Flashcards in C2 Deck (31):
What does melting point mean?
The point at which something melts
What does tensile strength mean?
The force required to break something when stretched
What does compressive strength mean?
The force required to break something when squashed
What is stiffness?
The opposite of flexible; it is the extent to which a material resists deformation on response to a force
What is hardness?
Measure of how resistant a material is to being scratched by another material
What is density?
The amount of mass contained per unit volume.
What three categories can materials come under?
Metal, ceramics and polymers
Give four examples of natural materials obtained from living things
Cotton, paper, silk and wool
What does synthetic mean?
It means humans have made it
Where do the raw materials used to make materials come from?
The Earth's crust
What is crude oil made from?
A mixture of different hydrocarbons of varying chain lenghts
What is a hydrocarbon?
A molecule made from hydrogen and carbon atoms only
A small amount of crude oil is used for chemical synthesis what is the rest used for ?
What is fractional distillation?
A process through which hydrocarbons are heated and separated into fractions of different boiling points in order to produce fuels , lubricants and raw materials for chemical synthesis
How is the size of forces between the hydrocarbon linked to the size of the molecules?
The larger/longer the molecule, the greater the forces between the molecules
Why do larger hydrocarbons have higher boiling points?
It takes more energy to overcome the intermolecular forces between them so that they can break out of a liquid form to form a gas
What is polymerisation?
Monomers join together to make a long molecule called a ploymer
Give an example of material that have replaced other materials because of their properties?
Nylon has replaced silk and cotton in clothing because of its strenght
It is possible to produce a wide range of polymers; why is this a good thing?
It means that different polymers with different properties can be made for particular uses.
What do the properties of a polymer depend upon?
How their molecules are arranged and held together
What feature of a polymer molecule cause varying strength, stiffness, hardness and melting points?
The strength of the forces between the molecules in a polymer (intermolecular forces)
How might increasing the chain of a polymer affect its properties?How does it do this?
Longer polymer chains make a material stronger and less flexible. This is because the polymer chains have stronger forces of attraction between the molecules
How might increasing the cross-linking in a polymer affect its properties?
Cross-links make material tougher and less flexible. This because chemical bonds are used to link together the chains in the polymer
How might using plasticisers in a polymer affect its properties?
Plasticisers make materials softer and more flexible. This is because the small plasticiser molecules are put between the molecule chain and weaken the forces between them. This means less energy is required to overcome the intermolecular forces in the molecule.
How might increasing the crystallinity of a polymer affect its properties and how does it do this?
Crystalline structures are stronger and have higher melting points and density than non-crystalline polymers. This is because in crystalline structures the molecules are lined up regularly giving the material strong intermolecular forces that require lots of energy to seperate
What is the size of nanoparticles?
Name three ways in which nanoparticles can be made?
1. Naturally ie sea salt spray
2.Accidentally ie combustion of fuels
3. Designed in a lab ie silver nanoparticles in wound dressing
Nanoparticles of a material show different properties compare to larger particles of the same material, give one reason for this?
They have a larger surface area to volume ratio
Give two examples of how nanoparticles can be used to modify the properties of materials?
1. Silver antiparticles in fibres have antibacterial properties
2. adding nanoparticles to plastics for sports equipment in order to make them stronger
Why is there concern about the use of nanoparticles?
The effects of nanoparticles are not yet known but they may have some negative effects on human health