Chapter => 4 (Materials: Metals & Non-Metals) Of Class 8 Definitions

These are Definitions of Chapter =>4 (Materials: Metals & Non-Metals) Of Class 8, Learn And Practice For CBSE Examinations.

Definitions: 

1.   Metals=> A solid material which is typically hard, shiny, malleable, fusible, and ductile, with good     electrical and thermal conductivity (e.g. iron, gold, silver, and aluminium, and alloys such as steel).

2. Non-Metals=> They are not sonorous and are poor conductors of heat and electricity. These                materials are called non-metal.

3. Sonorous => Since metals produce ringing sounds, they are said to be sonorous .The   material           other than metals are not sonorous.

4. Malleability=> The property of metals by which they can be beaten into thin sheets is called               malleability.

5.  Ductility=> The property of metal by which it can be drawn into wires is called ductility.

6.  Conductor=> A conductor is a material which permits a flow of energy.

7. Good Conductor=> A material through which electric current can pass. In general, metals are good       conductors. Copper or aluminum is normally used to conduct electricity in commercial and                 household systems.

8.  Poor Conductor=> Poor conductors have a low density thus the particles in a given volume of the         material are not enough to collide and transfer heat. Examples of poor heat conductors include air,       wood, paper, cloth and water.

9. Electrical Conductor=> A material which allows the flow of charged particles is an electrical               conductor. 

10. Thermal Conductor=> A material which allows the transfer of thermal energy is a thermal                   conductor or heat conductor.

11. Magnesium Ribbon=> A light, silvery-white, moderately hard metallic element that in ribbon or           powder form burns with a brilliant white flame. Obtained chiefly from magnesite, dolomite, and         bodies of salt water, it is used in structural alloys, pyrotechnics, flash photography, and incendiary       bombs.

12. Phosphorus=> It 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.

13.Sodium Metal=> It is a very reactive metal. It reacts vigorously with oxygen and water. A lot of           heat is generated in the reaction. It is, therefore, store in kerosene.

14. Mercury=> Mercury is the only metal which is found in liquid state at room temperature. These           are exceptions.

15. Displacement Reaction=> Displacement reaction is a chemical reaction in which a more reactive           element displaces a less reactive element from its compound. Both metals and non-metals take           part in displacement reactions. Example  : Reaction of iron nails with copper sulphate solution.

16.   Atom=> The smallest particle of a chemical element that can exist.

17. Elements=> An essential or characteristic part of something abstract.

 18. Hardness=> Hardness is a measure of how resistant solid matter is to various kinds of permanent       shape change when a compressive force is applied.

19. Metalloids => A metalloid is any chemical element which has properties in between those      of metals and nonmetals, or that has a mixture. of them.