Physical Properties of Materials
Definition
Physical Properties
Physical properties are characteristics that can be observed or measured without altering the material's chemical composition.
- Physical properties are intrinsic to the material and remain constant regardless of the sample size or shape.
- They tend to be the characteristics of materials that can be identified through non-destructive testing.
- The key physical properties include:
- Density
- Thermal Conductivity
- Thermal Expansion
- Melting Point
- Electrical Resistivity
- Electrical Conductivity
Density
Definition
Density
The mass per unit volume of a material (usually measured in kg/m³ or g/cm³). Its a measure of mass divided by volume (ρ = m/V)
Significance:
- Weight Considerations: High-density materials like steel are used in structures requiring strength, while low-density materials like aluminum are preferred in aerospace for weight reduction.
- Buoyancy: Density determines whether an object will float or sink in a fluid.
Aluminium's low density makes it an ideal material for an aircraft.
Thermal Conductivity
Definition
Thermal Conductivity
A measure of how quickly heat passes through a material when there is a temperature difference across it. It is measured in watts per metre per degree Celsius (W/m·°C).
- Think of thermal conductivity like a highway for heat.
- A high-conductivity material is like a wide, fast highway, allowing heat to travel quickly, while a low-conductivity material is like a narrow, slow road, restricting heat flow.
Significance:
- Insulation: Materials with low thermal conductivity, like fiberglass, are used as insulators.
- Heat Dissipation: High thermal conductivity materials, such as copper, are used in heat sinks to dissipate heat in electronics.
- Cookware: Needs materials with high thermal conductivity to heat food evenly.
- Building insulation: Uses materials with low thermal conductivity to keep heat in or out.
