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Topic 1 - Planet Earth The atmosphere Components

% by volume

Nitrogen, N2(g)

78%

Uses

for food packaging

(成份)

Oxygen, O2(g)

21%

Components & Uses

for welding metals

Noble gases He(g), Ne(g), Ar(g)

*Carbon dioxide, CO2(g)

0.03%

Water vapour, H2O(g)

variable

Industrial method: (工業上)

supporting burning of fuels

0.9% He(g): filling airship

Ne(g): advertising lights

Ar(g): filling light bulb

fractional distillation (分餾法) of liquid air

because different components have different boiling points Separation method

as a refrigerant

Smaller molecular mass Lower boiling point

*Since % by volume of CO2(g) in the air is too small, we will not obtain it from the air industrially. Air is purified and liquefied (by cool down to -200oC)

Oxygen gas can

Larger molecular mass Higher boiling point

relight a glowing splint.

Test for components

Ch2 The atmosphere / Ch3 Oceans / Ch4 Rocks and minerals www.hksciblog.edublogs.org/dse-chem

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Topic 1 - Planet Earth 1. Which of the following substances is the most abundant in dry air? A. Oxygen B. Nitrogen C. Carbon dioxide D. Water vapour

2. Excluding water vapour, the volume of argon, carbon dioxide, nitrogen and oxygen in the atmosphere can be arranged in a descending order as A. oxygen, nitrogen, carbon dioxide, argon. B. nitrogen, oxygen, argon, carbon dioxide. C. argon, carbon dioxide, nitrogen, oxygen. D. oxygen, argon, carbon dioxide, nitrogen.

3. Which of the following statements about air is correct? A. Nitrogen can be obtained from fractional distillation of atmospheric air. B. Chlorine gas can be obtained by fractional distillation of liquefied air. C. Argon is one of the components of air. D. Air is the only component of atmosphere.

4. Which of the following methods can be used to separate oxygen and nitrogen from liquefied air? A. Filtration B. Crystallization C. Sublimation D. Fractional distillation

5. Oxygen and nitrogen can be separated from liquefied air by fractional distillation since they have different A. densities. B. melting points. C. boiling points. D. chemical properties.

6. Which of the following substances could NOT be obtained through fractional distillation of liquid air? A. Oxygen B. Carbon monoxide C. Nitrogen D. Krypton

7. Mercury(II) oxide is decomposed on heating according to the following reaction. Mercury(II) oxide  Element X + Gas Y Gas Y can A. turn limewater milky. B. turn moist blue litmus paper red. C. relight a glowing splint. D. give a ‘pop’ sound with a burning splint.

8. Which of the following reactions involve oxygen gas? (1) ‘Pop’ sound test of hydrogen (2) Burning of petrol in car engine (3) Corrosion of sodium metal A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3)

9. The steps to separate nitrogen and oxygen from air are listed below but are in a wrong sequence. (1) Air is liquefied by repeated cooling and compression. (2) Nitrogen boils off as gas. (3) Oxygen boils off as gas. (4) Liquid air is warmed up bit by bit.

10. Nitrogen is very useful (1) in food packaging to prevent unwanted reactions caused by air. (2) as a refrigerant for storing things at a very low temperature. (3) in making ammonia for further production of fertilizers. A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3)

Which of the following steps show the correct sequence? A. (1)  (4)  (2)  (3) B. (4)  (2)  (3)  (1) C. (1)  (4)  (3)  (2) D. (4)  (3)  (2)  (1)

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Topic 1 - Planet Earth

.

element

.

compound

. . .

mixture

a mixture of elements

a mixture of compounds

a mixture of compounds and elements

. . .

Element is the simplest form of substance which cannot 元素 be further divided. Compound is a substance made up of two or more elements 化合物 chemically joined together Mixture is a substance made up of two or more substances 混合物 mixed together without any chemical reaction.

11. Air is A. an element. B. a compound. C. a mixture of elements. D. a mixture of compounds and elements.

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Topic 1 - Planet Earth [10CE/MC#6] 12.

