C2 - Material Choices Flashcards
How big is a nanometre?
1.0-9 of a metre or 1.0-6 mm
How is a crystalline polymer different?
Its chains are closely packaged together.
Why must you keep all factors except one variable factor constant in an experiment?
- To keep it a fair test.
- Another factor could influence the result.
- The factor will not be the only one that can affect the outcome/no longer able to compare results.
Discuss the risks of using plasticisers, and why people may view these risks differently.
Risks
- Harm young children, who may use materials which contain plasticisers in toys.
- Our bodies do not decompose them/they accumulate in tissue.
- Plasticisers could leach out of PVC and into food, the environment or human tissue.
- Plasticisers known to cause harm to rats.
Views
- Evidence linking them with cancer. Some argue that they have been used for over half a century and no known cases of harm are known.
- Insufficient evidence/no causal mechanism.
- Biased views from plastic manufacturers/public pressure groups.
- Plasticiser concentrations in humans/environment are very low/below EU limits.
- Some people may perceive the risk higher than it actually is.
- Some people may think the benefit outweighs the risk, but others think the opposite.
- Data on harmful effects is inconclusive.
- Data from animals may not indicate what is true for humans.
- Using plasticisers has benefits with examples.
- Most people do not know enough to be worried.
- Manufacturers/scientists have vested interests.
Why do we use rock salt to treat icy roads?
It melts the ice by lowering the melting point.
Why do we not use rock salt in the food industry?
It may contain impurities.
Describe how salt is obtained by solution mining.
Water is pumped underground and into the salt deposit.
Salt dissolves in the water, forming a concentrated salt solution.
Then, this is pumped up to the surface ready for use.
Discuss the environmental issues that can occur as a result of solution mining.
There are gaps underground where the salt was removed. Also, subsidence can occur, causing buildings to sink/sink holes to appear.
Give a natural example of where nanoscale particles are used.
In sea spray.
Give an accidental example of where nanoscale particles are used.
During the combustion of fuels, particulate carbon can be released.
What is it called when nanoscale particles are made deliberately by scientists?
Nanotechnology.
Define melting point.
The temperature at which a solid turns into a liquid.
Define tensile strength.
The force needed to break a material when it is being stretched.
Define compressive strength.
The force needed to crush a material when it is being squeezed.
Define stiffness.
The force needed to bend a material.
Define hardness.
How well a material stands up to wear. Can be compared by scartching two materials together.
Define density.
The mass of a given volume of material. Compares how heavy something is for its size.
Give reasons why synthetic materials have replaced natural materials.
- Some natural materials are in short supply.
- They can be designed to give particular properties.
- They are often cheaper and can be made in the quantity needed.
What are most hydrocarbons used for?
Fuels (90%).
Compare LDPE and HDPE.
LDPE has long chains with branches.
HDPE has long chains but no branches. It is more crystalline, but can be brittle.
Thermoplastics can/can not be heated and moulded into shape.
Thermoplastics can be heated and moulded into shape.
Thermosetting plastics can not. They contain cross-links.
How are crystalline structures manufactured?
By removing branches on the main polymer chain and making the chains as flat as possible.
Then, the polymers are drawn through a tiny hole when heated, to make the chains line up and set close together, forming a higher tensile strength fibre.
Discuss the benefits and risks of using nanoparticles.
Benefits
- They can kill bacteria (Silver nanoparticles).
- Nanoparticles occur naturally, and pose no danger.
Risks
- Silver nanoparticles can be washed out of clothes and into the environment, killing useful bacteria (e.g: In sewers) or microorganisms in the environment.
- Nanoparticles are small enough to pass through skin into blood, and into body organs. The possible medical effects of this are not yet known.
- Little research has been carried out onto the harmful effects of nanoparticles.
- A fear is that nanoparticles in the air might be breathed in and cause lung or brain damage.
- New nanoparticles with new properties have been manufactured.
- No one knows if nanoparticles used in solids can escape into the air.
- Some people want proof.
What are the units of density?
g/cm3 or kg/m3.
