Sha Tin CollegeTopic 4 MaterialsStudent responses to research into properties

of materials

Roseda

Phoebe

Helene

What is density?How heavy something is compared to its sizeMeasured in kg/m–3 Mass (M) per unit volume (V)= M / V

When is density important?Material used for constructionMust be strong and light :Bridges - strongBoats – buoyant Planes – light

Sam Inglis, Raymond Chan, Alan Tsang

Definition: A measure of how well a material can conduct electricity. Materials with a low resistivity have a high level of conduction.

Wikipedia Definition: Electrical resistivity (also known as specific electrical resistance) is a measure of how strongly a material opposes the flow of electrical current. A low resistivity indicates a material that readily allows the movement of electrical charge. The Sl unit of electrical resistivity is the ohm metre.

UsesTo protect electrical appliances; resistorsTo protect ourselves; lightning rodsLow resistivity to transfer electricity over

long distances

Конец Сэм, Раймонд, Алан

Jacqueline Leung, Angel Chau, Teresa Lam

Definition of Thermal Conductivity

Thermal conductivity is the intensive property of a material that indicates its ability to conduct heat

Physical Properties

High thermal specific heat capacityConducts heat

Metal Examples

AluminiumBrassCopperPewter

Design ContextsIronHeaterOvenKettleSaucepanRice cooker

Thermal Expansion

Thermal Expansion

Hardness Hardness refers to various properties of matter in the solid

phase that give it high resistance to various kinds of shape change when force is applied.

Allows stability and balances weight?

Types of hardness:

Scratch Hardness: Resistance to fracture or plastic (permanent) deformation due to friction from a sharp object

Rebound Hardness: Height of the bounce of an object dropped on that material, related to elasticity.

How they are important in situation Scratch hardness is usually used when penetrating softer

materials for e.g. a drill – the drill bit is much harder than the material it is penetrating

Pure diamond is the hardest known natural mineral substance to man

It will penetrate any other natural material. Diamond is therefore used to cut other diamonds for e.g. higher-

grade diamonds are used to cut lower-grade diamonds.

By: Kim Choy, Dongwan Roh,

Kevin Mak

Definition

Tensile strength is a measure the amount of stress that it can be subjected before failure.

(source from wikipedia)

Basic Facts

Different materials have different tensile strengths, e.g. Lead has the ultimate strength of 12MPa.

The peak stress level is known as the ultimate tensile strengths

Graph1 Ultimate Strength 2 Yield Strength

(level of stress which causes deformation)

3 Proportional Limit Stress

4 Rupture (breaking)

5 Offset Strain (usually 0.002)

Stiffness is the resistance of an elastic body to deflection or deformation by an applied force (the physical property of being inflexible and hard to bend).

Situations – Race Cars, Boats, Aircrafts, Engineering

Used for improving the handling performance of boats, cycles, aircraft, skis and other leisure items of transport. Stiffness can also improve crash resistance, which can be demonstrated by racing cars.

By Chun Tung, Celeste Tse, Anisha Sindhergoobbeldegook

DEFINITIONThe ability of a material to deform plastically

and to absorb energy in the process before fracture

The amount of force required to deform a material by 1 cubic inch.

USESBullet proof vestsCablesKitchenware; pans, sinks.Structural SkeletonsArchitectureWallsAnything requiring non-conforming rigidity

propertiesDuctility is the mechanical property of being

capable of sustaining large plastic deformations due to tensile stress without fracture such as in metals, such as being drawn into a wire

Areas in which ductility is put into consideration Alloys used for gas turbo engines rocket

propulsion systems, and space power systems Composition used for lamination To make non ferrous metal.