Choosing the Right Material

选择合适的材料 · P3 Science · Pages 59–66
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🟢 Paragraph 1 · Materials for Different Purposes 不同用途的材料
Materials are used to make objects. Objects are things you use for different purposes. Every material has physical properties. The physical properties of a material allow it to be used in certain ways. Let us consider some of the common objects in our homes. A bath towel is made of fabric because fabric absorbs water. Scissors are made of metal because metal is strong and can cut through things. A raincoat is made of plastic because plastic is waterproof. A water hose is made of rubber because rubber is flexible and waterproof.
材料被用来制作各种物品,物品就是我们日常使用的东西,它们有着不同的用途。每种材料都有物理特性。材料的物理特性决定了它的使用方式。让我们看看家里常见的一些物品。浴巾布料做的,因为布料能吸水剪刀金属做的,因为金属坚固,能剪断东西。雨衣塑料做的,因为塑料防水水管橡胶做的,因为橡胶柔韧又防水。
💡 想想为什么浴巾不能用塑料做?因为塑料不吸水呀!每种材料都有最适合它的用途。
🟢 Paragraph 2 · Real-World Examples 生活中的例子
Curtains are made of fabric because fabric is flexible, which allows the curtain to be folded at the side of the window. Some types of fabric are also opaque, which allows them to block out sunlight entering the house on a bright, sunny day. Metal trolleys are able to hold the weight of heavy groceries without bending. Trolleys are usually made of metal because metal is rigid and strong. A fish tank is made of glass because glass is transparent. Transparent materials allow us to see the fishes and plants inside the tank clearly. Glass is also waterproof so water in the tank will not leak out. Gloves are often made of rubber because rubber is waterproof and flexible.
窗帘布料做的,因为布料柔韧,可以折叠到窗户一侧。有些布料还是不透明的,可以在晴天挡住阳光进入房间。金属手推车能承受沉重的日用品而不弯曲。手推车通常是金属做的,因为金属坚硬牢固鱼缸玻璃做的,因为玻璃是透明的。透明的材料让我们能清楚地看到缸里的鱼和植物。玻璃还是防水的,所以缸里的水不会漏出来。手套通常是橡胶做的,因为橡胶防水又柔韧。
💡 为什么鱼缸不能用木头做?因为木头不透明,看不到鱼;而且木头会吸水!
🟢 Paragraph 3 · Same Object, Different Materials 同一物品,不同材料
An object can be made from different materials. The choice of materials depends on the use of the object. A container used to contain drinking water at home can be made of plastic, glass or metal. Plastic, glass and metals are waterproof, so they are useful for containing drinks. Clear plastic and glass are transparent so you can easily tell when the bottle is full or not. However, metal is not transparent. Glass is not as strong as plastic or metal. A container made of glass will break easily when dropped. This is why you have to be careful when handling a container made of glass.
同一种物品可以用不同的材料来制作。材料的选择取决于物品的用途。家里装饮用水的容器可以用塑料玻璃金属做成。塑料、玻璃和金属都是防水的,所以适合用来装饮料。透明塑料和玻璃是透明的,你可以很容易地看出瓶子是满的还是空的。但金属不透明。玻璃不如塑料或金属坚固,玻璃容器掉在地上容易。所以拿玻璃容器的时候要特别小心。
💡 想想你平时喝水用什么杯子?如果去野外玩,你会选玻璃杯还是塑料杯?为什么?
🟢 Paragraph 4 · Many Materials Make One Object 多种材料组成一个物品
An object can be made out of different materials put together. This is because objects like cars have many parts. These different parts of an object have different purposes. The materials are selected for the different parts based on their physical properties. Car tyres are made of rubber because rubber is strong and flexible. Fabric is used to make the car seat because it is flexible and comfortable. Metal is used to make the car body because metal is strong and does not break easily. It protects the driver and passengers from injury in a car accident. Glass is used to make the windscreen because glass is transparent and waterproof. Knowing the physical properties of a material is important when designing and making new products.
一个物品可以由多种不同的材料组合而成。这是因为像汽车这样的物品有很多部件。这些不同的部件有着不同的用途。根据物理特性来为不同部件选择合适的材料。汽车轮胎是用橡胶做的,因为橡胶坚固柔韧布料用来做汽车座椅,因为它柔韧又舒适金属用来做车身,因为金属坚固不易碎,能在车祸中保护驾驶员和乘客免受伤害。玻璃用来做挡风玻璃,因为玻璃透明防水。了解材料的物理特性对于设计和制造新产品非常重要。
💡 想想一辆汽车——轮胎(橡胶)、座椅(布料)、车身(金属)、车窗(玻璃),每种材料都有自己的任务!
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