Part I Planet Earth/P.1
Part I: PLANET EARTH
I. Introducing Chemistry
A. What is Chemistry
a. The world around us is made of matter 物質.
b. Matter is anything that occupies space and has mass.
c. Chemistry is the study of matter, about their compositions, structures, properties and the changes among
them.
B. Chemistry in Our Lives Today
1. Clothing
Synthetic textile fibres, such as polyester 聚酯 and nylon 尼龍 (the products of petroleum)
2. Food
Fertilizers and insecticides increase world production of food. Food additives improve the taste,
colour of food.
3. Building materials
Building materials like metals, alloys 合金, glass and cement 水泥 come from the chemical
industry.
4. Transport
Fuels of cars, aircraft and ships come from the petrochemical industry 石化工業. Aeroplanes are
made of light and strong alloys.
5. Medical care
Drugs for curing diseases. Anesthetics 麻醉劑 and antiseptics 消毒劑 for surgeries.
Part I Planet Earth/P.2
II. Laboratory Safety
A. Basic Laboratory Safety Rules
1. Do not enter the laboratory unless a teacher is present.
2. Do not run or play in the laboratory.
3. Do not touch chemicals with bare hands. Use a spatula 刮勺 to transfer solid chemicals.
4. Do not leave experiments unattended.
5. Do not smell gases directly – wave the gas towards your nose.
6. Do not look directly down the test tube or point the mouth of the test tube towards anyone when
holding a test tube for heating.
7. Do not taste anything in the laboratory.
8. Do not eat or drink in the laboratory.
9. Do not put solid substances into the sink. Put them into appropriate waste bottles.
10. Wear safety glasses 安全眼鏡 whenever necessary.
11. Always handle flammable substances with great care and keep them away from flames.
12. Report all accidents and breakages to your teacher. If any chemical get onto your skin or clothing,
wash the affected area with plenty of water.
13. Always adjust the Bunsen burner to give a luminous flame when it is not in use.
14. Always tie up your tie or long hair.
15. Always wash your hands thoroughly after experiments.
B. Safety Precautions
a. Personal Protection
Part I Planet Earth/P.3
1. wear a laboratory coat 實驗袍 if possible.
2. wear safety glasses 安全眼鏡 whenever doing experiments.
3. wear rubber gloves 膠手套 when handling corrosive chemicals.
4. tie up long hair or ties while doing experiments.
5. wash hands before leaving laboratories.
b. Avoid Fire and Burns
1. never place a flammable liquid near a naked flame.
2. heat flammable liquids with a water-bath, a steam-bath, an oil-bath or an electrical heating mantle.
3. place hot objects on a heat-proof mat, not directly on the bench.
4. when you have no immediate use of Bunsen burner, turn it off, or turn it to a small luminous flame
光焰.
5. never look down heated test tubes or point them at any person.
6. be familiar with the location of first aid materials, sand bucket, fire extinguisher, fire blanket and
eye-wash bottle.
c. Avoid Chemical Hazards
1. do not eat or drink in the laboratory.
2. never taste any chemical or solution.
3. use the fume cupboard 煙櫥 for experiments involving toxic gases.
C. Hazard Warning Labels 危險警告標籤
Chemicals may be hazardous because they are corrosive, flammable or toxic. All bottles containing
hazardous chemicals should bear the appropriate hazard warning labels. This gives warning to
laboratory users and thus can minimize accidents
Part I Planet Earth/P.4
Type of hazardous
Hazardous nature
chemicals
Examples
concentrated hydrochloric acid,
damaging living tissue upon contact
concentrated sodium hydroxide
solution
causing serious risk to health and even
death if swallowed, breathed in or
chlorine, bromine
absorbed through the skin
exploding if ignited in air or exposed to
heat
catch fire easily
causing cancer or suspected of causing
cancer
ammonium nitrate
hydrogen, ethanol
trichloromethane
Part I Planet Earth/P.5
Type of hazardous
Hazardous nature
chemicals
causing
HARMFUL 有 害
IRRITANT 刺激性
limited
health
Examples
risk
if
swallowed, breathed in or absorbed
Iodine,
through the skin or causing reddening
dilute hydrochloric acid,
or blistering(使生水泡) of the skin
dilute sodium hydroxide solution
Part I Planet Earth/P.6
III. Common Apparatus and Equipments in the Laboratory
Beaker
Test tube
Test tube rack
Test tube holder
Test tube brush
Boiling tube
Stopper
Thermometer
Spatula
Dropper
Filter funnel
Measuring cylinder
Glass rod
Evaporating dish
Watch glass
Part I Planet Earth/P.7
Wire gauze
Heat resistant mat
Tripod
Bunsen burner
Crucible (with lid)
Crucible tongs
Clamp
Stand
Clamp and stand
Mortar and pestle
Reagent bottle
Dropping bottle
Conical flask
Flat-bottomed flask
Round-bottomed flask
Part I Planet Earth/P.8
Water trough
Desiccator
Gas syringe
Gas jar
Wash bottle
Electronic balance
Separating funnel
Dropping funnel
(Thistle funnel)
(Tap funnel)
Pipette
Burette
Volumetric flask
Part I Planet Earth/P.9
Pipette filler
Safety glasses
Fire blanket
Eye wash bottle
Fire extinguisher
Part I Planet Earth/P.10
IV. Physical Change and Chemistry Change
A. Physical Change
A Physical Change is a change in which no new substances are formed.
e.g. sublimation 昇華 of dry ice
e.g. dissolving sugar in water; boiling of water etc.
B. Chemical Change
A Chemical Change is a change in which one or more new substances are formed.
e.g.
burning of wax is a chemical change as new substances (e.g. carbon dioxide, water vapour) are
formed.
Classwork
