Sec 2 Unit 01: Classes and Properties of Materials

• Physical properties classify objects via observable or measurable characteristics.

Physical Properties

• Hardness, mass, and density serve as examples of physical properties.

Melting Point

• Melting point refers to the temperature at which a substance transitions from a solid to a liquid state.
• Copper's high melting point is 1084°C.
• Polyethylene plastic has a low melting point of 110°C.

Boiling Point

• Boiling point denotes the temperature at which a substance transitions from a liquid to a gaseous state.
• Mercury's high boiling point is 365°C.
• Alcohol has a low boiling point of 78°C.

Density

• Density is the mass per unit volume of a substance.
• Metals commonly exhibit high density.
• Wood typically has low density.

Strength

• Strength is a material's capacity to endure a heavy load without sustaining damage.
• Iron is considered to have good strength.
• Glass has poor strength.

Hardness

• Hardness is a material's capacity to resist wear and scratches, and is measured on the Mohs scale from 1-10.
• Diamond is considered to be very hard.
• Talc is considered to be not very hard.

Flexibility

• Flexibility is a material’s capacity to bend without breaking and return to its original shape.
• Rubber demonstrates good flexibility.
• Glass has poor flexibility.

Malleability

• Malleability is a material’s capacity to be hammered or beaten into different shapes without breaking, and is typically used to describe metals.
• Pure gold is very malleable.
• Cast iron is not very malleable.

Ductility

• Ductility refers to a material’s capacity to be stretched into wires.
• Copper has good ductility.
• Ceramic has poor ductility.

Electrical Conductivity

• Electrical conductivity measures how readily electric current passes through a substance.
• Iron has good electrical conductivity.
• Plastic has poor electrical conductivity.

Classes of Materials

• Materials are substances used to create objects.
• Materials are classified into 5 main classes.

Metal

• Metals are extracted from the ground.
• Metals are shiny, good conductors of heat and electricity, malleable, and ductile.
• Some metals corrode easily, while others do not.

Glass

• Glass is made from sand.
• Glass is transparent and brittle.
• Glass is a poor conductor of heat and electricity that does not corrode, but can be moulded into shapes.

Ceramic

• Ceramics are non-metallic solids made from clay.
• Ceramics are hard but brittle with a high melting point.
• Ceramics are poor conductors of heat and electricity that do not corrode.

Plastic

• Plastics are made from petroleum.
• Plastics are strong but light, with low density.
• Plastics do not corrode easily, are poor conductors of heat and electricity and can be moulded into shapes.

Fibre

• Fibres can be manmade or natural.
• Fibres can be spun into threads and woven into fabrics, and can absorb dyes.

Alloys

• An alloy is a mixture of two or more elements, with at least one being a metal.
• Alloys are created to increase strength or resistance to corrosion.
• Alloys consist of atoms in a foreign element that disrupt the orderly arrangement of atoms, making it difficult for layers of atoms to slide over each other when force is applied.

Amalgam

• Amalgam is an alloy made of 50% mercury, 25% silver, 14% tin, 8% copper, and trace amounts of indium and palladium.
• Amalgam is used for dental fillings.

Brass

• Brass is an alloy composed of 65% copper and 35% zinc.
• Brass is used for jewelry and machine bearings.

Bronze

• Bronze is an alloy made up of 90% copper and 10% tin.
• Bronze is used for machine parts.

Duralumin

• Duralumin is an alloy containing 95% aluminum, 4% copper, and 1% magnesium, manganese, and iron.
• Duralumin is used in aircraft construction and bicycle parts.

Hard Steel

• Hard steel is an alloy containing 99% iron and 1% carbon.
• Hard steel is used for cutting tools.

Composites

• A composite combines two different materials to create a new substance with enhanced or specialized properties.
• Composites consist of a matrix and a reinforcement.

Glass-Reinforced Plastic (GRP)

• Glass-reinforced plastic (GRP) is a composite of glass and plastic.
• Glass is corrosion resistant.
• Plastic is strong, and light and can be moulded into shapes.
• GRP does not break when bent or moulded, can withstand force from collisions, and is lightweight.