Classify Physical/Chemical Change: Mg Burning MCQs Quiz | Class 9
This Class IX Science (Code 086) quiz covers Unit I: Practicals, specifically focusing on the observation-based classification of burning magnesium ribbon in air. Test your understanding of observations, chemical reactions, and properties of the ash formed. Attempt all 10 MCQs, check your score, and download the PDF solution for revision.
Topic Overview: Burning of Magnesium Ribbon
Burning magnesium ribbon in air is a classic example of a chemical change. This experiment is part of the Class 9 Science practical syllabus (Unit I) to distinguish between physical and chemical changes based on observations.
Key Observations
- Flame: Magnesium burns with a dazzling white flame.
- Product: It leaves behind a white powder called Magnesium Oxide (MgO).
- Heat: A significant amount of heat and light is evolved, making it an exothermic reaction.
Chemical Reaction
The reaction involves the combination of magnesium with oxygen from the air. It is also classified as a combination reaction.
Equation: 2Mg (s) + O2 (g) → 2MgO (s)
Nature of the Product
The white ash (Magnesium Oxide) is basic in nature. When dissolved in water, it forms Magnesium Hydroxide, which turns red litmus paper blue.
Reaction with water: MgO + H2O → Mg(OH)2
Summary Table
| Parameter | Observation/Fact |
|---|---|
| Type of Change | Chemical Change |
| Reactants | Magnesium ribbon and Oxygen |
| Visual Observation | Dazzling white light |
| Residue | White powder (MgO) |
| Nature of Oxide | Basic (Red litmus turns Blue) |
Precautions
- Clean the magnesium ribbon with sandpaper before burning to remove the layer of carbonate or oxide formed due to slow reaction with moist air.
- Hold the ribbon with a pair of tongs.
- Do not look directly at the dazzling flame for too long as it can be harmful to the eyes.
Extra Practice Questions
- Why is the burning of magnesium considered a chemical change? (Ans: New substance MgO is formed with different properties)
- What happens if the magnesium ribbon is not cleaned before burning? (Ans: It may not burn properly due to the interfering oxide layer)
- Is the mass of the ash formed equal to the mass of the magnesium ribbon burnt? (Ans: No, the mass increases due to the addition of oxygen)
- What is the state of Magnesium Oxide at room temperature? (Ans: Solid)
- Name the type of reaction based on energy exchange. (Ans: Exothermic reaction)
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