Chemical Change MCQs Quiz | Class 9
Class IX Science (Code 086), Unit I: Matter – Its Nature and Behaviour. This quiz covers the meaning of chemical changes, real-life examples like rusting and burning, and the formation of new substances. Test your knowledge and download the solution PDF.
Understanding Chemical Changes
A chemical change is a process where one or more substances are altered into one or more new and different substances. Unlike physical changes, chemical changes involve a reorganization of atoms and are usually permanent and irreversible.
Key Characteristics
- Formation of New Substances: The products formed have entirely different properties from the reactants.
- Energy Change: Heat or light is often absorbed or released (exothermic or endothermic reactions).
- Irreversibility: Most chemical changes cannot be reversed by simple physical means.
- Change in Composition: The chemical formula of the substance changes.
Common Examples
- Rusting of Iron: Iron reacts with oxygen and moisture to form reddish-brown hydrated iron oxide (rust).
- Burning (Combustion): Burning paper, wood, or fuels produces ash, smoke, and gases like carbon dioxide.
- Cooking Food: Heating alters the chemical structure of proteins and carbohydrates.
- Curdling of Milk: Bacteria convert lactose into lactic acid, forming curd.
Comparison: Physical vs Chemical Change
| Feature | Physical Change | Chemical Change |
|---|---|---|
| New Substance | No new substance formed | One or more new substances formed |
| Reversibility | Usually reversible | Usually irreversible |
| Example | Melting ice, tearing paper | Burning wood, rusting iron |
Quick Revision Points
- A chemical change is also called a chemical reaction.
- Indicators of chemical change: evolution of gas, change in color, change in temperature, formation of precipitate.
- Reactants are starting materials; Products are the new materials formed.
Extra Practice Questions
- Why is the ripening of fruit considered a chemical change?
- Is the burning of a candle both a physical and chemical change? Explain.
- What new substance is formed when magnesium ribbon burns in air?
- Differentiate between evaporation of water and electrolysis of water.
- Write the word equation for the rusting of iron.
