Physical properties are inherent characteristics of a material that can be observed or measured without applying external forces. These properties describe the material itself, regardless of how it will behave under stress. Physical properties commonly considered in design are weight, mass, volume, density, electrical resistivity, thermal conductivity, thermal expansion and hardness.

• Mass: The amount of matter an object contains, constant regardless of location (measured in kilograms, kg).

• Weight: The force exerted on an object due to gravity (depends on location, measured in Newtons, N). Think of weight as the heaviness you feel.

• Volume: The amount of space an object occupies (measured in cubic meters, m³).

• Density: How much mass is packed into a unit volume (mass per unit volume, kg/m³). High density means more mass in a smaller space. Opposite: Friability.

• Electrical resistivity: How strongly a material opposes electric current (measured in ohm-meters, Ω⋅m). High resistivity means a material is a good insulator. Low resistivity means a material is a good conductor. 

• Thermal conductivity: How well a material conducts heat (measured in watts per meter-kelvin, W/(m⋅K)). High conductivity means heat flows easily.

• Thermal expansion: How much a material's dimensions change with temperature (usually a unitless ratio). Higher expansion means it grows more when heated.

• Hardness: A material's resistance to permanent indentation (various scales like Rockwell, Vickers or Mohs). Harder materials scratch softer ones more easily. Opposite: softness.

Mechanical properties tell you how a material responds to external forces. They describe the material's behaviour under stress or strain. Mechanical properties commonly considered in design are tensile strength, compressive strength, stiffness, toughness, hardness, ductility, elasticity, plasticity and Young’s modulus. Think of it this way: physical properties are like a material's identity card, while mechanical properties are like its report card on how it performs under pressure.

• Strength: More specifically tensile strength, compressive strength, shear strength, yield strength or breaking strength. Strength is a general term describing the ability of a material to withstand stress without breaking. 

• Tensile strength: The maximum stress a material can withstand before pulling apart. High tensile strength is crucial for suspension cables in bridges and elevators, which need to bear weight without snapping.

• Compressive strength: The maximum stress a material can withstand before crushing. Concrete has excellent compressive strength, making it ideal for building foundations that support massive structures.

• Stiffness: Resistance to elastic deformation under load. It describes how much a material bends before breaking. I-beams used in buildings are designed with high stiffness to minimize bending under heavy loads placed on floors.

• Ductility: The ability to deform plastically under tension without breaking (drawability as opposed to brittleness. Imagine stretching a wire. Copper wires are ductile, allowing them to be drawn into thin wires for electrical applications.

• Toughness: The ability of a material to absorb energy before fracturing (impact resistance or fracture resistance as opposed to brittleness). It combines both strength and ductility. Steel is a tough material because it can withstand a significant impact without breaking, making it suitable for car frames. 

• Elasticity: Ability of a material to return to its original shape after deformation (resilience or springiness as opposed to plasticity). Think of a rubber band snapping back. Springs rely on elasticity to store and release energy, using their ability to return to their original shape. Pole-vaulting poles need to flex when a force is applied to it in order to propel the athlete over the bar. 

• Plasticity: The ability of a material to deform permanently under stress, without breaking (yielding as opposed to elasticity). Imagine bending clay to a new shape. Aluminum is a good example of a plastic material. It can be bent and moulded into different shapes without breaking.

• Malleability: Ability of a material to be hammered or pressed into thin sheets without breaking (pliability as opposed to brittleness ).

• Fatigue Strength or endurance limit: Maximum stress a material can withstand for a specific number of loading cycles without failure.

• Creep: Tendency of a material to deform slowly under a constant load over time.

• Abrasion resistance: Ability of a material to resist wear and tear from friction.

• Young's Modulus: A measure of stiffness that relates stress to strain in the elastic region. A higher Young's Modulus indicates a stiffer material. Piano wires require a high Young's Modulus to maintain their tight tension and vibrate at precise frequencies when struck, producing clear musical notes.

Aesthetic properties of materials aren't as clearly defined as physical or mechanical properties. They deal with how a material appeals to our senses, and perception can be subjective. However, some common characteristics contribute to a material's aesthetic appeal:

• Visual (appearance): This includes properties like colour, gloss, transparency, and pattern. These properties can be influenced by factors like:

• Surface finish: Polishing, sanding, or etching can alter a material's visual and tactile qualities.

• Light interaction: How a material reflects, absorbs, or transmits light can affect its perceived colour and texture.

• Tactile (texture): How a material feels to the touch, such as smooth, rough, soft, hard, cool, or warm.

• Auditory: Some materials have unique sounds associated with them, like the crackle of wood burning or the clink of glass.

While taste and smell are technically senses involved with materials, they're often associated with consumption rather than inherent material properties. 

Mixing materials with different aesthetic properties can create interesting contrasts or complements.