C2 - Material Choices

Natural and Synthetic Materials

• We use a wide range of materials, including metals, ceramics and polymers.
• All are made of chemicals, either individual chemicals or mixtures of chemicals.
• Chemicals are made up of atoms/groups of atoms bonded together.
• Some materials are mixtures = different substances not chemically bonded together.
• Synthetic means man made materials.

Different materials have different properties

Different properties -

• Melting points (temperature solid truns to liquid).
• Strength (how good at resisting force) ---> tension (resist pulling) and compressive (resist push).
• Stiffness (not bending when force applied).
• Hardness (difficulty of cutting it).
• Density (mass per unit volume).

Materials, properties and uses

Possible uses for material depend on its properties - e.g. plastics, fairly hard, strong and stiff with a low density.

The effectiveness of a product is how good it it at the job it's meant to do. A products effectiveness depends on the materials it's made from. Materials also effect a product's durability - how long it will last.

By looking at properties, we can decipher whether it is suitable for its purpose.

Crude oil and its uses

Crude oil a mixture of hydrocarbons. Hydrocarbons are molecules made of carbon and hydrogen atom chains.

As length of carbon chain changes, the properties of the hydrocarbon change. Short-chain = lower boiling points. Long chains = high boiling points.

Two types of bond in crude oil = 

• Strong covalent bonds between carbons and hydrogens within each hydrocarbon molecule.
• Intermolecular forces of attraction between different hydrocarbon molecules in the mixture.
• Crude oil is heated - molecules have more energy.
• Molecules move more, overcome intermolecular forces.

Covalent bonds are much stronger than the foces, so bonds don't break. Forces break easier in small molecules.

The process of seperating…