State whether each of the following is a physical change or a chemical change. Give your reasons.
a. A wooden splint burns in air
b. Sugar dissolves in water
c. Water changes to ice in a freezer
d. Iron rusts
C. Properties of Substances
1. Physical Properties
Physical Properties of a substance are those properties that can be determined without the substance
changing into another substance.
e.g.
appearance (colour and physical state)
odour (smell)
taste
hardness
density
solubility (in various solvents)
malleability (金屬的)展延性 (ability to be rolled into sheets),
ductility 延展性(ability to be drawn into wires), electrical conductivity and thermal conductivity.
Part I Planet Earth/P.11
2. Chemical Properties
Chemical Properties of a substance are the chemical reactions of a substance, and the respective
conditions under which each reaction takes place.
e.g.
a piece of sodium will tarnish in air (reactive towards air),
can react vigorously when dropped into water (reactive towards water).
Example
a. Explain why “boiling point” is regarded as a physical property. Illustrate your answer by using water as
an example.
b. What is the boiling point of water at atmospheric pressure?
c. State three other physical properties of water.
d. State one chemical property of water.
Answer
a. We can determine the boiling point of water by heating water until it boils, and then measuring the
temperature of the boiling water. During the measurement, liquid water changes to steam, but no new
substance is formed.
b. 100oC
c. (I Water is a colourless liquid at room conditions.
(ii) Melting point of water = 0oC at 1 atmospheric pressure.
(iii) Density of water = 1 g cm-3 at room conditions.
d.
Water reacts with iron and air to form rust at room conditions.
Part I Planet Earth/P.12
V. Fundamentals of Chemistry
A.
Particle Theory
All matter is made up of Particles.
B. What are particles?
a. Particles are the tiny pieces of matter that make up everything in the world.
b. The word “particle” in science does not refer to particles like sand or chalk dust in our daily lives. It
refers to the smallest, most elementary unit of a substance.
C. Evidence that all matter is made up of particles
a. By Diffusion 擴散作用
Diffusion is the spreading and mixing of one substance into another, from a place of higher concentration
to a place of lower concentration.
b. Experiment and Explanation
Experiment
Explanation
Placing a potassium
Particles leave the crystal
permanganate
and mix through the
crystal in water
water particles
Placing a jar of air
upside down on a
jar of bromine
vapour
Bromine particles mix
through the air
particles
Part I Planet Earth/P.13
D. Elements in Nature
a. An element is a pure substance that cannot be broken down into anything simpler by chemical methods.
e.g. oxygen, carbon, sulphur, nitrogen, gold, silver, copper, iron, aluminium etc.
b. The most abundant elements in nature
Oxygen
49.9%
Silicon
26.0%
Aluminium
7.3%
E. Compounds
a. A compound is a pure substance made up of two or more elements chemically combined together.
Compound
Elements
Common salt (sodium chloride) NaCl
Sodium, chlorine
Water (H2O)
Hydrogen, oxygen
Carbon dioxide (CO2)
Carbon, oxygen
Glucose (C6H12O6)
Carbon, hydrogen, oxygen
Part I Planet Earth/P.14
b. Comparing properties of iron/sulphur mixture and iron(II) sulphate
(i) When we mix iron and sulphur together without heating, a mixture is formed.
(ii) When we heat iron and sulphur together, compound of iron(II) suphide is formed.
Property or Test
Appearance
Effect of magnet
Iron/sulphur mixture
Iron(II) sulphide
Yellowish black solid mixture
Dark brown solid
Only iron is attracted to the
Not attracted
magnet
Adding water
Iron sinks, most sulphur sinks but
Sinks as a single substance
some sulphur floats
Adding dilute hydrochloric
acid
Iron reacts with dilute
A gas with a bad egg smell is
hydrochloric acid to give
produced.
hydrogen
Iron and sulphur still retain their original properties in the mixture. However, when they combine to form
a compound, the compound shows new properties.
c.
Mixture
Composition by
mass
Variable
Fixed
(the substances in the mixture can be
(e.g. in water, the ratio by mass of
mixed together in any proportion)
hydrogen to oxygen is always 1:8)
Energy Change in Usually no heat change in making a
formation
mixture
Melting point and Melts or boils over a wide range of
boiling point
Compound
temperature
Heat is usually given out or absorbed
when a compound is made
Melts or boils at a definite temperature
(with a sharp m.p. or b.p.)
(does not have a sharp m.p. or b.p.)
General properties Each constituent substance retains its
Separation of
constituents
Properties are entirely different from those
own properties
of constituent elements
Constituents can be separated by
Constituent elements can only be separated
physical methods, based on
by chemical methods, not by physical
Part I Planet Earth/P.15
differences in physical properties
E. Classification of Matter
methods
Part I Planet Earth/P.16
VI. The Planet Earth
a. We all live on the Earth. The Earth’s crust, the ocean and the atmosphere provide us with all the
resources we need for our survival.
b. Some of the common resources we get from the Earth are:
1. coal, petroleum and natural gas for our energy needs.
2. metals such as the aluminium for making cooking utensils and soft drink cans;
3. sand and limestone for making glass and cement;
4. silicon for making compound chips.
A. The Atmosphere

