Core Science Chapter 2

7/24/2019 Core Science Chapter 2

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ELEMENTS'Introduction

Elements are the simplest pure substances. They cannot

be broken down into anything simpler by chemical

means. The periodic table of the elements lists about

116 known elements. Of these, hydrogen is by far the

most abundant element in the universe. On Earth, oxygen

is the most abundant element due to its presence in

many rock-making minerals as well as its important rolesin the hydrosphere, atmosphere and biosphere. The great

majority of elements occur naturally but some have been

synthesised using high-powered particle accelerators.

In this chapter

2.1 Classifying elements page 40

2.2 The properties and uses of elements page 46

8]VeiZg

Figure 2.1

Blue-black crystals of the non-metal iodine sublime toproduce a purple vapour composed of diatomic iodinemolecules.


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40 THE CHEMICAL EARTH

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Figure 2.2

Titanium (above) is a metal with alow density while platinum (right) has

a high density.

The physical properties of elementsEvery pure substance has its own unique set of physical properties. Thesephysical properties include:

melting point the lowest temperature at which a solid changes to aliquid at normal atmospheric pressure (100 kPa).

boiling point the lowest temperature at which a liquid changes to avapoursuch that the vapour exerts a pressure of 100 kPa.

density the mass of the substance per unit volume, measured at 25 Cand 100 kPa.

electrical conductivity the quantity of electric current transmittedthrough a unit cube of the material when there is a potential differenceof 1 volt across the cube.

thermal conductivity the rate at which heat energy is transferred througha unit cube of the material when there is a 1 temperature differenceacross the cube.

These properties can be used to check whether an element is 100% pure

or contaminated by impurities. Chemical data books provide lists of thesephysical properties for each natural element. Table 2.1 gives examples ofthese physical properties for some common elements, showing that thesethree elements are quite different. A chemist can check whether a sampleof copper is pure by measuring its physical properties. If the melting pointof the copper sample is not 1085 C, the sample must be contaminated withimpurities. Impurities tend to lower the melting points of pure substances.Similarly, if a copper sample is impure, its density will not be 8.96 g/cm3.

Table 2.1Physical properties of some common elements.

Element copper iodine silicon

Melting point (C) 1085 114 1410

Boiling point (C) 2572 184 3267

Density (g/cm3) 8.96 4.94 2.3

Electrical conductivity (MS/m) 58.4 11013 1103

Thermal conductivity (J/s/m/K)* 401 0.45 148

(*K Kelvin temperature units each Kelvin unit is the same size as a Celsius degree;100 C = 373 K and 0 C 273 K)vapour:the gaseous form of

a substance that is normallya solid or liquid at standardtemperature and pressure

Remember

Before beginning this section,you should be able to: describe the behaviour of

matter in terms of particlesthat are continuously moving

and interacting relate properties of solids,

liquids and gases to theparticle model of matter

relate changes of state to themotion of particles as energyis removed or added

explain density in terms of asimple particle model

classify elements as metals ornon-metals according to theircommon characteristics

identify internationallyrecognised symbols forcommon elements.

Key content

By the end of this section, youshould be able to: classify elements as metals,

non-metals and semi-metalsaccording to their physicalproperties

plan and perform aninvestigation to examine somephysical properties, includingmalleability, hardness andelectrical conductivity, and topresent information about theclassification of elements asmetals, non-metals orsemi-metals

process information fromsecondary sources and use

the periodic table to presentinformation about theclassification of elements as: metals, non-metals and

semi-metals solids, liquids and gases

at 25 C and normalatmospheric pressure.


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CHAPTER 2 ELEMENTS 41

The mass and volume of a sample of copper were measured:

mass of sample (m) 123.86 gvolume of sample (V) 14.00 cm3

Calculate the density of the sample and determine whether the sampleis pure or impure.

d m/V

123.86/14.00

8.85 g/cm3

This density is slightly lower than that of pure copper (8.96g/cm3) sothe sample is slightly impure.

