving skills in identifying appropriate separation methods.

Prerequisite/Previous Knowledge

Students should have prior knowledge of matter, elements, compounds, and mixtures, including the differences between homogeneous and heterogeneous mixtures.

Lesson Content/Board Summary

Standard Separation Techniques

Meaning of Separation Techniques

Separation techniques are physical or chemical methods used to separate mixtures into their individual components or pure substances. These techniques exploit the differences in physical or chemical properties of the components in the mixture, such as boiling points, solubility, particle size, density, or magnetic properties.

Types of Separation Techniques

1. Filtration

Filtration is a technique used to separate an insoluble solid from a liquid or solution. It is based on the difference in particle size between the solid and the liquid.

1. Principle: The mixture is passed through a filter medium (e.g., filter paper) that allows the liquid (filtrate) to pass through, while retaining the solid particles (residue).
2. Apparatus: Funnel, filter paper, beaker, retort stand.
3. Examples:
   1. Separating sand from water.
   2. Separating chalk powder from water.
   3. Brewing coffee or tea, where the coffee grounds or tea leaves are the residue and the brewed liquid is the filtrate.
4. Observable Properties: The solid remains on the filter paper, and a clear liquid passes through.

2. Evaporation

Evaporation is a technique used to separate a soluble solid from a solvent, typically when the solid is non-volatile and the solvent is volatile.

1. Principle: The solvent is heated and allowed to vaporise, leaving the solid component behind. This method is suitable when the solid is stable to heat and the solvent is not required.
2. Apparatus: Evaporating dish, Bunsen burner, tripod stand, gauze.
3. Examples:
   1. Obtaining salt from a salt solution (brine).
   2. Separating sugar from a sugar solution.
4. Observable Properties: The liquid disappears as vapour, and a solid crystalline or powdered substance is left behind.

3. Crystallization

Crystallization is a separation technique used to purify solids by forming crystals from a solution. It is based on differences in solubility of the components at different temperatures.

1. Principle: A hot saturated solution of the impure solid is prepared. As the solution cools, the desired substance crystallizes out, while impurities remain in the solution. The crystals are then filtered and dried.
2. Apparatus: Beaker, heating apparatus (Bunsen burner, tripod stand, gauze), stirring rod, filter paper, funnel.
3. Examples:
   1. Obtaining pure copper(II) sulphate crystals from an impure solution.
   2. Purifying sugar or salt.
4. Observable Properties: Formation of distinct solid crystals as the solution cools.

4. Fractional Crystallization

Fractional crystallization is a method used to separate two or more soluble solids that have different solubilities in the same solvent at different temperatures.

1. Principle: A hot concentrated solution containing the mixture of solids is cooled slowly. The solid with lower solubility at a given temperature will crystallize out first, leaving the more soluble components in solution. This process can be repeated to achieve better separation.
2. Apparatus: Beaker, heating apparatus, stirring rod, filter paper, funnel.
3. Examples:
   1. Separating a mixture of potassium nitrate and sodium chloride. Potassium nitrate is much more soluble in hot water than in cold water, while sodium chloride’s solubility changes little with temperature.
   2. Purification of crude drugs.
4. Observable Properties: Different solids crystallize at different temperatures as the solution cools.

5. Decantation

Decantation is a simple method used to separate immiscible liquids or a liquid from a solid that has settled at the bottom of a container.

1. Principle: It relies on the difference in density between the components. For a solid-liquid mixture, the denser solid settles, and the liquid is carefully poured off. For immiscible liquids, the denser liquid settles below the less dense liquid, and the upper layer is carefully poured off.
2. Apparatus: Beaker, separating funnel (for immiscible liquids).
3. Examples:
   1. Separating sand from water after the sand has settled.
   2. Separating oil from water using a separating funnel.
4. Observable Properties: Clear separation of layers or settled solid, allowing one component to be poured off.

6. Sublimation

Sublimation is a process where a solid changes directly into a gas without passing through the liquid phase, and vice versa.

