English narration · English + 中文 subtitles burned in · 英語ナレーション・英語＋中文字幕 burning-in
9.1
Properties of metals · 金属の性質
Syllabus · シラバス
English
Core
Supplement
1 Compare the general physical properties of metals and non-metals, including: (a) thermal conductivity (b) electrical conductivity (c) malleability and ductility (d) melting points and boiling points
2 Describe the general chemical properties of metals, limited to their reactions with: (a) dilute acids (b) cold water and steam (c) oxygen
Source: Cambridge International syllabus · 出典: Cambridge International シラバス
English
Physical properties
Metals 金属 and non-metals 非金属 behave very differently:
Property
Metals
Non-metals
thermal conductivity 导热性 (conducting heat)
good
poor
electrical conductivity 导电性
good
poor (except graphite)
malleability 展性 and ductility 延性
malleable and ductile
brittle 易碎 (they snap)
melting point 熔点 and boiling point 沸点
usually high
usually low
Chemical properties
Metals react in three main ways:
with dilute acids 酸 → a salt 盐 + hydrogen 氢气
with cold water or steam 蒸汽 → a metal hydroxide (or oxide) + hydrogen
with oxygen 氧气 → a metal oxide 氧化物
日本語
物理的性質
金属と非金属は非常に異なる振る舞いを示す：
性質
金属
非金属
熱伝導率（熱を伝える能力）
良い
悪い
電気伝導率
良い
悪い（グラファイトを除く）
展性および延性
展性および延性がある
脆い（折れる）
融点および沸点
通常高い
通常低い
化学的性質
金属は主に3つの方法で反応する：
希酸 → 塩 + 水素
冷水または蒸気 → 金属水酸化物（または酸化物）+ 水素
酸素 → 金属酸化物
自然銅：金属は光沢があり、密度が高く、展性・延性があり、熱と電気の良質な伝導体である
Explore · 探索
Metallic bonding · 金属結合
Positive ions sit in a sea of delocalised electrons — that is why metals conduct and bend. Push the layers and the bond holds. · 正イオンは非局在電子の海の中に配置されている——これが金属が電気伝導性を持ち、曲げられる理由である。層を押し付けると結合は保たれる。
Explore · 探索
Metal property lab · 金属の性質実験
Link metal properties to the particle model. · 金属の性質と粒子モデルを関連付ける。
1 Describe the uses of metals in terms of their physical properties, including: (a) aluminium in the manufacture of aircraft because of its low density (b) aluminium in the manufacture of overhead electrical cables because of its low density and good electrical conductivity (c) aluminium in food containers because of its resistance to corrosion (d) copper in electrical wiring because of its good electrical conductivity and ductility
1 Describe an alloy as a mixture of a metal with other elements, including: (a) brass as a mixture of copper and zinc (b) stainless steel as a mixture of iron and other elements such as chromium, nickel and carbon
2 State that alloys can be harder and stronger than the pure metals and are more useful
5 Explain in terms of structure how alloys can be harder and stronger than the pure metals because the different sized atoms in alloys mean the layers can no longer slide over each other
3 Describe the uses of alloys in terms of their physical properties, including stainless steel in cutlery because of its hardness and resistance to rusting
4 Identify representations of alloys from diagrams of structure
Source: Cambridge International syllabus · 出典: Cambridge International シラバス
English
An alloy 合金 is a mixture 混合物 of a metal with one or more other elements.
Brass 黄铜 is a mixture of copper and zinc 锌.
Stainless steel 不锈钢 is a mixture of iron 铁 with other elements such as chromium 铬, nickel 镍 and carbon 碳.
Alloys are usually harder and stronger than the pure metals, which makes them more useful. For example, stainless steel is used for cutlery because it is hard and does not rust.
Why alloys are harder. In a pure metal, the atoms 原子 are all the same size, so the layers 层 can slide over each other easily. In an alloy, the different-sized atoms stop the layers from sliding, so the alloy is harder and stronger.