[05CE/MC#3] 13. The table below gives some information about certain components in a sample of liquefied air. Boiling point/oC -186 -196 -183

Component argon nitrogen oxygen

In what order are these components distilled out when the sample undergoes fractional distillation? A. B. C. D.

nitrogen, oxygen, argon nitrogen, argon, oxygen oxygen, argon, nitrogen oxygen, nitrogen, argon

The ocean: seawater is a ___________ of water , salts and dissolved gases

Components

Components

Percentage by mass

Water

96.5

Sodium chloride

2.4

Magnesium chloride

0.5

Sodium sulphate

0.4

Calcium chloride

0.1

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Topic 1 - Planet Earth Separate out the common salt from sea water Step 1: filtration (過濾法)

Separate out the pure water from sea water Simple distillation (簡單蒸餾法) By Quickfit apparatus:

Separation method

Step 2: evaporation (蒸發)

(Physical method)

Safety precaution: 1. Anti-bumping granules are added to ensure smooth boiling. 2. The end of the delivery tube should be placed above the distillate. To prevent sucking back of cold distillate into the hot boiling tube. The boiling tube may crack. Or by simple apparatus:

* The sodium chloride obtained by the above method is in powder form and may contain some impurities, e.g. other minerals in sea water. (To obtain pure NaCl(s): crystallization)

Test for sodium ions: ‘flame test’ Na+ salt Golden yellow flame + Lilac flame K salt Brick-red flame Ca2+salt Bluish-green flame Cu2+salt

Test for chloride ions: ‘add *acidified silver nitrate solution’ Ag+(aq) + Cl-(aq)  AgCl(s) white precipitate is formed * Acidified by dil. HNO3(aq): to prevent formation of other white insoluble compounds (e.g. silver carbonate and silver sulphite)

Test for components 1. A clean platinum wire is dipped into concentrated hydrochloric acid. 2. It is then dipped into powdered sodium chloride. 3. The wire is heated in non-luminous flame.

Test for water: Turn dry cobalt chloride paper from blue to pink. Or turn anhydrous copper(II) sulphate from white to blue.

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Topic 1 - Planet Earth How to obtain a pure sodium chloride solid from sea water? 

Pure sodium chloride crystals can be obtained from a saturated solution of sea water by crystallization: i)

Warm the filtrated sea water in an evaporating dish until a saturated solution is obtained.

ii)

Cool the solution slowly. Large sodium chloride crystals are obtained.

iii)

Filter off the crystals. Wash them with small amount of cold water and dry them with filter paper.

growing sodium chloride crystals 

A saturated solution is a solution containing the maximum amount of solute (sodium chloride) at a certain temperature.

Small crystals are obtained if the solution is cooled quickly.

Filtration can be employed to separate a solute from a solution.

What can we obtain from sea water using a chemical method – electrolysis (電解) Electrolysis of sea water to produce hydrogen gas, chlorine gas and sodium hydroxide solution:

brine = sea water

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Topic 1 - Planet Earth 1. Which of the following substances can be found in a sample of sea water? (1) Sodium chloride (2) Calcium chloride (3) Magnesium chloride A. (1) and (2)only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3)

2. Which of the following purposes of crystallization is correct? A. To separate an insoluble solid from a liquid. B. To obtain water from an aqueous solution. C. To purify solids. D. To purify the solution.

3. Which of the following methods can be used to remove the insoluble impurities, such as mud, from a sample of sea water? A. Evaporation B. Filtration C. Crystallization D. Electrolysis

4. Which of the following statements about filtration is correct? A. It can separate a soluble solute from its solution. B. The solid left on the filter paper after filtration is called residue. C. The substance to be filtered is called filtrate. D. Filtration is an effective way to purify a solid.

5. A large amount of sodium chloride is found in sea water. Which of the following methods can be used to extract pure water from sea water? A. Filtration B. Distillation C. Crystallization D. Sublimation

6. Anti-bumping granules are added in the set-up of distillation. This is to ensure that (1) substances evaporate at their corresponding boiling points. (2) higher purity of distillate can be obtained. (3) cooling effect is better. A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only

7. Which of the following statements is correct? (1) Sodium chloride is the most abundant mineral in sea water. (2) Pure sodium chloride could be removed from sea water by distillation. (3) The composition of sodium chloride in sea water may vary slightly according to the location and depth of the sea. A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3)

8. The element sodium is usually found in fireworks, since A. sodium is an essential substance to ignite fireworks. B. sodium burns with a golden yellow flame. C. sodium makes fireworks explode violently. D. burning sodium gives the sound of explosion.