The atmosphere is the layer of gases (Air) hundreds of kilomentres thick that surrounds the Earth.

Composition of air: oxygen O2 (21%)
nitrogen N2 (78%)
carbon dioxide CO2 (0.03% - 0.04%)
water vapour H2O (0.07%)
noble gases (0.9%)
a. Separation of oxygen and nitrogen from air
(i) The method used by industry to obtain oxygen and nitrogen from air is fractional distillation 分層
蒸餾法 of liquid air.
This method makes use of the different boiling points of oxygen (-183oC) and nitrogen (-196oC).
Part I Planet Earth/P.17
(ii) 3 stages in the fractional distillation of liquid air
1. Purification
Dust, water vapour and carbon dioxide are removed.
2. Liquefaction of air
The purified air is compressed and then cooled to -200oC.
3. Fractional distillation of liquid air

The liquid air is pumped into a fractional column and then allowed to warm up slowly.

Nitrogen boils at -196oC and oxygen boils at -183oC.
When liquid air warms up, liquid nitrogen becomes a gas first and is collected at the top of the
fractional column. Oxygen is collected from the lower part of the fractional column.
b. Uses of gases separated from air
(i) Oxygen
1. Oxygen is used in hospitals to help patients with breathing difficulties.
2. Liquid oxygen is carried on rockets and space shuttles to support the combustion of fuel.
3. Oxygen is used in cutting and welding 焊接 metals.
(ii) Nitrogen
1. Nitrogen is used in food packaging to prevent unwanted reactions caused by air.
2. As a refrigerant 致冷劑
3. To make ammonia (NH3) 氨
(iii) Carbon dioxide
1. As a refrigerant. Solid carbon dioxide (dry ice) is much colder than ice. It is used as refrigerant for
ice cream.
2. Many soft drinks are made by dissolving carbon dioxide under pressure in water.
3. Carbon dioxide is a dense and non-flammable gas. It is used in fire extinguishers to put out fire.
(iv) Noble gases
1. Helium is used to filled airships
2. Neon is used in advertising signs
3. Argon is used to fill light bulbs.
Part I Planet Earth/P.18
Example
The following table shows the information about the main gases present in air.
Gas
Percentage by volume in air
Boiling point (oC)
Argon
0.93
-186
Nitrogen
78
-196
Oxygen
21
-183
a.
What is the name of the process by which the components of air are separated?
b.
In what order are these components separated when the sample undergoes the process in (a)?
c.
Suggest ONE use of each of the components.
d.
Living things require oxygen for respiration. Fuels require oxygen for burning. Air contains much more
nitrogen than oxygen. Is it a good thing to have more oxygen than nitrogen in air? Explain your
reasoning.
Answer
a.
Fractional distillation of liquid air.
b.
nitrogen, argon, oxygen
c.
Argon: to fill light bulbs
Nitrogen: to make ammonia
Oxygen: To cut and weld metals
d.
No. If there were more oxygen in air, metals would be corroded faster. Things would also burn easier, so
there would be a greater hazard of fire.
c. Test for Oxygen and Nitrogen
(i) A simple test for oxygen is that it relights a glowing splint.
Part I Planet Earth/P.19
(ii) There is no simple test for nitrogen
d. Air quality in Hong Kong
Air quality in Hong Kong could be shown by the Air Pollution Index (API)空氣污染指數, which is
made by the Environmental Protection Department.
B. The Ocean
a. Sea water
Sea water is a water solution 溶液 of minerals and dissolved gases.
(i) A solution is made by dissolving solute in a solvent
i.e.
Solute (溶質) + Solvent (溶劑) = Solution (溶液)
(ii) Soluble substance
:
Insoluble substance :
A substance dissolves in solvent
