Useful+Materials

= media type="custom" key="5730797" Useful Materials = = = =Plastics= Plastics are a reality of our world. They are unavoidable. But what are they exactly? Where do they come from? How are they made? And what should we do with them when we have used them. This unit touches on some of these questions.

Possible Pracs :
 * making plastics from milk
 * moulding plastics
 * modeling plastic molecules

Wikipedia //Plastics are man-made materials. Plastics have taken the place of traditional materials like woods and metals.// //Plastics differ from other materials largely because of the size of their molecules. Most materials have molecules made up of less than 300 atoms, plastics contain thousands of atoms. We call them Macromolecules.// //Some plastics are derived from natural substances such as animals, insects and plants but most are man-made. These are named Synthetic Plastics.// //Most synthetic plastics come from crude oil but coal and natural gas is also used.// //When crude oil is refined gasses are given off. The gasses are broken down into Monomers. These are chemical substances consisting of a single molecule. Thousands of these are linked together in a process called Polymerisation to form new compounds called Polymers.// ||  ||   ||
 * || **//Plastics//**

How bottles are made
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 * ===There are two main types of plastics and these are named Thermoplastics and Thermosetting Plastics.=== ||


 * //** Thermoplastics **// are made up of lines of molecules with few cross linkages. This allows them to soften when heated and to be bent into a variety of shapes and forms. They become stiff and solid again when cold. //This process can be repeated many times.// ||


 * //** Thermosetting Plastics **// are made up of lines of molecules which are heavily cross linked. It creates a rigid molecular structure. They may be heated the first time and shaped but they become permanently stiff and solid. They cannot be reshaped again. ||


 * //** Plastic Memory. **// Each time a plastic is reheated it will attempt to return to its original flat shape unless it has been over heated or damaged. This is called a plastic memory. ||

Environmental Policy at McDonalds
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 * Common recycling myths busted
 * Reduce, Reuse, Recycle - How to (Go Greener Aust)
 * The three RRR's explained [[file:Info3_The_3Rs.doc]]

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How can we reduce the negative effects of plastics and other wastes on the environment?

 * [[file:Thinking stratergies.doc]]








 * [[file:plastic bag myths.pdf]]
 * [[file:recycling.pdf]]
 * Ollie saves the planet

Task:
Read your text p. 27 - 30 and make notes on... Complete the "Over-To-You" questions on p.30
 * 1) Where the name **plastic** comes from? (page 27).
 * 2) What is **casein** and what did it used to be used for? (page 27).
 * 3) **Bakelite** was one of the first plastics. When was it invented and what was it used for?
 * 4) Define '**polymers**'. (page 27).
 * 5) Explain the process of **polymerization**. (page 27).
 * 6) Copy the diagram on page 28 and explain why **thermo-plastics** soften and can be shaped when heated gently.
 * 7) Copy the second diagram on page 28 and explain how the properties of **thermosetting**plastics (resins) stop them from being softened and remolded?
 * 8) Copy the diagram of an **injection mould** (page 28). Give reasons why injection mould ing is used for some products and extrusion moulding is used for others.
 * 9) Identify three **advantages** and three **disadvantages** of plastics. (page 29).
 * 10) Design a 'flier' encouraging people to **Reduce Reuse Recycle** (page 29). //Hint: visit the resources on www.sjesci.wikispaces.com for ideas.//
 * 11) Why did scientists invent a plastic that could **biodegrade**? How can this happen? (//Hint: There are a couple of ways//). (page 29).