Unit 8 Materials and machines 1.- Natural materials and man made materials Materials are the substances the things are made of. There are 2 types: A) Natural materials They are found in nature. They come from :
Animals: wool, leather, silk… Plants: wood, cotton… Minerals: rocks (granite, marble…) , minerals (gold, precious stones…)
B) Man made materials are materials made by people using raw materials. Examples of man made materials are paper that comes from wood, iron that comes from different minerals or plastic that is obtained from petroleum.
2.- Machines Machines are objects we use to make work easier. They help us to save time and energy. (scissors, telephones…) All machines use energy to work. It can work using:
Human energy (wheelbarrow, bycicle…) Electrical energy (Computer, fridge…) Energy from petrol (car), from water (watermills) or wind (windmills)
2.1 Machines are used for different things: To apply force (hammer), to transport things (motorbike), to heat or cool things (freezer), to communicate things (mobile phones), to process information (computers)… 2.2 Types of machines A) Simple machines. They have only one part or few parts using human energy. The pulley, the inclined plane and the lever are common simple machines. B) Complex machines are made of many parts (Motors, gears…)
3.-Inventions Inventions are new objects made by people to make our lives better. The first inventions were simple machines.
Inventions for transport. (motor, cars, aeroplanes, buses…) Inventions for communication ( printing press, radio, television, computers…) Inventions for the home (refrigrator, washing machine, vacuum cleaner…)