1. Principle: This technique is used to separate a sublimable solid from a non-sublimable solid. When heated, the sublimable component turns into a gas and then solidifies upon cooling, leaving the non-sublimable component behind.
2. Apparatus: Evaporating dish, funnel, Bunsen burner, tripod stand, gauze, watch glass (for cooling).
3. Examples:
   1. Separating iodine from sand.
   2. Separating ammonium chloride from sodium chloride.
   3. Separating naphthalene from common salt.
4. Observable Properties: The sublimable solid disappears upon heating and reappears as a solid on a cool surface.

7. Distillation

Distillation is a process used to separate components of a liquid mixture based on differences in their boiling points.

1. Principle: The mixture is heated, causing the component with the lower boiling point to vaporize first. The vapour is then cooled and condensed back into a liquid (distillate), leaving the component with the higher boiling point behind.
2. Apparatus: Distillation flask, condenser, receiver, thermometer, heating mantle/Bunsen burner.
3. Types:
   1. Simple Distillation: Used to separate a volatile liquid from a non-volatile solute (e.g., salt solution) or two liquids with significantly different boiling points (difference of at least 25°C).
   2. Fractional Distillation: Used to separate two or more miscible liquids with close boiling points (difference less than 25°C). A fractionating column is used to provide a large surface area for repeated vaporization and condensation.
4. Examples:
   1. Obtaining pure water from saltwater (simple distillation).
   2. Separating ethanol from water (fractional distillation).
   3. Separation of crude oil into its fractions (fractional distillation).
5. Observable Properties: Liquid boils, vapour forms, condenses back to liquid in a separate container.

8. Chromatography

Chromatography is a powerful analytical technique used to separate components of a mixture based on their differential distribution between a stationary phase and a mobile phase.

1. Principle: Components of a mixture travel at different speeds through a stationary phase (e.g., paper, silica gel) due to differences in their adsorption to the stationary phase and solubility in the mobile phase (solvent).
2. Apparatus: Chromatographic paper/plate, solvent, beaker/jar, pencil.
3. Types: Paper chromatography, Thin-layer chromatography, Column chromatography, Gas chromatography.
4. Examples:
   1. Separating different coloured dyes in ink.
   2. Separating amino acids.
   3. Detecting banned substances in sports.
5. Observable Properties: Components separate into distinct bands or spots on the stationary phase.

9. Magnetic Separation

Magnetic separation is used to separate magnetic substances from non-magnetic substances.

1. Principle: A magnet is passed over the mixture, attracting the magnetic component and leaving the non-magnetic component behind.
2. Apparatus: Magnet.
3. Examples:
   1. Separating iron filings from sand.
   2. Separating iron from sulphur powder.
4. Observable Properties: Magnetic material sticks to the magnet, non-magnetic material remains.

Teaching Methods/Instructional Techniques

Discussion, Demonstration, Guided Practice, Question and Answer, Explanation, Observation, Group Work, Video Presentation.

Instructional Procedures

Step 1: Introduction

Time: 5 minutes

Teaching Skill: Activating Prior Knowledge/Engagement

Teacher’s Activity: The teacher greets the students and asks them to recall what they learned about mixtures in their previous classes. The teacher then introduces the topic by asking students how they would separate common mixtures like sand and water, or salt and water.

Pupils’ Activity: Pupils respond to the teacher’s questions and share their ideas on separating mixtures.

Learning Point: Prior knowledge activation

Step 2: Meaning of Separation Techniques

Time: 10 minutes

Teaching Skill: Explanation/Definition

Teacher’s Activity: The teacher explains the meaning of separation techniques, emphasizing that they are methods to separate mixtures based on differences in physical or chemical properties. The teacher provides simple examples to illustrate the concept.

Pupils’ Activity: Pupils listen attentively, ask questions for clarification, and define separation techniques in their own words.

Learning Point: Definition of separation techniques

Step 3: Video Presentation on Separation Techniques

Time: 10 minutes

Teaching Skill: Visual Learning/Observation

Teacher’s Activity: The teacher guides students to watch short video clips demonstrating various separation techniques such as filtration, evaporation, decantation, and distillation. The teacher pauses the videos to highlight key apparatus and observable changes.