A substance does not dissolve in solvent
A dilute (稀) solution contains small amount of solute in a given volume of solvent.
A concentrated (濃) solution contains a large amount of solute in a given volume of solvent.
A saturated (飽和) solution is a solution that has dissolved all the solute it can, at a given temperature.
Part I Planet Earth/P.20
b. Obtaining Common Salt from Muddy Sea Water
(i) Step 1: Filtration (過濾法)
There are millions of tiny holes in the filter paper.
The mud that remains on the filter paper is called the residue.
The sea water that passes through the filter paper and collects in the beaker is called the filtrate
(ii) Step 2: Evaporation (蒸發法)
A dilute solution becomes more concentrated and eventually becomes saturated.
(iii)
Step 3: Crystallization (結晶法)
Part I Planet Earth/P.21

As the water evaporates from a saturated solution, the solvent cannot hold all the solutes. The extra
solutes then separate out as crystals.

If the solution is evaporated quickly  small crystals
If the solution is evaporated slowly  large crystals

The crystals can be separated by filtration.
c. Obtaining Pure Water from Sea Water
(i) Distillation(蒸餾法) or Simple Distillation (簡單蒸餾法)
1. By Quick-fit apparatus
Part I Planet Earth/P.22
2. By test-tube scale apparatus
(ii) Condenser
: To cool the water vapour into liquid
Antibumping granules
: To ensure even boiling
Distillate
: The liquid collected by distillation
d. What does Common Salt contain
(i) Flame Test
1. When compounds of some metals are burnt in a Bunsen flame, different brightly coloured flames
will result. We can identify the metallic element in a compound by the flame colour produced. The
Part I Planet Earth/P.23
procedure is known as Flame Test.
Element in Compound
Flame Colour
Potassium
Purple (Lilac)
Sodium
Golden yellow
Calcium
Brick-red
Copper
Bluish-green
2. Procedures
(i) Moisten a platinum wire (or nichrome wire) with concentrated hydrochloric acid.
(ii) Heat the platinum wire strongly in a non-luminous flame.
(iii) Repeat step (i) and (ii) until no flame colour is seen.
(iv) Moisten the clean platinum wire with concentrated hydrochloric acid.
(v) Dip the wire into a crushed sample (or solution) of the substance to be tested.
(vi) Heat strongly in a non-luminous flame and observe the flame colour.
(ii) Test for chlorides – Silver nitrate Test (AgNO3)
Part I Planet Earth/P.24
The use of excess dilute nitric acid prevents formation of other precipitate e.g. silver carbonate and
silver sulphite, which are soluble in dilute nitric acid.
(iii) From the two chemical tests above, what does common salt contain?
Classwork
A and B are two unlabelled bottles. One of them contains potassium chloride solid while the other contains
sodium chloride solid. Suggest how you can distinguish between them.
Answer
Burn the two compounds in Bunsen flame separately. The one gives a purple (lilac) flame is potassium
chloride while the one gives a golden yellow flame is sodium chloride
e. Test for the presence of water in a sample
(i) Water turns blue cobalt(II) chloride paper pink. Thus we can test for the presence of water in a
sample using blue cobalt(II) chloride paper.
(ii) Water turns white anhydrous copper(II) sulphate blue.
Part I Planet Earth/P.25
f. Getting useful substances from sea water – By electrolysis 電解
(i) Electrolysis of Sea Water
When we pass electricity through sea water:
-chlorine gas (Cl2) is formed at the positive electrode
-hydrogen gas (H2) is formed at the negative electrode
-the sea water becomes sodium hydroxide solution (NaOH)