SAMPLE PROBLEM 2.1

SOLUTION

A student uses an electronic temperature probe and data logger tomeasure the temperature of a sample of lead as it was heated slowly anduniformly from 320 C to 336 C. The results are shown in table 2.2.

Table 2.2

Time (min) 0 1 2 3 4 5 6 7 8 9

Temperature (C) 320 323 326 327 327 327 328 330 333 336

(a) Plot the data as a line graph.

(b) Chemical data books list the melting point of lead as 327 C. (i) Identify the region of the graph that corresponds to the

melting point of lead. (ii) Account for the shape of the graph. (iii) The student concludes that the sample of lead is pure.

Justify this conclusion.

(a)

(b) (i) The plateau or inflexion region corresponds with themelting point of lead.

(ii) The temperature rises uniformly from 320 C to 326 C. Therate of temperature rise then slows, and the temperaturestops rising while the lead is melting. The added heatdoes not raise the temperature of the lead but causes it tochange state. Once all the lead has melted (between 5 and6 minutes), the temperature rises once more as the addedheat warms the melted lead.

(iii) The student is correct because the lead has a constant(fixed) melting point that matches the literature data.Impure lead would not have a distinct melting point and anyimpurities would reduce the melting point below 327 C. Wewould not expect a plateau region in the temperaturetimegraph if the sample were impure.

SAMPLE PROBLEM 2.2

SOLUTION

Temperature(C)

0 2 4

Time (minutes)

6 8 10

318

320

322

324

326

328

330

332334

336

338

Figure 2.3

Investigating thephysical propertiesof elements

2.1PRACTICALACTIVITIES


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SYLLABUS FOCUS

Figure 2.4

Some elements are named

for their properties, such as

their colour (far right), while

others are named after famous

scientists, such as Marie and

Pierre Curie (above),

or figures in mythology, such

as Thor (right).

Table 2.3Origins of some element names

Element Symbol

Source of

element name Category

curium Cm Pierre and Marie Curie scientist

germanium Ge Germany country

helium He helios, Greek word for Sun astronomy

iodine I iodes, Greek word for violet property

thorium Th Thor (Norse god of war) mythology

5. USING SYMBOLS TO IDENTIFY ELEMENTS

The study of chemistry is simplified by the use of symbols. Each element is identified by a unique

symbol that consists of one or two letters. The first letter is written in uppercase. If there is a second

letter, it is written in lowercase. The symbols chosen for elements are not always related to theirEnglish names. The symbols for some elements are based on its Latin, Greek or German name. For

example, the symbol for gold is Au (from the Latin word aurum). Elements are often named after

mythological gods, countries, scientists, properties or astronomical objects. For example, gallium is

named after Gallia, the ancient name for France. Table 2.3 gives the origins of some element names.

Use the periodic table on the inside cover of this book to find other examples.


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Classifying elements according to their

physical propertiesThe known elements may be classified conveniently into groups on thebasis of their physical properties. We will consider two of these groupings:physical state, and metallic or non-metallic properties.

Physical stateElements can be classified as solids, liquids or gases at standard temperatureand pressure (25 C and 100 kPa). The vast majority of elements are solids.Two elements are liquids (bromine and mercury) and eleven are gases.Table 2.4 lists the gases of the periodic table. Note that some gaseouselements exist as diatomic molecules. These elements mainly occupy theupper right corner of the periodic table.

Table 2.4Gaseous elements

H2 He N2 O2 F2 Ne Cl2 Ar Kr Xe Rn

Heating and cooling can convert elements from one state to another.

For example, gallium, which has a melting point of 30 C, can be liquefiedby holding it in your hand. Other elements require much more heat tomelt them.

Metals, non-metals and semi-metals

Another common way of classifying elements is to group them according

to their metallic or non-metallic properties. Elements that do not fit con-veniently into either group are called semi-metals.

