1. Chapter 5: Classification of Matter fibre Observe the things around you, are you able to identify the different types of matter? wood plastic

5. 5.2 Physical Properties of Materials Materials Matter that is used for making objects Chosen to make objects based on their physical properties Physical property Any aspect of an object that can be measured without changing its identity Includes density, strength, hardness, flexibility, electrical conductivity, thermal conductivity, melting and boiling point Why are different materials used to make cups? glass paper ceramic

9. Thermal Conductivity Thermal conductivity = measure of how readily heat flows through the material Thermal conductors Thermal insulators Allow heat to flow through them easily (e.g. metal) Do not allow heat to flow through them easily (e.g. non-metals & gases) Example : Almost every part of the kettle is made of stainless steel except for the handle (plastic) because we want heat to be transmitted through the metal quickly to boil water, and the handle to be cool so that we can hold the kettle. Can you think of other examples? metal plastic

11. 5.3 Distinguishing Between the Main Classes of Materials To reduce the amount of materials disposed we need to first understand the properties of different materials. Scientists have classified materials into five main classes: metal plastic glass ceramic fibre

12. Material Good conductor of heat? Good conductor of electricity? NO YES Can be spun into thread and woven into cloths? YES fibre NO Brittle? YES Opaque? NO NO YES Can be moulded into different shapes after melting? YES plastic glass High melting point? ceramic YES Shiny surfaces? YES High melting and boiling points? Malleable and ductile? YES metal YES YES

14. 5.4 Choosing the Right Materials Why are different materials chosen for different parts of the bulb? Bulb Function : give off light Material : glass Properties : transparent, electrical insulator Filament Function : produce light when heated Material : tungsten Properties : electrical conductor, high melting point, ductile, malleable Connecting and supporting wires Function : provide support to filament Material : Tungsten Properties : Electrical conductor, high melting point, ductile, malleable Exhaust tube Function : provide support to filament and connecting wires Material : Ceramic Properties : electrical insulator, high melting point, heat insulator, strong Base Function : connect bulb to power source Material : metal Properties : Electrical conductor, malleable