y  chlorine gas + hydrogen gas + sodium hydroxide solution
i.e. Sea Water electricit
g Salt Industry
Part I Planet Earth/P.26
Example
1. A student was given a glass of colourless liquid. He was asked to find out whether it was sea water by
testing the presence of sodium and chloride and water.
a. The student said he could taste the liquid to find out whether it was sea water. Do you think it was
suitable method? Why?
b. What is the name of the test to find out whether the liquid contained sodium ions?
c. Briefly describe a test to find whether the liquid contained chloride.
d. Suggest a test for the presence of water in the liquid.
Answer
a. It was not a suitable method because the liquid may be unclean, harmful or even poisonous.
b. Flame test
c. To show the presence of chloride, excess dilute nitric acid is added to the sample, and then silver
nitrate solution is added. If chloride is present, a white precipitate will be formed.
d. Add drops of the liquid into anhydrous copper(II) sulphate powder. If the white powder turns blue,
the liquid should contain water.
Part I Planet Earth/P.27
2. Electrolysis of sea water is an important industrial process.
a. What is the meaning of the term “electrolysis”?
b. Once sea water is electrolysed, what products can be obtained?
c. State TWO uses of each of the above products collected.
Answer
a. Electrolysis means “decomposition by electricity”.
b. Chlorine, hydrogen and sodium hydroxide.
c. Chlorine: manufacture of PVC / production of solvents / production of chlorine bleach / production
of hydrochloric acid / sterilization of drinking water and swimming pool water.
Hydrogen: production of margarine / acting as a rocket fuel / manufacture of ammonia / production
of hydrochloric acid.
Sodium hydroxide: Manufacture of soaps and detergents / production of chlorine bleach
Classwork
1. Complete the concept map using the following words:
(crystals, insoluble, saturated, soluble, solution)
Part I Planet Earth/P.28
2. Complete the concept map using the following words:
(bleach, hydrochloric acid, PVC, swimming pool water)
C. Rocks and Minerals
a. Metals in the Earth’s crust
(i) About 25% of the Earth’s crust consists of metals.
Only a few metals exist as free elements, e.g. silver and gold
Most metals exist as compounds in nature.
(ii) The chemicals that make up rocks are called Minerals 礦物.
e.g.
graphite and aluminium oxide are the most common minerals of rocks;
(iii) Rocks from which we obtained metals are called Ores 礦石.
Metal
Ore
Aluminium
Bauxite 鋁土礦
Copper
Copper pyrite 黃銅礦
Lead
Galena 方鉛礦
Iron
Haematite 赤鐵礦
b. The availability (and hence the price) of a metal depends mainly on
(i) the abundance of the metal in the Earth’s crust
Part I Planet Earth/P.29
(ii) the ease of mining its ore and the cost
(iii)the ease of extracting the metal from its ore and the cost
Part I Planet Earth/P.30
c. Extraction Metals from Their Ores
(i) Physical Methods
Only metals which exist as free elements can be extracted by physical methods. These metals include
gold and silver.
e.g. panning of gold 淘金
(ii) Heating the ore alone
We can extract mercury from cinnabar 硃砂 by heating it in air
(iii) Heating the ore with carbon
We can extract iron from haematite by heating it with carbon in a blast furnace 鼓風爐
(iv) Electrolysis of the molten ore
We can extract sodium, magnesium and aluminium by electrolyzing their molten ores.
Major Sources (Ore) and the Methods Used to Extract the Metal
Metal
Potassium
Ores
Method of Extraction
KCl in deposits and sea water
Sodium
common salt NaCl
Calcium
limestone CaCO3
Magnesium
magnesite MgCO3
Aluminium
bauxite
electrolysis of molten ores
heat in air
Zinc
zinc blende ZnS
Iron
haemitite Fe2O3
 oxide
sulphide  
then
Lead
galena PbS
oxide   metal
Copper
copper pyrite CuFeS2
Mercury
cinnabar HgS
heating with charcoal
heat in air
 metal
sulphide  
Part I Planet Earth/P.31
Silver
silver glance Ag2S
or free in nature
Gold
mechanical separation
free in nature
c. Investigating Calcium Carbonate (CaCO3)
Limestone composes primarily of the mineral calcite 方解石. Calcite composes of calcium carbonate.
(i) Action of heat on calcium carbonate

