Physical and Chemical Properties

Physical properties are those that can be observed without changing the identity of the substance. The general properties of matter such as color, density, hardness, are examples of physical properties. Properties that describe how a substance changes into a completely different substance are called chemical properties. Flammability and corrosion/oxidation resistance are examples of chemical properties.

The difference between a physical and chemical property is straightforward until the phase of the material is considered. When a material changes from a solid to a liquid to a vapor it seems like them become a difference substance. However, when a material melts, solidifies, vaporizes, condenses or sublimes, only the state of the substance changes. Consider ice, liquid water, and water vapor, they are all simply H2O. Phase is a physical property of matter and matter can exist in four phases – solid, liquid, gas and plasma.

Some of the more important physical and chemical properties from an engineering material standpoint will be discussed in the following sections.

  • Phase Transformation Temperatures
  • Density
  • Specific Gravity
  • Thermal Conductivity
  • Linear Coefficient of Thermal Expansion
  • Electrical Conductivity and Resistivity
  • Magnetic Permeability
  • Corrosion Resistance