Lab Activity: Fibre Identification by Tests MCQs Quiz | Class 9
This is a multiple-choice quiz for Class 9 Home Science (Code 064), Unit: Practical Exam Scheme. It covers the essential lab activity of fibre identification, focusing on physical characteristics and burning tests (3 marks). Please attempt all questions, click “Submit Quiz” to view your score, and then download the PDF answer sheet for your records.
Understanding Fibre Identification Tests
Identifying different types of fibres is a fundamental skill in Home Science. It is crucial for understanding fabric care, choosing appropriate textiles for different purposes, and quality assessment. The two primary methods used for simple identification in a lab setting are examining physical characteristics and performing a burning test.
1. Physical Characteristics Examination
This is the first step and involves observing the fibre’s properties using sight and touch. Key characteristics to note include:
- Lustre: How shiny or dull the fibre is. Silk has a high natural lustre, while cotton is typically dull.
- Texture: How the fibre feels. Wool feels warm and slightly coarse, silk is smooth, and cotton is soft and crisp.
- Strength: How easily the fibre breaks when pulled. Natural fibres like wool are generally weaker than synthetic fibres like nylon.
- Appearance: The visual look, including any crimp (waviness) or smoothness. Wool has a natural crimp, while synthetic fibres are often very uniform.
2. The Burning Test
The burning test is a more definitive method for identifying fibres. It involves carefully bringing a small sample of the fibre near a flame and observing its reaction. Different fibre groups (natural, synthetic) behave distinctly.
Safety First: Always perform this test under supervision, using tweezers to hold the fibre sample, and have a beaker of water nearby to extinguish the flame.
Fibre Burning Characteristics Table
| Fibre | Reaction to Flame | Odour when Burning | Residue / Ash |
|---|---|---|---|
| Cotton | Burns quickly, does not shrink from flame, continues to glow after flame is removed. | Like burning paper or leaves. | Fine, feathery grey or black ash. |
| Wool | Shrinks from flame, burns slowly, self-extinguishing (stops burning when flame is removed). | Like burning hair or feathers. | Brittle, black, irregular bead that crushes easily. |
| Silk | Curls away from flame, burns slowly, self-extinguishing. | Similar to burning hair, but less pronounced than wool. | Brittle, black, round bead that crushes to a powder. |
| Nylon | Melts and shrinks from flame, burns slowly with a sputtering flame. | Like celery or plastic. | Hard, black, round bead that is difficult to crush. |
| Polyester | Melts and shrinks from flame, may drip hot plastic, burns with a black smoke. | Slightly sweet, chemical odour. | Hard, black, irregular bead that is difficult to crush. |
Quick Revision Points
- Natural Plant Fibre (Cellulosic): Cotton burns like paper and leaves a soft ash.
- Natural Animal Fibre (Protein): Wool and Silk burn like hair, are self-extinguishing, and leave a crushable black bead.
- Synthetic Fibres: Nylon and Polyester melt, shrink from the flame, and form a hard, uncrushable bead.
- The smell is a key differentiator: burning paper (cotton), burning hair (wool/silk), chemical/celery (nylon/polyester).
- Physical feel is a good preliminary test: cotton is soft, wool is warm, silk is smooth, and synthetics feel manufactured.
Extra Practice Questions
- You are given a fabric that feels very smooth and has a high shine. In a burning test, it curls from the flame and smells like burning feathers. What is it most likely to be?
- A fibre sample burns very rapidly with a smell of burning leaves and leaves a grey, feathery ash. Which fibre is it?
- Why is it important to know the difference between natural and synthetic fibres when ironing clothes?
- If a fibre melts into a hard black bead that is difficult to crush, is it more likely to be a natural or a synthetic fibre?
- Describe the difference in texture you would expect to feel between a 100% cotton fabric and a 100% wool fabric.
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