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Topic 1 - Planet Earth 9. Which of the following combinations about the flame colours of metals is INCORRECT? A. B. C. D.

Metal Calcium Sodium Potassium Copper

Flame colour Brick-red Golden yellow Orange Bluish green

When acidified silver nitrate solution is added to magnesium chloride solution, a white precipitate is formed. The white precipitate is A. magnesium nitrate. B. silver chloride. C. silver metal. D. magnesium metal.

11. Chlorine is a product from the electrolysis of sea water. Which of the following is/are the use(s) of it? (1) To make bleach (2) To make fertilizers (3) To kill germs A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only

10. Which of the following statements is INCORRECT? (1) If a sample turns dry cobalt chloride paper pink, the sample is pure water. (2) If a sample contains chloride ions, effervescence occurs when excess dilute nitric acid and silver nitrate is added to the sample. (3) In a flame test, dilute hydrochloric acid is used to moisten the platinum wire. A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3)

12. Hydrogen is a product from electrolysis of sea water. Which of the following are the uses of hydrogen What are the main products of electrolysis of sea water? A. Sodium and chlorine B. Sodium hydroxide and chlorine C. Sodium, chlorine and hydrogen D. Sodium hydroxide, chlorine and hydrogen

[10CE/MC#16] 13.

[05CE/MC#5] 14. When a flame test is performed on copper(II) chloride, what is the colour of the flame observed ? A. B. C. D.

golden yellow pale purple brick-red bluish-green Ch2 The atmosphere / Ch3 Oceans / Ch4 Rocks and minerals

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Topic 1 - Planet Earth 15. Name the method and draw a labelled diagram for the following experimental set-ups: (a)

Removing insoluble impurities from sea water:

_______________________

(b)

Obtaining salts in solid form from sea water:

_______________________

(c)

Obtaining pure water from sea water:

_______________________

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Topic 1 - Planet Earth The rocks: mixture of minerals: a naturally occurring substance (element or compound) with definite chemical composition) An ore (磺 石) is a rock containing the mineral from which a particular metal in form of oxides, carbonates and chlorides, etc. Ore Metal in the ore Uses Bauxite Aluminum Materials for construction Copper pyrite, malachite Copper Making floor Cement Limestone Calcium Glass Materials for construction Haematite Iron

Components Limestone, chalk and marble & uses Limestone (石灰石), chalk (白堊) and marble (大理石) are three common materials in the Earth's crust. They are different forms of calcium carbonate: (softest) (hardest)

The main steps involved in getting a metal from its ore: i)

Mining of the ore (digging the ore from the ground)

ii)

Separation of the useful mineral from waste

iii)

Extraction of the metal from the mineral, e.g. 

Physical separation such as panning for gold

Heating alone

Heating the ore with carbon (carbon reduction)

Electrolysis of molten ore

Separation method

iv)

Purification of the impure metal Ch2 The atmosphere / Ch3 Oceans / Ch4 Rocks and minerals

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Topic 1 - Planet Earth Action of water, acid and heat on calcium carbonate 

Action of water 

Calcium carbonate is i________________ in water.

Action of acid 

Calcium carbonate reacts with dilute hydrochloric acid to give calcium chloride, water and carbon dioxide: CaCO3(s) + 2HCl(aq)  ___________________________________ Word equation:

______________________________________________

Observation:  Calcium carbonate dissolves to give a c______________ solution.  E_________________ (bubbles of carbon dioxide are evolved) occurs.

Action of heat 

Calcium carbonate decomposes on heating to give c_________ o_________ (quicklime or lime) and carbon dioxide: CaCO3(s)

 _______________________ [Q___________ (生石灰)]

Word equation:

______________________________________________

When calcium oxide is added to water, heat is released and c___________ h____________ (slaked lime) is formed: CaO(s) + H2O(l)  ___________________ [S_________ l_______ (熟石灰)] Word equation:

______________________________________________

Calcium hydroxide is slightly soluble in water. The saturated calcium hydroxide solution formed is called limewater. water + Ca(OH)2(s)  ____________________ (l_______ w________) Word equation:

______________________________________________

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Topic 1 - Planet Earth Tests for calcium and carbonate in calcium carbonate 

Calcium compounds give a b_______ r______ f_______ in the flame test.

