Properties, Uses & Alloys Of Metals

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Physical Properties of Metals

Metals are good conductors of heat and electricity due to delocalised electrons that move through the structure.
Metals are malleable (can be hammered into shapes) and ductile (can be drawn into wires) because layers of positive ions can slide over each other.
Metals have high melting and boiling points because of strong metallic bonding (electrostatic attraction between positive ions and delocalised electrons).
Most metals are solids at room temperature (except mercury).
Metals are sonorous (make a ringing sound when struck).

Metallic bonding in aluminium

Chemical Properties of Metals

Metals react with water (cold or steam) to produce a metal hydroxide/oxide and hydrogen.
Metals react with dilute acids to produce a salt and hydrogen gas.
Metals react with oxygen to form metal oxides.
The reactivity series ranks metals based on their reactions with water, acid, and oxygen.

Uses of Aluminium

Aluminium is used for aeroplane bodies because of its low density and high strength-to-weight ratio.
Aluminium is used for overhead power cables because it is a good electrical conductor and has low density.
Aluminium is used for food cans because it is non-toxic and resistant to corrosion (forms a protective oxide layer).

Uses of Copper

Copper is used for electrical wiring because it is a very good conductor of electricity and is ductile.
Copper is used for pots and pans because it is a good conductor of heat, unreactive, and malleable.
Copper is used for water pipes because it is non-toxic, unreactive with water, and malleable.

Structure of an electrical cable

What is an Alloy?

An alloy is a mixture of a metal with other elements (often other metals, but may include non-metals).
Alloys are not compounds; they are physical mixtures.
Alloys have different properties from their constituent metals, often being stronger, harder, or more resistant to corrosion.

Examples of Alloys

Brass is an alloy of copper and zinc; it is stronger than either metal and used in musical instruments, ornaments, and door knobs.
Stainless steel is an alloy of iron with chromium, nickel, and carbon; it is hard and resistant to rusting, used in cutlery.
Iron with tungsten is extremely hard and resistant to high temperatures.
Aluminium with copper, manganese, and silicon is stronger but still low density, ideal for aircraft bodies.

Structure of Alloys (Extended Tier)

Pure metals have a regular arrangement of positive ions in layers surrounded by a sea of delocalised electrons.
In an alloy, atoms of different sizes distort the regular lattice, creating an irregular arrangement.
The distortion makes it harder for layers to slide over each other, so alloys are generally harder and stronger than pure metals.

Structure of an alloy

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練習問題

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1.Which of the following is a physical property of metals?
Easy
- AThey are brittle when solid.
- BThey are good conductors of electricity.
- CThey have low melting points.
- DThey are non-ductile.
2.What is the main reason metals are malleable?
Medium
- AThe atoms are arranged in a regular lattice that can slide.
- BThe delocalised electrons allow layers to slide over each other.
- CThe strong metallic bonds prevent any movement.
- DThe atoms are covalently bonded in a rigid structure.
3.What is an alloy?
Easy
- AA pure metal element.
- BA compound of two metals.
- CA mixture of a metal with other elements.
- DA non-metal combined with oxygen.
4.Which of the following is an alloy of copper and zinc?
Easy
- AStainless steel
- BBronze
- CBrass
- DSolder
5.Why are alloys generally harder than pure metals?
Medium
- AAlloys have a regular arrangement of atoms that is easier to slide.
- BAlloys contain atoms of different sizes that distort the layers, making sliding harder.
- CAlloys have more delocalised electrons than pure metals.
- DAlloys have weaker metallic bonds than pure metals.
6.Which metal is commonly used for electrical wiring due to its high conductivity and ductility?
Easy
- AAluminium
- BCopper
- CIron
- DGold
7.Which of the following is a use of aluminium based on its low density?
Easy
- AFood cans
- BElectrical wiring
- CAeroplane bodies
- DCutlery
8.Which statement about the structure of an alloy is correct?
Easy
- AIt has a regular arrangement of identical atoms.
- BIt has an irregular arrangement of atoms of different sizes.
- CIt has a regular arrangement of atoms of different sizes.
- DIt has an irregular arrangement of identical atoms.