1 State the order of the reactivity series as: potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, iron, hydrogen, copper, silver, gold
4 Describe the relative reactivities of metals in terms of their tendency to form positive ions, by displacement reactions, if any, with the aqueous ions of magnesium, zinc, iron, copper and silver
2 Describe the reactions, if any, of: (a) potassium, sodium and calcium with cold water (b) magnesium with steam (c) magnesium, zinc, iron, copper, silver and gold with dilute hydrochloric acid and explain these reactions in terms of the position of the metals in the reactivity series
5 Explain the apparent unreactivity of aluminium in terms of its oxide layer
3 Deduce an order of reactivity from a given set of experimental results
(most reactive at the top, least reactive at the bottom)
The higher a metal is, the more easily it forms positive ions 离子. This explains its reactions:
potassium, sodium and calcium react with cold water.
magnesium reacts with steam (but only very slowly with cold water).
magnesium, zinc and iron react with dilute hydrochloric acid; copper, silver and gold do not.
Displacement reactions
A more reactive metal will displace a less reactive metal from a solution of its ions (a displacement reaction 置换反应). For example, zinc displaces copper from copper(II) sulfate solution, because zinc is more reactive than copper:
Be ready to say what you would see, because those are separate marks:
the blue colour of the solution fades - the blue $\text{Cu}^{2+}$ ions are being used up (zinc sulfate is colourless).
a pink-brown solid coats the zinc - that is the displaced copper.
the grey zinc dissolves and gets smaller.
the mixture warms up - displacement is exothermic.
Metal-and-acid reactions have their own list: effervescence 泡腾 (the hydrogen escaping) and the solid dissolves. With copper(II) oxide or carbonate and acid, add that the solution turns blue. Never write "hydrogen is given off" as an observation - you cannot see the gas, only the bubbles, so write effervescence.
Worked example. Zinc and aluminium are both found as oxides. Which can be extracted by heating with carbon, and why? Find each metal's place relative to carbon in the reactivity series. Zinc sits below carbon, so carbon is the more reactive of the two and can take the oxygen away from it: zinc oxide is reduced by heating with carbon. Aluminium sits above carbon, so carbon is not reactive enough to displace it, and aluminium must be extracted by electrolysis instead - which is why aluminium costs far more to extract. The line in the series that decides the method is carbon's, not the top of the list.
The special case of aluminium
Aluminium seems less reactive than its position suggests. This is because it is covered by a thin, strong oxide layer 氧化层 that stops other substances reaching the metal underneath.
** worked example. 亜鉛とアルミニウムはどちらも酸化物として存在する。どちらを炭素と加熱して抽出できるか、またなぜか？ 反応性系列において各金属の炭素に対する位置を確認する。亜鉛は炭素の下にあるため、炭素の方がこの2つの中で反応性が高く、酸素を取り除くことができる：炭素と加熱することで酸化亜鉛は還元される。アルミニウムは炭素の上にあるため、炭素はそれを置換するだけの反応性を持たず、代わりにアルミニウムは電解法**で抽出されなければならない——これがアルミニウムの抽出コストが非常に高い理由である。方法を決定するのは系列の最上段ではなく、炭素のラインである。
Displacement and the reactivity series · 置換反応と反応性系列
Step through a displacement. A more reactive metal pushes a less reactive one out of its compound — which is exactly what the reactivity series predicts. · 置換反応の流れを確認しましょう。より反応性の高い金属は、より反応性の低い金属をその化合物から押し出します——これはまさに反応性系列が予測することです。
1 State the conditions required for the rusting of iron and steel to form hydrated iron(III) oxide
2 State some common barrier methods, including painting, greasing and coating with plastic
4 Describe the use of zinc in galvanising as an example of a barrier method and sacrificial protection
3 Describe how barrier methods prevent rusting by excluding oxygen or water
5 Explain sacrificial protection in terms of the reactivity series and in terms of electron loss
日本語
コア
サプリメント
1 鉄および鋼が水化第三酸化鉄となるために必要な条件を記述せよ
2 塗装、脂塗り、プラスチックコーティングなどの一般的なバリア方法を列挙する
4 亜鉛を用いたメッキをバリア方法および犠牲的保護の例として記述する
3 バリア方法が酸素または水を排除することで錆びを防ぐ仕組みを記述する
5 反応性の順序および電子の損失の観点から、犠牲的保護を説明する
Source: Cambridge International syllabus · 出典: Cambridge International シラバス
English
Rusting 生锈 is the corrosion of iron and steel. Two things are needed for rusting: oxygen (from the air) and water. The rust 铁锈 formed is hydrated iron(III) oxide.
