Elements, Compounds, and Mixtures | Class 8 Science Notes
By ConceptScroll Team · Published on 17 July 2026 · 4 min read
Elements, Compounds, and Mixtures – this guide gives you a concise, exam-ready overview of Elements, Compounds, and Mixtures from Class 8 Science, written by ConceptScroll editors and reviewed against the latest NCERT textbook.
8.5 What Are Minerals?
Minerals are naturally occurring solid substances found in the Earth's crust with fixed chemical compositions. Most rocks are mixtures of minerals. Minerals can be native, consisting of pure elements like gold, silver, and copper, or compounds like quartz, calcite, mica, pyroxene, and olivine. Minerals are important sources of metals and other materials used in daily life and industry. For example, cement is made from minerals like calcite and quartz, and talcum powder is made from the mineral talc. Understanding minerals helps in extracting useful elements and compounds for various applications. The ancient Indian craft of Dhokra art uses alloys like brass and bronze to create artistic metal figures, demonstrating the use of mixtures in cultural heritage.
📊 Diagram: Figures 8.22 show images of minerals quartz, calcite, mica, pyroxene, olivine, and talc; Figure 8.23 depicts Dhokra art figures made from metal alloys.
🔗 Connection: Summarizes concepts and prepares for review questions and activities.
Frequently asked questions
Consider the following reaction where two substances, A and B, combine to form a product C: $$ \mathrm {A} + \mathrm {B} \longrightarrow \mathrm {C} $$ Assume that A and B cannot be broken down into simpler substances by chemical reactions. Based on this information, which of the following statements is correct? (i) A, B, and C are all compounds and only C has a fixed composition. (ii) C is a compound, and A and B have a fixed composition. (iii) A and B are compounds, and C has a fixed composition. (iv) A and B are elements, C is a compound, and has a fixed composition.
Option (iv) is correct: A and B are elements, C is a compound, and has a fixed composition.
Explanation: Since A and B cannot be broken down into simpler substances by chemical reactions, they are elements. When they combine chemically, they form a compound C which has a fixed composition. Compounds have properties different from their constituent elements and a fixed ratio of elements.
Assertion: Air is a mixture. Reason: A mixture is formed when two or more substances are mixed, without undergoing any chemical change. Choose the correct option: (i) Both Assertion and Reason are true and Reason is the correct explanation for Assertion. (ii) Both Assertion and Reason are true, but Reason is not the correct explanation for Assertion. (iii) Assertion is true, but Reason is false. (iv) Assertion is false, but Reason is true.
Option (i) is correct.
Explanation: Air is a mixture because it consists of several gases mixed physically without any chemical change. The reason correctly explains the assertion that a mixture is formed when substances are mixed without chemical change.
Water, a compound, has different properties compared to those of the elements oxygen and hydrogen from which it is formed. Justify this statement.
Water is a compound formed by chemical combination of hydrogen and oxygen in a fixed ratio (2:1). The properties of water are very different from those of hydrogen (a flammable gas) and oxygen (supports combustion). Water is a liquid at room temperature, does not support combustion, and has unique properties like high boiling point and surface tension. This difference arises because compounds have properties different from their constituent elements due to chemical bonding and new molecular stru
In which of the following cases are all the examples correctly matched? Give reasons in support of your answers. (i) Elements — water, nitrogen, iron, air. (ii) Uniform mixtures—minerals, seawater, bronze, air. (iii) Pure substances—carbon dioxide, iron, oxygen, sugar. (iv) Non-uniform mixtures — air, sand, brass, muddy water.
Correct matches: (ii) Uniform mixtures—seawater, bronze, air are correctly matched because these are homogeneous mixtures. (iii) Pure substances—carbon dioxide, iron, oxygen, sugar are correctly matched as these are pure substances (elements or compounds).
Incorrect matches: (i) Elements — water and air are not elements; water is a compound and air is a mixture. (iv) Non-uniform mixtures — air and brass are not non-uniform mixtures; air and brass are uniform mixtures.
Explanation:
- Elements a
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Clear NCERT-aligned notes on LIGHT for Class 8 Science.
- LIGHT | Class 8 Science Notes
Clear NCERT-aligned notes on LIGHT for Class 8 Science.