📚 Material Properties | 材料性质
Materials are all around us, but not all materials behave in the same way. In KS3 Chemistry, we study material properties to understand why metals are used for saucepans, why plastics make good drinks bottles, and why glass is chosen for windows. A property is a characteristic that helps us describe, compare, and choose a material for a particular job.
材料在我们的生活中无处不在，但不同材料的表现并不相同。在 KS3 化学中，我们学习材料性质，是为了理解为什么金属可用来做锅、为什么塑料适合做饮料瓶、为什么玻璃被选来做窗户。性质是一种特征，它帮助我们描述、比较材料，并为特定用途选择合适的材料。
1. What Are Material Properties? | 什么是材料性质？
A material property is any feature that can be observed or measured without changing the substance into a new substance. Physical properties include hardness, density, melting point, boiling point, electrical conductivity and thermal conductivity. Chemical properties describe how a material reacts with other substances, such as flammability and reaction with acids.
材料性质是指在不把物质变成新物质的情况下可以观察或测量的任何特征。物理性质包括硬度、密度、熔点、沸点、导电性和导热性。化学性质描述材料如何与其他物质发生反应，例如可燃性以及与酸的反应。
At KS3, we separate properties into two groups: physical properties and chemical properties. Physical properties can usually be tested using simple equipment such as a balance, ruler, magnet or circuit. Chemical properties are tested by seeing whether a new substance forms after a reaction.
在 KS3 阶段，我们把性质分为两类：物理性质和化学性质。物理性质通常可以用天平、尺子、磁铁或电路等简单设备进行测试。化学性质则需要观察反应后是否生成了新物质来判断。
2. Hardness and Strength | 硬度与强度
Hardness measures how difficult it is to scratch or dent a material. Diamond is extremely hard, so it is used in cutting tools. Talc is very soft and can be scratched with a fingernail. Hardness is not the same as strength; a material can be hard but brittle, like glass.
硬度衡量的是材料被划伤或压凹的难易程度。金刚石非常坚硬，因此被用于切割工具。滑石非常软，用指甲就能划出痕迹。硬度与强度并不相同；一种材料可以坚硬但易碎，例如玻璃。
Strength describes how well a material resists breaking when a force is applied. Steel has high tensile strength, meaning it can be stretched by a large force before it snaps. Concrete is strong under compression, which makes it useful for building foundations.
强度描述的是材料在受力时抵抗断裂的能力。钢具有很高的抗拉强度，这意味着它在断裂前能承受很大的拉力。混凝土抗压强度高，因此适合用于建筑地基。
Hardness = resistance to scratching; Strength = resistance to breaking under force
硬度 = 抵抗刮擦的能力；强度 = 受力时抵抗断裂的能力
3. Density and Buoyancy | 密度与浮力
Density tells us how much mass is packed into a certain volume. It is calculated by dividing mass by volume. A material with high density, such as lead, feels heavy for its size. A material with low density, such as cork, feels light and often floats.
密度告诉我们在一定体积内聚集了多少质量。它的计算方法是质量除以体积。高密度材料（如铅）相对于体积会感觉很重。低密度材料（如软木）感觉很轻，而且常常能漂浮。
density = mass ÷ volume
密度 = 质量 ÷ 体积
Buoyancy is linked to density. An object floats if its overall density is less than the density of the liquid it is placed in. This is why steel ships can float: the ship's average density is lowered by the air inside its hull.
浮力与密度相关。如果物体的整体密度小于它所处液体的密度，物体就会漂浮。这就是钢制轮船能浮起来的原因：船体内部的空气降低了船的平均密度。
4. Melting and Boiling Points | 熔点与沸点
The melting point is the temperature at which a solid changes into a liquid. The boiling point is the temperature at which a liquid changes into a gas. These properties are different for every pure material and can be used to identify substances.
熔点是固体变为液体的温度。沸点是液体变为气体的温度。每种纯净物质的熔点和沸点都不同，因此可以用来鉴别物质。
Water has a melting point of 0 °C and a boiling point of 100 °C at normal pressure. Iron has a much higher melting point of about 1538 °C, so it is chosen for engine parts that must survive great heat.
水在常压下的熔点是 0 °C，沸点是
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