Chemists use a range of physical properties to classify elements into oneof these three groups. The most important of these properties are lustre,electrical conductivity and malleability. In general:

metals are lustrous, malleable and ductile, and have a high electricalconductivity

semi-metalshave a low sheen, are moderately malleable and have semi-conductor properties

non-metalsare dull, brittleand non-conductors of electricity.

lustrous:shiny

malleable:able to be shapedwithout breaking by rolling,hammering or pressing

ductile:able to be drawn intowires without breaking

brittle:describes a substancethat shatters into fragmentswhen hammered

lustrous:shiny

malleable:able to be shapedwithout breaking by rolling,hammering or pressing

ductile:able to be drawn intowires without breaking

brittle:describes a substancethat shatters into fragmentswhen hammered

diatomic molecule:a moleculeconsisting of two atomschemically bonded together

Elements A, B and Chave the following melting (m.p.) and boiling(b.p.) points.

Element A: m.p. = 71 C, b.p. = 62 C Element B: m.p. = 39 C, b.p. = 357 C Element C: m.p. = 2610 C, b.p. = 5560 CClassify these elements as solid, liquid or gas at standard temperatureand pressure.

ElementA

has both melting and boiling points below 25C so it is agas at standard temperature and pressure. (This is the radioactive gasradon.)Element Bis a liquid at room temperature as its melting point is below25C but its boiling point is above 25C. (This is the liquid metalmercury.)Element C is a solid at room temperature as both its meltingand boiling points are well above 25C. (This is the heavy metalmolybdenum.)

SAMPLE PROBLEM 2.3

SOLUTION


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Table 2.5 provides a summary of the physical properties of metals, semi-metals and non-metals, and some representative examples. In the year2005, 116 elements were known. Of these, 92 are classified as metals, 7 assemi-metals and 17 as non-metals. (Note:At the time of writing, element117 had not been synthesised. The discovery of the synthetic elementununoctium (118) has been retracted.)

Table 2.5Physical properties of metals, semi-metals and non-metals

Group metals semi-metals non-metals

Appearance lustrous low sheen dull

Electrical conductivity high low(semi-conductors)

nil(insulators)

Thermal conductivity high high low(insulators)

Malleability and ductility high moderate nil (brittle)

Density generallyhigh

intermediate low

Boiling point generallyhigh

very high low

Strength high variable low

Examples sodium,magnesium,

iron,chromium,

zinc,

platinum,gold,mercury,lutetium

boron,silicon,

germanium,arsenic,

antimony,

tellurium,astatine

hydrogen,helium,carbon,

nitrogen,oxygen,

fluorine,neon,phosphorus

Table 2.6 compares some of the physical properties of a typical metal,semi-metal and non-metal.

Table 2.6Properties of a typical metal, semi-metal and non-metal

Element silver (metal) silicon(semi-metal)

sulfur(non-metal)

Lustre high moderately high low

Electrical

conductivity

(MS/m)

63 1 r103 1 r1021

Density (g/cm3) 10.5 2.3 2.1

Melting point (C) 962 1410 113

Boiling point (C) 2212 3267 445

DATAANALYSIS

2.2

Classifying elements


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2.1 QUESTIONS

1. Select the element that is classified as asemi-metal.

A TungstenB Fluorine

C XenonD Boron

2. Select the element that is classified as ametal.

A TelluriumB IridiumC SiliconD Germanium

3. Use the melting (m.p.) and boiling (b.p.)points provided to classify the followingelements as solids, liquids or gases at 25 Cand 100 kPa.

