04 – Materials : Metals and Non-metals | Science | NCERT | Class 8

Here a student can find important notes in a listed form for quick study and revision. The blog includes the important definitions and terminologies from the Chapter 04 : Materials : Metals and Non-metals, from NCERT Science, of Class 8.

1. Metals can be distinguished from non-metals on the basis of their physical and chemical properties.

2. Malleability : The property of metals by which they can be beaten into thin sheets
is called malleability.

3. Ductility : The property of metal by which it can be drawn into wires is called ductility.

4. Metals produce ringing sounds, and they are said to be sonorous.

5. General properties of metals: hard, lustrous, malleable, ductile, sonorous and good conductors of heat and electricity.
E.g.: iron, copper, aluminium, calcium, magnesium, etc.

6. Non-metals: Materials like coal and sulphur that are soft and dull in appearance, break down into a powdery mass on tapping with a hammer, are not sonorous, are poor conductors of heat and electricity, are called non-metals.
E.g.: sulphur, carbon, oxygen, phosphorus, etc.

7. Some exceptions of metals:
– Metals like sodium and potassium are soft and can be cut with a knife.

– Mercury is the only metal which is found in liquid state at room temperature.

8. In general, metallic oxides are basic in nature.

9. Generally, oxides of non-metals are acidic in nature.

10. Sodium metal is very reactive. It reacts vigorously with oxygen and water. A lot of
heat is generated in the reaction. It is, therefore, stored in kerosene.

11. Phosphorus is a very reactive non-metal. It catches fire if exposed to air. To prevent
the contact of phosphorus with atmospheric oxygen, it is stored in water.

12. Non-metals generally do not react with acids but metals react with acids and produce
hydrogen gas that burns with a pop sound.

13. The pop sound indicates the presence of hydrogen gas.

14. Copper does not react with dilute hydrochloric acid even on heating but it reacts with sulphuric acid.

15. Metals react with sodium hydroxide to produce hydrogen gas.

16. Reactions of non-metals with bases are complex.

17. One metal displaces another metal from its compound in aqueous solution.

18. Decreasing order of reactivity of metals with water and dilute acids:
potassium > sodium > lithium > calcium > magnesium > zinc > iron > copper.

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