Chemistry Chapters

1. Atomic Structure2. Periodic Classification of Elements3. Chemical Bonding4. Oxidation and Reduction5. Acids Bases Salts6. Behaviour of Gases7. Electrolysis8. Carbon and its Compounds9. Fuels10. Metallurgy11. Important Facts About Some Metals12. Non Metals13. Common Facts

Substance & Its Nature

“Matter is anything that occupies space and has mass. It exists in different forms and can be classified based on its physical and chemical nature.”

What is Matter?

Matter is defined as anything that has mass and occupies space. Everything around us — air, water, metals, and even our bodies — is made up of matter. Matter exists in different physical states and is made up of particles such as atoms and molecules.

Based on physical state, matter can be solid, liquid, or gas. It can also be classified based on composition as pure substances or mixtures.

Classification of Matter

  • Pure Substances: These have a fixed composition and distinct properties. Examples include elements and compounds.
  • Mixtures: These contain two or more substances physically combined and can be separated by physical methods. Mixtures are of two types:
    • Homogeneous Mixture: Uniform composition (e.g., salt water).
    • Heterogeneous Mixture: Non-uniform composition (e.g., sand and iron filings).

Elements, Compounds, and Mixtures

  • Element: A pure substance that cannot be broken down into simpler substances by chemical means. Examples: Hydrogen, Oxygen.
  • Compound: A substance made up of two or more elements chemically combined in a fixed ratio. Examples: Water (H₂O), Carbon dioxide (CO₂).
  • Mixture: Combination of two or more substances that are not chemically combined. Examples: Air, Soil.

Physical and Chemical Changes

Physical Change: A change that affects the physical properties of a substance without changing its chemical identity. Example: Melting of ice, breaking of glass.

Chemical Change: A change that results in the formation of a new substance with different properties. Example: Rusting of iron, burning of paper.

States of Matter

Matter commonly exists in three physical states:

  • Solid: Definite shape and volume. Particles are tightly packed.
  • Liquid: Definite volume but no fixed shape. Particles are loosely packed and can flow.
  • Gas: Neither definite shape nor volume. Particles move freely and are far apart.

Properties of Matter

Physical Properties: These are measurable and observable without changing the substance. Examples: Color, odor, melting point, boiling point, density.

Chemical Properties: These describe the substance’s ability to undergo chemical reactions and form new substances. Examples: Flammability, reactivity with acid.

Previous Year Questions

  • SSC CGL 2019: Which of the following is a pure substance?
  • Oxygen
  • RRB NTPC 2020: Which one is an example of a heterogeneous mixture?
  • Sand and Salt
  • HSSC JE 2017: What type of change is melting of ice?
  • Physical Change
Did You Know? Air is a homogeneous mixture of gases like nitrogen, oxygen, carbon dioxide, and others.

Conclusion

Understanding the nature of substances helps us classify materials around us and predict how they will behave in different conditions. It forms the basis of chemistry and supports various fields such as engineering, biology, and environmental science.

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