(a) Xenon (m.p. 112 C, b.p. 108 C)(b) Iridium (m.p. 2450 C, b.p. 4500 C)(c) Caesium (m.p. 28 C, b.p. 669 C)(d) Barium (m.p. 725 C, b.p. 1640 C)

4. The density of a sample of platinum wasdetermined by measuring the mass andvolume of the sample. The results of theexperiment are:

mass of sample (m) 155.65 gvolume of sample (V) 7.50 cm3

(a) Calculate the density of the platinum

sample using this data.(b) Chemical data books list the densityof pure platinum as 21.4 g/cm3. Is thesample of platinum pure?

(c) Use the periodic table to identify thesymbol for platinum.

(d) Use the periodic table to classifyplatinum as a metal, semi-metal ornon-metal.

5. A sample of gallium was put in a test tubeand heated in a beaker of warm water.A temperature probe connected to a data

logger was placed in the melted gallium tomonitor its temperature. The tube of meltedgallium was put in a test-tube rack andallowed to cool slowly. The data intable 2.7 was collected as the gallium cooled.

(a) Identify the dependent variable in thisexperiment.

(b) Plot a line graph of this data.(c) Identify the freezing point of this gallium

sample. Justify your answer.(d) Identify the melting point of this gallium

sample. Justify your answer.(e) Chemical data books list the melting

point of pure gallium as 30 C. Is thesample pure?

(f) Use the periodic table to classifygallium as a metal, semi-metal or non-metal.

6. Use the following data to classify eachelement as a metal, semi-metal ornon-metal.(a) Element Ais lustrous and silvery in

appearance, and it has a high electricalconductivity.

(b) Element Bcan be drawn into long, thinwires.

(c) Element Chas a low melting pointand shatters into tiny crystals whenhammered.

(d) Element Dhas a very high meltingpoint and is a semi-conductor ofelectricity

(e) Element Eis a gas at standardtemperature and pressure.

(f) Element Fhas a high thermalconductivity and is highly malleable.

7. Arsenic is a poisonous element; its symbolis As. Arsenic oxide can be used to killpests such as termites. Natural arsenicis an element that can exist in differentstructural forms known as allotropes. Theyellow form of arsenic exists as a tetratomicmolecule and is very volatile. It is unstableat 25 C and gradually changes to the greyform. The grey form is lustrous, very brittleand a good conductor of heat. The greyform is a poor electrical conductor whilethe yellow form is a non-conductor ofelectricity.(a) Identify the properties of arsenic that are

similar to those of metals.(b) Explain why arsenic is classified as a

semi-metal.

Table 2.7

Time (min) 0 1 2 3 4 5 6 7 8 9

Temperature (C) 36 34 32 31 30 30 30 29 28 26
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Chemical reactivity of elementsIf you place a crystal of sodium in water, it reacts violently and generates

considerable quantities of heat. A similar crystal of gold does not react

with water at all. These observations show that different elements havedifferent reactivities. Reactivity is a chemical property that is related to

the electronic structure of the element. Some elements, such as potassiumand fluorine, are highly reactive while others, such as argon, are inert.

u Unreactiveelements can exist as free elements in nature.

u Reactiveelements combine with other substances in the environment to

form compounds.

Metals such as caesium, potassium, calcium and magnesium are very

reactive elements. They readily combine with oxygen or water to form

compounds. In contrast, gold is very unreactive and is sometimes calleda noble metal. Gold reacts with other chemicals only under extreme con-

ditions. This explains why gold can be found as a free metal in the litho-

sphere. Such free metals are called native metals. Native iron is found asmeteoric iron, but it is usually alloyed with nickel. Platinum, palladium,

osmium, rhodium, ruthenium and iridium are often found together as

metallic alloys.

Figure 2.5

Sodium is very reactive and must

be stored in the absence

of water and air.

Of the non-metals, fluorine and oxygen are the most reactive andhelium and neon are the least reactive. Helium and neon are examples of

noble gases. All the noble gases exist as free elements in nature.

