SC26 - Bulk and Surface Properties of Matter Including Nanoparticles

A range of durable compounds that change very little when heated

• Chemically unreactive hard and stiff brittle • Poor electrical and thermal conductors • High melting points These properties are due to their giant ionic/covalent structures with strong bonds

• Bricks • Porcelain • China

• When clay is heated to high temperatures, tiny crystals form and join together. • Bricks are decorated by adding a coloured substance before heating, or by moulding in patterns. • Porcelain and china are dipped into a ‘glaze’ and heated strongly. • This makes them hard, waterproof and smooth.

Melting sand and then allowing it to cool and then solidify

• They both have similar properties because they both have giant structures • But, the atoms in glass aren’t arranged in a regular pattern to form crystals and so glass is transparent rather than opaque

The float process: • Molten glass is poured onto a bath of molten tin. • As it spreads out, it is drawn away and cooled in a continuous process

Polymers are substances with high relative formula masses as they are formed by joining many monomers (smaller molecules) together

Properties depend on structure and chemical composition, but generally: • Can be moulded into complex shapes • Strong • Chemically unreactive • Poor electrical and thermal conductors

By using plasticisers in its manufacturing. This makes it more flexible

• Strong • Hard • Shiny • High melting points • Good electrical and thermal conductors • Malleable

Alloying: Mixing the metal with one or more other elements

• To improve resistance to corrosion • To improve appearance

A material that is made up of two or more materials, combined to make a material with improved properties

• They often have contrasting properties • They can be separated out by physical means

• The reinforcement is what you are binding together • The matrix is how you hold them together (reinforcement is straw and matrix is the glue)

• Tensile: Resistance when stretched • Compressive: Resistance when squashed

Cellulose fibres in a matrix of a polymer called lignin

It is stronger along the grains (parallel to lines of lignin) than across the grain (perpendicular to lines of lignin)

It has an odd number of sheets of wood glued in right angles to the sheet below so that you are always cutting across and along the grain simultaneously

Reinforcement of ice in a matrix of wood pulp

Reinforcement of sand and aggregate (small stones/gravel) in a matrix of cement (and water to help it set)

• Reinforcement of thin glass in a matrix of resin polymer. • Glass fibres are brittle but with low density and high tensile strength • Resin is hardwearing but not strong. • Combining them makes fibreglass low density, strong and hardwearing

• Concrete has a low tensile strength but high compressive strength • Steel is very dense and more expensive than concrete • Reinforced with steel it will have high tensile and compressive strength and also be cheaper and less dense than steel alone