What are the materials from animals?
- Wool comes from sheep
- Silk is made by the silkworm larva.
- Leather is made from cows.
What are synthetic materials?
Man made materials are called “synthetics”.
- All rubber used to come from the sap of the rubber tree. We still get a lot of rubber this way. However, you can make rubber in a factory.
- Making things in a factory has an advantage because you can control its properties making it suitable for different purposes.
- Clothes are made from Nylon and Polyester- they are man made fabrics.
- The properties of synthetic fabrics can be controlled by the manufacturer. (Water proof,glittery)
- Paints are a mixture of man made chemicals. The pigment and the stuff that holds it together are tough to stop the colour fading.
- Raw materials used to make synthetic materials comes from the Earths crust.
Melting point?
Most materials that are pure chemicals have a unique melting point. This is where the solid turns to a liquid.
Strength?
Strength is how good a material is at resisting a force.
You can indicate how strong a material is by how much force is needed to break or deform it.
What are the 2 types of strengths?
Tensile (or tension) strength- how much a material can resist a pulling force.
For example, a rope has to have high tensile strength or it’d snap.
Compressive strength- how much a material can resist a pushing force.
For example, bricks need good compressive strength or they would get squashed by the weight of the bricks above them.
Stiffness?
A stiff material is good at not bending when force is applied to it.
Materials like steel are difficult to bend.
Rubbers are strong and can bend and stretch and they are not stiff.
Hardness?
The hardness of a material is how difficult it is to cut into it.
The hardest natural materials are diamonds. A diamond can only cut another diamond.
Density?
Density is a materials mass per unit volume.
For example,
Air is not very dense. You need a huge volume of it to make 1kg in mass.
Gold is very dense. A small volume of gold would make up 1kg in mass.
Advantages of plastics?
- Can be hard,strong and stiff.
- Low density (lightweight)
- Mouldable
e.g. Cases for TVs, computers and kettles.
Advantages of rubber?
- Strong but soft and flexible
- Mouldable
E.g. Rubber car tyres.
Advantages of nylon fibres?
- Soft and flexible
- Good tensile strength
E.g. Ropes and clothing fabric.
What does a products effectiveness mean??
The effectiveness of a product is how good it is at the job it’s supposed to do.
What does a products durability mean??
Materials also affect a products durability- how long it will last.
Suitability of materials?
- Cooking utensils must be made from something with a high melting point that’s non toxic.
- A toy car must be made from a material that’s non toxic,strong,stiff and low density.
- Clothing fabric can’t be stiff, made of good tensile strength and high flame resistance.
What is crude oil?
Crude oil is a mixture of hydrocarbons.
Hydrocarbons are molecules that are made of chains of carbon and hydrogen atoms only.
The chains are of varying lengths.
How do hydrocarbon properties change?
- Short chain molecules have lower boiling points- they are often gases.
- Long chain molecules have high boiling points and can be viscous (thick and sticky)
What are the 2 types of bond in crude oil?
Strong covalent bonds between the carbons and hydrogens within each hydrocarbon molecule.
AND
Intermolecular forces of attraction between different hydrocarbon molecules in the mixture.
What happens when curse oil is heated?
When the crude oil mixture is heated, the molecules are supplied with extra energy.
This makes the molecules move more. Eventually, a molecule might have enough energy to overcome the intermolecular forces that keep it with the other molecules.
It can then go whizzing off as a gas.
The covalent bonds holding each molecule together are stronger than intermolecular forces so they don’t break. This is why you end up with lots of little molecules.
The intermolecular forces break easily in small molecules than they do in bigger molecules. This is because intermolecular forces of attraction are stronger between big molecules than smaller ones.
This is why big molecules have higher boiling points than smaller molecules do- more energy is needed for them to break out of a liquid and form a gas.
What is refining and fractional distillation?
The process of separating crude oil is called refining and it’s done by fractional distillation.
In fractional distillation hydrocarbons are separated into groups with different boiling points.
Each group is called a fraction. And hydrocarbons within a fraction have similar boiling points.
Hydrocarbon chains have similar boiling points if they are similar lengths- so each fraction is made of hydrocarbons with similar chain lengths.
What are the useful products of crude oil?
After refining, here are the useful products:
- Refinery gas
- Petrol
- Naphtha (a base for chemicals)
- Kerosene (jet fuel)
- Diesel
- Lubricating oil
- Bitumen (for road surfaces)
What are the various uses of crude oil?
- The petrochemical industry refines crude oil to produce fuels and lubricants. It also makes raw materials for synthetic materials.
- Most hydrocarbons in crude oil are used to produce fuels.
- A small amount of hydrocarbons from crude oil are used to make new compounds for things like plastics,medicines,fertilisers and food.
- Less useful hydrocarbons can be split apart to make even more useful hydrocarbons and ethane.
- The process of making new compounds is called chemical synthesis.
What is polymerisation?
Plastics are formed when lots of small molecules called monomers join together to make a long molecule called polymers.
They are carbon based.
Under high pressure many small molecules polymerise to form long chains called polymers.
Different types of polymers?
- Strong rigid polymers such as high density polythene are used to make plastic milk bottles.
- Light stretchable polymers such as low density polythene are used for plastic bags. Low density polythene has a low melting point.
- PVC is strong and durable it can be made rigid or stretchy. It can be used for window frames and piping. The stretchy kind is used for synthetic leather.
- Polythene foam is used in packaging to protect breakable things. It is used for disposable coffee cups.
- Heat resistant polymers such as melamine resin and polypropene are used to make plastic kettles.
What polymers have replaced natural materials?
Synthetic fibres like nylon and polyester are often used to replace cotton,wool or silk.
The synthetic fibres tend to be lighter,more durable, water resistant and cheaper.
A disadvantage is that synthetic fibres are not breathable and are uncomfortable next to skin.
Rigid PVC has replaced wood for new window frames. It is weather resistant,strong and durable. Which makes the windows more secure- and don’t need painting as much as wood does.
However, PVC doesn’t look as good as wooden frames.