Although oxygen is reactive and forms many compounds, it also existsas a free element in the atmosphere due to the very low reactivity of nitro-

gen and argon gases. Other reactive elements can exist as free elements in

alloy:a mixture of a metal withone or more other elements(these other elements areusually metals)

Remember

Before beginning this section,you should be able to: identify internationally

recognised symbols forcommon elements.

Key content

By the end of this section, youshould be able to: explain the relationship

between the reactivity of anelement and the likelihood ofit existing as an uncombinedelement

account for the uses of metalsand non-metals in terms oftheir physical properties

plan and perform aninvestigation to examine someuses of a range of commonelements

analyse information fromsecondary sources todistinguish the physicalproperties of metals andnon-metals.


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nature if they are in environments that protect them from reaction. Thus,sulfur can be found in the lithosphere in vast subterranean ore bodies

because of its insolubility in water and its low reactivity with oxygen at lowtemperatures. Table 2.8 lists the elements that can exist free in nature.

Table 2.8Elements can exist free in nature or as alloys.

Exist separately as metals or as alloys with one another

Au Ag Hg Pt Pd Os Ir Rh Ru Fe

Exist separately as non-metals

He Ne Ar Kr Xe Rn N2 O2 S C

Metals can be ranked according to their chemical reactivity with other

materials such as oxygen, water and acids. This list is referred to as theactivity series. Table 2.9 lists the common metals in decreasing order of

reactivity.

Table 2.9 Activity series of some common metals

Most active Least active

K Na Ca Mg Al Zn Fe Pb Cu Hg Ag Au

Uses of elements

The uses of elements are directly related to their physical and chemicalproperties. For example, aluminium is a malleable metal that can be

readily formed into saucepans, window frames and thin foils for cooking.

Its high thermal conductivity allows rapid heat transfer to the food insaucepans or through foil. Its high tensile strength and reduced tendency

to corrode makes it an excellent building material.Table 2.10 lists some common elements and the properties that make

them useful in our society.

Table 2.10Uses and properties of some elements

Element Use Property related to use

copper electrical wiring ductility; high electrical

conductivity

iron structural building materials high tensile strength

zinc galvanising of iron high reactivity allows it to

preferentially corrode and protect

the iron

gold ornaments, jewellery lustre; highly unreactive

argon atmosphere for welding and

metallurgy

inert

helium meteorological balloons low density

silicon computer chips, transistors semi-conductor

Figure 2.6

Aluminium is a malleable metal. It canbe pressed and rolled

into sheets.

DATAANALYSIS

2.3

Properties and usesof elements


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48 THE CHEMICAL EARTH48 THE CHEMICAL EARTH

SUMMARY

u Elements are composed of small particles called atoms. Atoms canform larger aggregates called molecules.

u Elements cannot be physically separated or decomposed.

u Elements can be classified as metals, semi-metals or non-metalsaccording to their physical properties. These properties determinetheir use.

u Metals are shiny and conduct electricity.u Non-metals are dull and are electrical insulators.

u Semi-metals have some properties that are similar to metals andothers that are similar to non-metals.

u Unreactive elements can exist as free elements in nature.

u Reactive elements must be stored away from air or moisture.

u Reactive elements combine with other substances in theenvironment to form compounds.

2.2 QUESTIONS

1. Identify the metal that is used as a filament inincandescent light bulbs.

A IronB Magnesium

C TungstenD Gold

2. Identify the list that correctly places the metalsin increasing order of chemical reactivity.

A Iron, calcium, lead, goldB Silver, copper, iron, magnesiumC Copper, zinc, potassium, magnesiumD Potassium, zinc, iron, silver

3. Tungsten is a very useful metal. It can beobtained from the mineral wolframite, so issometimes called wolfram, which providesits symbol W. Wolframite is often found incombination with tin ores and, in the earlydays, this made the tungsten difficult toisolate. Tungsten requires considerable heatto melt; its melting point is 3410 C andboiling point is 5930 C. The metal was firstused as the filament in electric light bulbs in1913. Tungsten is classified as a heavy metal,along with gold and platinum. Its density is19.3 g/cm3; it has high tensile strength; itscarbide is exceptionally hard.