もっと問題

9.Which property of copper makes it suitable for use in cooking pots?
Easy
- AIt is a poor conductor of heat.
- BIt is a good conductor of heat and unreactive.
- CIt has a low density.
- DIt is very hard.
10.What is the main reason stainless steel is used for cutlery?
Easy
- AIt is lightweight.
- BIt is hard and resistant to corrosion.
- CIt is a good conductor of electricity.
- DIt has a low melting point.
11.Which diagram best represents the structure of an alloy?
Medium
- ARegular rows of identical circles.
- BIrregular rows of circles of different sizes.
- CRandomly scattered individual circles.
- DRegular rows of circles of different sizes.
12.Brass is an alloy of copper and zinc. Which statement about brass is correct?
Medium
- ABrass is stronger than pure copper or zinc
- BBrass is weaker than pure copper or zinc
- CBrass is more ductile than pure copper
- DBrass is more malleable than pure copper
13.A student investigates the reaction of magnesium with dilute sulfuric acid. Which is a possible source of experimental error?
Medium
- ANot measuring the temperature immediately after adding magnesium
- BUsing a measuring cylinder to measure acid volume
- CStirring the solution
- DUsing excess acid
14.A student investigates the temperature change when equal lengths of magnesium ribbon react with excess dilute sulfuric acid of different concentrations. In Experiment 1, 20 cm³ of solution A is used. The initial temperature is 20.0 °C and the highest temperature is 28.5 °C. What is the temperature change?
Easy
- A8.5 °C
- B48.5 °C
- C20.0 °C
- D28.5 °C
15.In the same investigation, which experiment is expected to produce the largest temperature change?
Medium
- AThe experiment with the most concentrated acid
- BThe experiment with the least concentrated acid
- CThe experiment with the largest volume of acid
- DThe experiment with the smallest length of magnesium
16.What type of chemical reaction occurs when magnesium reacts with dilute sulfuric acid?
Easy
- AExothermic
- BEndothermic
- CNeutralisation
- DPrecipitation
17.In the investigation, which of the following is a possible source of experimental error?
Medium
- ANot stirring the mixture
- BUsing a measuring cylinder to measure acid
- CUsing magnesium ribbon from the same reel
- DRecording the highest temperature after 5 minutes
18.Why is aluminium used extensively in the manufacture of aeroplanes?
Easy
- AIt has a high strength-to-weight ratio and low density
- BIt is very dense and strong
- CIt is cheap and readily available
- DIt is a good conductor of electricity
19.In an experiment, equal masses of magnesium powder are used instead of equal lengths of magnesium ribbon. How would the temperature changes compare to using ribbon?
Medium
- AThey would be larger because powder has a larger surface area
- BThey would be smaller because powder reacts more slowly
- CThey would be the same because the mass of magnesium is the same
- DThey would be smaller because powder is less reactive
20.In the reaction between magnesium and dilute sulfuric acid, if 40 cm³ of acid is used instead of 20 cm³ (same concentration), what is the effect on the temperature change?
Hard
- AThe temperature change is about the same because the same amount of magnesium reacts
- BThe temperature change is larger because more acid is present
- CThe temperature change is smaller because the heat is spread over more volume
- DThe temperature change is zero because the reaction does not occur
21.Which type of chemical reaction occurs when magnesium reacts with dilute sulfuric acid?
Easy
- ANeutralisation
- BDisplacement
- CCombustion
- DOxidation
22.A student repeats an experiment using magnesium powder instead of ribbon, and uses the same mass. The temperature change is larger. What is the most likely reason?
Medium
- APowder has a larger surface area, so reaction is faster and more heat is released in a shorter time
- BPowder has a smaller surface area, so reaction is slower and heat is lost
- CPowder is more reactive than ribbon
- DPowder reacts with a different mechanism
23.In an experiment, equal lengths of magnesium ribbon are added to 20 cm³ of sulfuric acid of different concentrations. The temperature change is recorded. Which graph best shows the expected relationship between concentration and temperature change?
Hard
- AA positive linear relationship
- BA negative linear relationship
- CNo relationship
- DA curve that increases then levels off
24.A student measures the temperature change when 1 g of magnesium powder reacts with excess sulfuric acid. The experiment is repeated using 2 g of magnesium powder. How does the temperature change compare?
Medium
- AIt is about double
- BIt is about the same
- CIt is half
- DIt is four times
25.In an experiment, 20 cm³ of sulfuric acid at 20°C is reacted with magnesium. The highest temperature reached is 28°C. If the experiment is repeated with the same volume of acid at 30°C, what would be the expected highest temperature?
Hard
- A38°C
- B28°C
- C30°C
- D48°C
26.Metals conduct electricity because they have delocalised electrons that can move through the metal structure.
Easy
True or false?
27.Non-metals are generally malleable and ductile.
Easy
True or false?
28.Which of the following is a property of non-metals?
Easy
- AGood conductors of heat and electricity
- BMalleable and ductile
- CLow melting and boiling points
- DHigh density
29.Which property makes aluminium suitable for use in overhead power cables?
Medium
- AHigh density and strength
- BLow density and good electrical conductivity
- CHigh melting point and magnetic properties
- DReactivity and resistance to corrosion
30.Copper is used for electrical wiring mainly because it is:
Easy
- Avery strong and hard
- Ba very good conductor of electricity and ductile
- Cnon-toxic and has a low density
- Dresistant to corrosion and magnetic
31.Stainless steel is an alloy of iron with chromium and nickel, and it is used for cutlery because it is hard and resistant to corrosion.
Easy
True or false?
32.Arrange the following steps in the correct order to explain why alloys are harder than pure metals.
Medium
- Atoms of different sizes are added to the metal.
- The regular arrangement of atoms is distorted.
- Layers of atoms cannot slide over each other easily.
- The alloy is harder and stronger than the pure metal.
33.Which of the following are properties of metals? (Select all that apply)
Medium
- AConduct heat and electricity
- BBrittle when solid
- CMalleable and ductile
- DUsually have high melting and boiling points
- ELow density
34.Match each use of aluminium to the correct property.
Medium
- aeroplane bodies
- overhead power cables
- food cans
- good electrical conductor, low density
- high strength-to-weight ratio, low density
- non-toxic, resistant to corrosion and acidic foods
35.Complete the sentence.
Easy
The ability of metals to be hammered into shapes is called ____.
36.Explain why aluminium does not corrode easily, even though it is a reactive metal.
Medium
37.Complete the sentence about the reaction of metals with acids.
Easy
When a metal reacts with an acid, the products are a ____ and ____ gas.

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