Upon heating, calcium carbonate changes to a white powder called quicklime 生石灰 (calcium
oxide, CaO). Carbon dioxide (CO2) is also given off.
heat
Calcium carbonate  calcium oxide

+ carbon dioxide
If water is added to calcium oxide, calcium hydroxide Ca(OH)2 is formed
 calcium hydroxide
Calcium oxide + water 

Calcium hydroxide is often called slaked lime 熟石灰. It is slightly soluble in water. The solution
formed is called limewater 石灰水.

Limewater is used to test for carbon dioxide gas. Carbon dioxide gas turns limewater milky due
to the formation of insoluble white calcium carbonate.
 calcium carbonate + water
Carbon dioxide + calcium hydroxide 
If we pass an excess 過量 of carbon dioxide into the limewater, the white precipitate disappears.
This is because the precipitate redissolves to form soluble calcium hydrogencarbonate
Ca(HCO3)2.
 calcium hydrogencarbonate
Calcium carbonate + carbon dioxide + water 
Part I Planet Earth/P.32
Classwork
Complete the following concept map.
calcium carbonate
heat
carbon dioxide
+
water
+
carbon dioxide
(ii) Action of dilute acid on calcium carbonate
When calcium carbonate reacts with dilute hydrochloric acid (HCl), effervescence 泡騰 occurs.
Calcium chloride, water and carbon dioxide are formed.
 calcium chloride + water + carbon dioxide
Calcium carbonate + dilute hydrochloric acid 
Part I Planet Earth/P.33
(iii) Action of water on calcium carbonate
Calcium carbonate is insoluble in water.
d. Formation of Chalk 白堊, Limestone 石灰石 and Marble 大理石
(i) Calcium carbonate occurs naturally in three main forms: Chalk, Limestone and Marble.
(ii) Chalk is the softest. Limestone is harder than chalk. Marble is the hardest
(iii) When sea animals die, their skeletons or shells sink into the mud at the bottom of the oceans. These
skeletons and shells are made up of calcium carbonate.
Part I Planet Earth/P.34
(iv) Earth movements may also cause the layers to sink further. Higher pressure and heat cause the chalk to
turn into much harder limestone and marble.
e. Formation of Limestone Caves 石灰石岩洞
(i) Weathering: 風化作用
Solid rock is broken down into smaller pieces.
1. Physical weathering
Part I Planet Earth/P.35
Rock gets broken into fragments but it is not chemically changed.
e.g. Plant roots grow into cracks in rocks and slowly to break up the rocks.
In the winter, water in the cracks expands as it freezes and break up the rocks.
2. Chemical weathering
Rock is broken by chemical change.
e.g. Carbon dioxide dissolves in rainwater produces carbonic acid. The acid reacts with limestone,
forming calcium hydrogencarbonate which is carried away in solution.
(ii) Erosion: 侵蝕作用
The wearing away of surface materials and the movement of products of weathering from where they
formed to a different location.
(iii) Formation of Limestone caves
1. When rain falls, it reacts with carbon dioxide in the air to form carbonic acid 碳酸 H2CO3.
 carbonic acid
Water + carbon dioxide 
2. When carbonic acid comes into contact with underground limestone, they react to form soluble
calcium hydrogencarbonate.
 calcium hydrogencarbonate
Calcium carbonate + carbonic acid 
3. The underground limestone is gradually dissolved in this way over millions of years, creating
underground holes called limestone caves.
Classwork
Limestone, chalk and marble are three different natural forms of the same compound – calcium carbonate.
How can you show that these three substances all contain calcium ions and carbonate ions?
Part I Planet Earth/P.36
Answer
Burn the three substances in Bunsen flame separately (or perform Flame test on the three substances). They
all give brick red flame, therefore, they contain calcium ions.
Dilute hydrochloric acid is added to the three substance separately. They all give colourless gas bubbles
(carbon dioxide), therefore, they contain carbonate ions.