Carbonate can be tested by adding dilute hydrochloric acid to the calcium carbonate. The gas evolved (carbon dioxide) turns limewater milky due to formation of insoluble calcium carbonate: Ca(OH)2(aq) + CO2(g)  ________________________ (Milky)

Chemical reactions involving CaCO3, CaO and Ca(OH)2

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Topic 1 - Planet Earth 1. Minerals are any substances A. found or obtained by mining. B. that can be absorbed by human bodies. C. formed by chemical reactions. D. any solid elements or compounds that occur naturally in the ground.

2. Which of the following is the most abundant element found in the Earth’s crust? A. Oxygen B. Nitrogen C. Aluminium D. Silicon

3. Arrange the procedures of obtaining metals from its ores in a correct sequence: (1) Increasing ore concentration (2) Metal extraction (3) Digging up ores (4) Purifying metal A. (1)(4)(3)(2) B. (3)(1)(2)(4) C. (2)(3)(4)(1) D. (1)(3)(2)(4)

4. Haematite contains A. little iron and a lot of copper. B. a lot of iron and copper(II) oxide. C. a lot of iron metal. D. a lot of iron(III) oxide.

5. The second most abundant metal in the Earth’s crust is A. iron. B. copper. C. aluminium. D. gold.

6. Aluminium can be extracted by A. filtration of its ores. B. fractional distillation of its molten ores. C. electrolysis of its molten ores. D. sublimation of its molten ores.

7. Which of the following combinations about the extraction of metals is correct?

8. Which of the following word equations shows correctly the reaction that occurs when calcium carbonate is heated strongly in air? A. calcium carbonate  calcium oxide + carbon B. calcium carbonate  calcium + carbon + oxygen C. calcium carbonate  calcium oxide + carbon dioxide D. calcium carbonate  calcium + carbon dioxide

A. B. C. D.

Metal to be extracted Calcium Aluminium Iron Copper

Method of metal extraction Heating with carbon Electrolysis of its molten ore Direct heating Heating with carbon

9. Limewater is a saturated solution of A. calcium carbonate. B. calcium oxide. C. calcium hydrogencarbonate. D. calcium hydroxide.

10. When dilute nitric acid is added to a sample of chalk, which of the following statements is INCORRECT? (1) The gas produced could give a ‘pop’ sound with a burning splint. (2) Calcium chloride is produced. (3) One of the compounds produced would give a golden yellow flame in a flame test. A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3)

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Topic 1 - Planet Earth [06CE/MC#25] 11. Which of the following substances contain calcium carbonate as the main chemical constituent? (1) (2) (3)

limestone chalk marble

A. B. C. D.

(1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3)

[10CE/MC#21] 12.

[08CE/MC#42] 13. Calcium carbonate can be obtained from quicklime through two processes as shown below.

Process 1

Process 2 calcium carbonate

limewater

quicklime

Which of the following combinations is correct?

A. B. C. D.

Process 1

Process 2

adding water adding Na2CO3(aq) adding water heating

adding Na2CO3(aq) adding water heating adding water

[04CE/MC#11] 14. A white solid is found around the mouth of a reagent bottle containing lime water. The white solid is likely to be A. B. C. D.

calcium oxide. calcium sulphate. calcium carbonate. calcium hydrogencarbonate. Ch2 The atmosphere / Ch3 Oceans / Ch4 Rocks and minerals

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Topic 1 - Planet Earth Answer: The atmosphere 1. B 9. A

2. B 10. D

3. C 11. D

4. D

5. C

6. B

7. C

8. D

The ocean 1. D 8. B 15.

2. C 9. B

3. B 10. D

4. B 11. C

(a)

5. B 12. D

6. B

7. B

6. C

7. B

(b)

(c)

The rocks 1. D 8. C

2. A 9. D

3. B 10. D

4. D

5. A

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Topic 1 planet earth