Identify the properties of tungsten that make itsuitable for use as (a) filaments in electric lightbulbs and (b) as a component of tool steel.

4. Titanium is used as a structural metal inaircraft and spacecraft. Identify from thefollowing list of properties those that makethis metal useful for aircraft and spacecraft. melting point 1660 C;

boiling point 3287 C density 4.50 g/cm3(compared with

7.86 g/cm3for iron and 2.70 g/cm3foraluminium)

electrical conductivity 2.3 MS/m(compared with 63 MS/m for silver)

thermal conductivity 22 J/s/m/K(compared with 237 J/s/m/K foraluminium)

high tensile strength

5. Match the use of the indicated element in thefirst column of table 2.11 to a property in thesecond column.

Table 2.11

Element and use Property

A. copper cooking pots 1. high electricalconductivity

B. lead roof sheeting 2. low corrosion

C. carbon (graphite) electrodes

3. high thermalconductivity

D. gold jewellery 4. soft and malleable

E. chromium stainlesssteel sinks

5. inert and lustrous

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2.1INVESTIGATING THE PHYSICAL

PROPERTIES OF ELEMENTS

AimTo collect first-hand data on the physical propertiesof some elements to classify them into groups

Safety issues

Wear safety glasses throughout this experiment.

Do not touch iodine crystals or breathe thevapours; examine them in a sealed tube.

Identify other safety issues relevant to thisexperiment by reading the method.

Materials samples (granules, wires, sheets) of zinc,

magnesium, iron, copper, lead, tin, aluminium,sulfur (melted and allowed to cool into lumps),red phosphorus, iodine, graphite (carbon) rods

1 cm cubes of various metals such as aluminium,zinc, iron, copper, lead and tin

DC power supply light bulb on stand electrical leads/clips ammeter

Petri dishes electronic balance 10 mL measuring cylinder

ball hammer

Method1. Appearance

For each element provided, describe its colourand state whether it is lustrous or dull.

2. Electrical conductivity

(a) Set up a simple electrical circuit as shownin figure 2.7 using a 12 V DC power supplyand electrical meters or lamps.

(b) Connect each element sample into thecircuit and measure the relative brightnessof the lamp (use a rating scale) or measurethe current on the ammeter/milliammeter).Record your observations in your logbook.

3. Density(Note:Weigh samples in a dish or on filterpaper.)

(a) Some metal samples are available as 1 cmcubes, so their volume is 1 cm3. Measuretheir mass on an electronic balance andcalculate their density.

(b) For solid samples that are irregular in shape,measure their mass on an electronic balanceand their volume by displacement of waterin a small measuring cylinder. Dry thesample after use.

4. Malleability and hardness

(a) Use a ball hammer to determine whetherthe solid samples deform or shatter whenstruck. (Note: Iodine should be tested onlyin a fume hood, using only one crystal.)

(b) Identify which samples are ductile byfinding out whether they are availableas wires.

(c) Identify which samples are malleable byfinding out whether they are availableas sheets.

Results and analysis1. Tabulate your collected data.

2. Examine the data and classify the elementsamples as metals or non-metals. Construct atable to show your classification.

3. Justify the classifications you made in 2.

4. Rank the metals in order of decreasing density.

ConclusionWrite a brief conclusion for this experiment.

PRACTICALACTIVITIES

PRACTICALACTIVITIES

Figure 2.7

Circuit for testing electrical conductivity

DC power supply

02 V

+

+

Sample

Switch

Ammeter/milliammeter

( orlamp)


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2.2CLASSIFYING ELEMENTS

AimTo use second-hand data to classify elements as:

(a) solids, liquids or gases

(b) metals, non-metals or semi-metals

Materials

2 copies of the periodic table coloured pencils or highlighters

Part A: Solids, liquids and gasesMost elements are solids so we will process data foronly selected elements to determine whether theyare solids, liquids or gases. Table 2.12 provides themelting and boiling points of selected elements.