Stopping rust
Barrier methods 隔离法 keep oxygen and water away from the iron:
painting, greasing (covering with oil), and coating with plastic.
Galvanising 镀锌 means coating iron with a layer of zinc. This works in two ways:
it is a barrier (the zinc keeps out air and water);
it gives sacrificial protection 牺牲保护. Because zinc is more reactive than iron, the zinc loses electrons 电子 and corrodes instead of the iron — even if the surface is scratched.
Why iron rusts — and how to stop it · 鉄が錆びる理由と防止方法
Step through rusting. Iron needs BOTH water and oxygen, and once it starts the rust flakes off to expose fresh metal — which is why we protect iron. · 錆びる流れを確認しましょう。鉄には水と酸素の両方が必要であり、一度錆び始めると錆が剥がれて新鮮な金属が露出するため、鉄を保護するのです。
1 Describe the ease in obtaining metals from their ores, related to the position of the metal in the reactivity series
2 Describe the extraction of iron from hematite in the blast furnace, limited to: (a) the burning of carbon (coke) to provide heat and produce carbon dioxide (b) the reduction of carbon dioxide to carbon monoxide (c) the reduction of iron(III) oxide by carbon monoxide (d) the thermal decomposition of calcium carbonate/limestone to produce calcium oxide (e) the formation of slag Symbol equations are not required
4 State the symbol equations for the extraction of iron from hematite (a) $\text{C} + \text{O}_2 \rightarrow \text{CO}_2$ (b) $\text{C} + \text{CO}_2 \rightarrow 2\text{CO}$ (c) $\text{Fe}_2\text{O}_3 + 3\text{CO} \rightarrow 2\text{Fe} + 3\text{CO}_2$ (d) $\text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2$ (e) $\text{CaO} + \text{SiO}_2 \rightarrow \text{CaSiO}_3$
3 State that the main ore of aluminium is bauxite and that aluminium is extracted by electrolysis
5 Describe the extraction of aluminium from purified bauxite/aluminium oxide, including: (a) the role of cryolite (b) why the carbon anodes need to be regularly replaced (c) the reactions at the electrodes, including ionic half-equations Details of the purification of bauxite are not required
Source: Cambridge International syllabus · 出典: Cambridge International シラバス
English
How a metal is taken from its ore 矿石 depends on its place in the reactivity series. Metals below carbon can be extracted by heating with carbon (which removes the oxygen). Metals above carbon are too reactive for this and must be extracted by electrolysis 电解.
Iron from the blast furnace
Iron is extracted from its ore hematite 赤铁矿 (iron(III) oxide) in a blast furnace 高炉:
Carbon (coke) burns in hot air to give carbon dioxide and lots of heat.
This carbon dioxide 二氧化碳 reacts with more carbon to form carbon monoxide 一氧化碳.
The carbon monoxide reduces the iron(III) oxide to iron (this is reduction 还原).
Limestone 石灰石 (calcium carbonate) breaks down in the heat to form calcium oxide 氧化钙.
The calcium oxide reacts with sandy impurities to form slag 炉渣, which is removed.
Aluminium by electrolysis
Aluminium is extracted from its ore bauxite 铝土矿 (purified to aluminium oxide) by electrolysis:
The aluminium oxide is dissolved in molten cryolite 冰晶石 to lower its melting point and save energy.
At the cathode 阴极, aluminium ions gain electrons to form aluminium metal.
At the anode 阳极, oxygen is formed. This oxygen reacts with the hot carbon anodes and burns them away, so they must be replaced regularly.
Learn the reactivity series (potassium → gold). A more reactive metal displaces a less reactive one from a solution of its ions.
Metals above carbon are extracted by electrolysis; those below carbon (like iron) can be extracted by heating with carbon.
Rusting needs both water and oxygen. Barrier methods (paint, oil) keep them out; galvanising also gives sacrificial protection, because the more reactive zinc corrodes instead of the iron.
Alloys are harder than pure metals because the different-sized atoms stop the layers of ions sliding over each other.
Type to search notes, lessons, code, vocabulary and past-paper questions across every subject. · すべての科目でノートImplemented、Implemented、コード、語彙、過去問問題を検索するために入力してください。
