Nature of Matter: Compounds MCQs Quiz | Class 9
This quiz for Class IX Science (Code 086) focuses on Unit I: Matter – Its Nature and Behaviour. The specific topic covered is the nature of compounds, including the concept of compounds, their fixed composition, and relevant examples. Test your understanding of how elements combine chemically to form new substances. Upon completion, submit your answers to view your score and download the PDF answer key for revision.
Understanding Compounds in Matter
In Class 9 Science, Unit I (Matter – Its Nature and Behaviour), a compound is defined as a pure substance composed of two or more elements chemically combined in a fixed proportion by mass. Unlike mixtures, compounds have distinct properties different from their constituent elements.
Key Characteristics of Compounds
- Fixed Composition: The elements in a compound are always present in a definite ratio by mass (law of constant proportions). For example, water (H2O) always contains hydrogen and oxygen in the ratio of 1:8 by mass.
- Chemical Bonding: The constituents are held together by strong chemical bonds.
- New Properties: The properties of a compound are entirely different from those of its constituent elements. For instance, Sodium is a reactive metal and Chlorine is a toxic gas, but Sodium Chloride (table salt) is safe to eat.
- Separation: Constituents can only be separated by chemical or electrochemical reactions, not by physical methods like filtration or magnetic separation.
Common Examples
| Compound | Formula | Constituent Elements |
|---|---|---|
| Water | H2O | Hydrogen, Oxygen |
| Carbon Dioxide | CO2 | Carbon, Oxygen |
| Common Salt | NaCl | Sodium, Chlorine |
| Iron Sulfide | FeS | Iron, Sulfur |
Practice Questions
- Why is air considered a mixture while water is a compound?
- Calculate the ratio by mass of atoms in Carbon Dioxide (C=12, O=16).
- What happens when iron filings and sulfur powder are heated together?
- State one method to separate hydrogen and oxygen from water.
- Is sugar solution a compound or a mixture? Explain.
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