Table 2.12

Element

symbol

Melting

point (C)

Boiling

point (C)

State (solid,

liquid or gas)

He 272 269

Li 180 1342

O 219 183

F 220 188

Ne 249 246

S 113 445

Cl 101 34

Ar 189 186

Se 217 685

Br 7 59

Kr 157 152

I 114 184

Xe 112 108

Rn 71 62

1. Copy table 2.12 into your workbook.

2. Use the data in table 2.12 and the following rulesto determine whether the selected elements aresolids, liquids or gases, and complete the lastcolumn of the table.

An element is a solid if its melting point isgreater than 25 C.

u An element is a liquid if its melting point is lessthan 25 C and its boiling point is greater than25 C.

u An element is a gas if its boiling point is lessthan 25 C.

3. Hydrogen and nitrogen are gases; mercury is aliquid. All other elements, apart from those listedin the table, are solids.

4. Label a copy of the periodic table, Solids, liquidsand gases.

(a) Select a colour (such as green) to representsolids. Colour all the elements of the periodictable that are solids with this colour.

(b) Choose a second colour (such as blue) forliquids. Colour all the elements that areliquids with this colour.

(c) Choose a third colour (such as violet) for

gases. Colour all the elements that are gaseswith this colour.

Part B: Metals, non-metals and

semi-metalsMost elements are metals and so we will processdata for only selected elements.

1. Use the following clues to classify and list theseelements as metals, non-metals or semi-metals.

All the gaseous elements listed in table 2.13 arenon-metals.

Six of the seven semi-metals have the followingatomic weights: 10.81, 28.09, 72.59, 74.92,121.75, 127.6.

Element 85 is a semi-metal.

Bromine is a fuming, red-brown liquid.

Carbon is brittle in its graphite form and anon-conductor in its diamond form.

2. Copy and complete table 2.13 in your workbook.The elements listed in the table are metalsif their electrical conductivity is greater than0.1 MS/m; otherwise they are non-metals.

DATAANALYSIS

DATAANALYSIS


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Table 2.13

Element

symbol

Electrical

conductivity (MS/m)

Metal or

non-metal

P 1015

S 1021

Ga 3.9

Se 104

I 1013

Hg 1.0

3. Apart from the elements mentioned in 1 and 2above, all other elements are metals.

4. Label a copy of the periodic table, Metals,non-metals and semi-metals.

(a) Select a colour (such as red) to representmetals. Colour all the elements of theperiodic table that are metals with this colour.

(b) Choose a second colour (such as orange) forsemi-metals. Colour all the elements that aresemi-metals with this colour.

(c) Choose a third colour (such as yellow) fornon-metals. Colour all the elements that are

non-metals with this colour.

General questions

1. Identify the location of gaseous elements in theperiodic table.

2. Identify the location of non-metallic elements inthe periodic table.

3. Describe the location of semi-metals in theperiodic table in relation to the metals andnon-metals.

2.3PROPERTIES AND USES

OF ELEMENTS

Table 2.14 lists some common elements and theiruses. Examine each of these and complete the tableby selecting all of the following properties that arerelated to each use.

(a) ductility

(b) malleability

(c) low reactivity

(d) low adherence to other materials suchas glass

(e) high lustre and reflectivity

(f) low melting point

(g) high electrical conductivity

(h) high density

(i) uniform expansion rate on heating

Table 2.14

Element Use

Properties related

to use (a) (i)

silver mirrors

mercury thermometers

tin plating of steel

lead soldering(lead alloy)

lead sinkers

(for fishing)

aluminium high voltagecables and wires

nickel coinage

chromium plating of steeland copper

DATAANALYSIS

DATAANALYSIS

Core Science Chapter 2

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