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Questions and Answers
Which of the following is a characteristic of physical changes?
What process can be used to obtain substances in pure state from solutions?
Which of the following processes is an example of a chemical change?
Which statement is correct regarding physical and chemical changes?
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Which of the following correctly identifies a characteristic of chemical changes?
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What is the height of the iron pillar near the Qutub Minar?
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How long ago was the iron pillar built?
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What remarkable feature does the iron pillar possess?
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What aspect of ancient Indian technology does the iron pillar highlight?
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How much does the iron pillar weigh?
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What substance is formed when carbon dioxide is passed through lime water?
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What is the chemical name of baking soda?
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Which of the following is NOT a method to prevent rusting of iron?
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What type of change occurs when baking soda is mixed with lemon juice and gas bubbles are formed?
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What is the main difference between burning wood and cutting wood into small pieces?
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Why does rusting of iron occur faster in coastal areas compared to deserts?
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What indicates that setting of curd is a chemical change?
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How are crystals of copper sulfate prepared?
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What is the role of painting iron to prevent rusting?
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What happens to the gas used in the kitchen when it exits the cylinder?
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Study Notes
Types of Changes
- Changes are classified into two main types: physical changes and chemical changes.
- Physical changes alter physical properties without creating new substances, often reversible.
- Chemical changes result in the formation of new substances, making them irreversible in many cases.
Key Processes
- Crystallisation allows the extraction of pure substances from solutions.
- Galvanisation involves coating iron with zinc to prevent rusting.
Examples of Changes
- Photosynthesis, burning of coal, and digestion of food are chemical changes.
- Dissolving sugar in water, melting wax, and beating aluminum into foil are physical changes.
True or False Statements
- Cutting wood is a physical change, not chemical.
- Manure formation from leaves is a chemical change, not physical.
- Zinc-coated iron pipes resist rusting due to galvanisation.
- Iron and rust are distinct substances.
- Condensation of steam is a physical change.
Fill in the Blanks
- Passing carbon dioxide through lime water forms calcium carbonate, causing cloudiness.
- Baking soda is chemically known as sodium hydrogen carbonate.
- Rusting can be mitigated by painting or galvanisation.
- Physical changes only alter physical properties, while chemical changes create new substances.
Chemical Changes Explained
- Mixing baking soda with lemon juice is a chemical change, producing carbon dioxide gas.
- Candle burning involves both physical changes (melting and evaporation of wax) and chemical changes (combustion).
Curd Setting as a Chemical Change
- Milk transforms into curd through fermentation, altering its chemical structure and properties.
Cutting vs. Burning Wood
- Cutting wood alters its size (physical change), while burning it changes its chemical composition, producing ash and gases (chemical change).
Copper Sulphate Crystallisation
- Dissolving copper oxide or carbonate in dilute sulfuric acid followed by evaporation leads to copper sulphate crystal formation.
Rust Prevention
- Painting iron surfaces forms a barrier against oxygen and moisture to prevent rust.
Rusting Conditions
- Rusting occurs faster in coastal areas due to saline moisture in the air, accelerating the corrosive process compared to arid desert regions.
Historical Context of Iron Technology
- The 1600-year-old iron pillar near Qutub Minar in Delhi showcases advanced rust-resistant technology from ancient India, having remained rust-free.
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Description
This quiz explores the differences between physical and chemical changes. You will learn about various processes such as crystallisation, galvanisation, and rusting. Test your understanding of these concepts and see how well you can distinguish between the two types of changes.