Pupils’ Activity: Pupils watch the videos, observe the processes, and identify the techniques and apparatus shown.

Learning Point: Identification of techniques and apparatus

Step 4: Group Discussion on Principles and Apparatus (Part 1)

Time: 10 minutes

Teaching Skill: Group Collaboration/Facilitation

Teacher’s Activity: The teacher divides students into groups and assigns each group 1-2 separation techniques (e.g., Filtration, Evaporation, Crystallization, Fractional Crystallization, Decantation). The teacher instructs them to discuss the principle behind each technique and identify the apparatus used, based on the videos and their textbooks.

Pupils’ Activity: Pupils discuss in their groups, identifying principles and apparatus for their assigned techniques.

Learning Point: Principles of separation techniques

Step 5: Group Discussion on Principles and Apparatus (Part 2)

Time: 5 minutes

Teaching Skill: Group Collaboration/Facilitation

Teacher’s Activity: The teacher continues to monitor group discussions, providing guidance and clarifying misconceptions about techniques like Sublimation, Distillation, Chromatography, and Magnetic Separation.

Pupils’ Activity: Groups continue their discussions, focusing on the remaining techniques and preparing to present their findings.

Learning Point: Apparatus for separation

Step 6: Group Presentations and Teacher Reinforcement

Time: 5 minutes

Teaching Skill: Presentation/Reinforcement

Teacher’s Activity: Each group briefly presents their findings on the principles and apparatus for their assigned techniques. The teacher provides further explanations, clarifies chemical terms, and gives practical examples for each technique, ensuring safe interpretation.

Pupils’ Activity: Groups present their findings. Pupils listen to other groups and ask questions.

Learning Point: Understanding various techniques

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 are separation techniques?
2. Mention two techniques used to separate a solid from a liquid.
3. Name the main apparatus used for filtration.
4. Explain the principle behind fractional crystallization.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Assessment of understanding

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 the meaning and types of separation techniques into their notebooks.

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

Learning Point: Recording lesson content

Step 9: Conclusion

Time: 5 minutes

Teaching Skill: Consolidation

Teacher’s Activity: The teacher summarises the key points of the lesson, reiterating the importance of understanding different separation techniques and their applications in everyday life. The teacher encourages students to observe separation processes around them.

Pupils’ Activity: Pupils listen to the summary and ask any final questions.

Learning Point: Lesson consolidation

Continuous Assessment/Further Study

Type: Homework/Practice Exercise

Instruction: Answer the following questions in your notebook.

1. Differentiate between evaporation and crystallization, stating one situation where each would be preferred.
2. Suggest an appropriate separation technique for each of the following mixtures and state the principle involved:
   1. Iron filings and sulphur powder
   2. Ink dyes
   3. Salt and water
   4. Oil and water
3. Draw and label the apparatus setup for simple distillation.

Lesson Keywords

• Mixture – A substance containing two or more substances not chemically combined.
• Separation Techniques – Methods used to isolate components of a mixture.
• Filtration – Separating insoluble solid from liquid using a filter medium.
• Evaporation – Separating soluble non-volatile solid from volatile solvent by heating.
• Crystallization – Obtaining pure solid crystals from a solution.
• Fractional Crystallization – Separating soluble solids with different solubilities.
• Decantation – Separating immiscible liquids or a liquid from a settled solid.
• Sublimation – Solid changing directly to gas and back without liquid phase.
• Distillation – Separating liquids based on boiling point differences.
• Chromatography – Separating components based on differential distribution between phases.
• Magnetic Separation – Separating magnetic substances from non-magnetic ones.

Differentiation

For students needing support, provide simplified diagrams of each technique and pre-label key apparatus. Pair them with stronger students during group discussions. For advanced learners, challenge them to research industrial applications of these techniques or design an experiment to separate a complex mixture with multiple components.

Suggested Lesson Videos

Search on YouTube for: separation techniques chemistry SS1