Topic 4.1 - Properties of Materials

Physical Properties

• Mass
  • Measurement of amount of matter in a material.
  • Units - grams (g), kilograms (kg)
• Weight
  • Measurement of the force gravity exerts on a material.
  • Units - Newtons (N)
• Volume
  • Measurement of the amount of 3-dimensional space an object takes up.
  • Units - cubic centimeters (cm3), cubic meters (m3), milliliters (ml), liters (l)
• Density
  • Measurement of the mass per unit of volume.
  • Units - kg/m3, g/cm3
• Electrical Resistivity
  • Measures the ability of a material to resist the flow of electricity. A material of low resistivity conducts electricity well.
  • Units - Ohms (Ω)
  • Electricical Conductivity is the reciprocal of resistivity, so is the ability of a material to conduct electricity.
  • Units - Siemens (S),
• Thermal Conductivity
  • Measures how well heat travels through a material.
  • Units - watts per meter-kelvin (W/(m⋅K))
• Thermal Expansion
  • Measures the degree to which a material increases in volume (or decreases in density) when it is heated.
  • Units - coefficient of thermal expansion (CTE)
• Hardness
  • Measures the resistance of material to scratching or indentation.
  • Units - Mohs scale of mineral hardness (qualitative ordinal scale from 1 to 10)

Mechanical Properties

• Tensile strength
  • Measures the ability of a meterial to resist pulling forces.
• Compressive strength
  • Measures the ability of a meterial to resist pushing forces.
• Stiffness
  • Measures the ability of a material to resist changing shape when a force is applied to it.
• Toughness
  • Measures the ability of a material to change shape without breaking when a force is applied to it.
  • The opposite of tough is brittle.
• Ductility
  • Measures the ability of a material to be drawn, stretched, or extruded into a wire-like form.
  • Malleability is a similar property but not the same, as it is about the ability of a material to be deformed through compression (eg. hammering)
• Elasticity
  • Measures the ability of a material to deform then return to its original shape when a force is applied.
• Plasticity
  • Measures the ability of a material to undergo a permanent change in shape when a force is applied.
• Stress & strain
  • Stress is the tensile force applied to a given area (N/m2).
  • Strain is the percentage change in length when a force is applied (change in length/original length)
• Young’s Modulus
  • Measures the stiffness of an object by quantifying the relationship between stress and strain.