1.1
WHAT IS CHEMISTRY ABOUT?
WHAT IS
CHEMISTRY
ABOUT?
CHEMISTRY
Substances
Compositions
Structures
Properties
Changes
• Matter- It is anything that occupies spaces
and has mass.
• Substances - A particular type of matter.
(a simple form of matter)
IRON
A LITTLE HISTORY OF CHEMISTRY
Fire can change one thing to another
Alchemists
Cheap Metals
----->
Gold
Figure 1.2
"The alchemist", by
Sir William Fettes
Douglas, 1853
The Philosopher's Stone (fairy tale)
According to the alchemists, the key to changing lead into gold was the
Philosopher’s Stone. This wasn’t actually a stone but powder, of which
only a small quantity was required. It was believed the Philosopher’s
Stone was to be made from mercury purified through hundreds of different
processes.
If you can come up with a
way to change lead into gold,
you would soon become a
millionaire. However, none
of the alchemists became
rich man.
Robert Boyle (1627-1691), ‘The Father of Chemistry’
•
Hypothesized that matter consisted of atoms
•
Denied the Greek classical elements
(earth, fire, air, and water )
1.2 CHEMISTRY IN OUR LIVES TODAY
燒肉驗出致癌物二氯丙醇
07月 18日
燒肉皮脆肉香，令人垂涎欲滴，但測試市面三百多種食物，發現燒肉含致癌物質
「二氯丙醇」，中心指樣本含量輕微，對健康影響不大，但有學者質疑當局標準過
於寬鬆，指世 及 對毒性強烈的二氯丙醇是「零容忍」，絕不容食物含該有毒物
質。食物安全中心抽驗三百一十八個食物樣本，包括肉類、家禽及製品、穀類及其
製品、零食等，以了解製作食物過程生產的污染物「氯丙二醇」及「二氯丙醇」的
含量，並據千名中學生飲食習慣，評估市民從食物中攝取上述化合物情況。
食物安全中心顧問醫生何玉賢表示，於動物測試證實二氯丙醇會影響腎臟及肝臟功
能、是可損害基因的致癌物，但認為市民如果注意均衡飲食，二氯丙醇對人體健康
影響不大。測試亦顯示約一成食物樣本的氯丙二醇含量，較每日最高可容攝取量的
每公斤兩微克高，其中以即食紫菜的含量最高，每公斤達五十微克。以人體五十公
斤計算，即連續進食兩公斤才有風險。何玉賢指，氯丙二醇雖證實會影響動物腎臟
、中樞神經及男性生殖能力，但從膳食攝取的氯丙二醇不會影響健康。
Class practice 1.1
The photos below are some commodities or facilities
in our daily lives which are affected by or related to
chemistry. Write down the names of chemicals in
them. The first one has been down for you as an
example.
(a) Clothing
polyester, nylon,
dyes
(b)Food
(c) Housing
(d) Transport
(e) Medicines
(f) Amusement park
facilities
A 1.1
(b) fertilizers, insecticides, food additives
(c) metals, alloys, cement, glass, plastics
(d) metals, alloys, fuels, glass, plastics
(e) drugs, antibiotics, artificial hormones
(f) metals, alloys, cement, glass, plastics, semiconductors
1.6
OBSERVATION,
INTERPRETATION
PREDICTION IN CHEMISTRY
AND
OBSERVATION in chemistry includes four activities:
Seeing with eyes
Smelling with nose
Hearing with ears
Feeling with hands
1.5 Observation, interpretation and prediction
in chemistry
Figure 1.11 How many things can you note about a burning candle?
For all the experiments you will do in this course, try your best to:
1. Observe carefully
4. Draw conclusions
and make predictions
2. Report clearly
and accurately
3. Analyse and
interpret the results
Laboratory safety
Laboratory safety is of first importance
in any experimental work.
BASIC LABORATORY SAFETY RULES
(1) Do not work in the laboratory unless your
teacher is present.
(2) Follow strictly the instructions given by your
teacher.
(3) Never run around or play in the laboratory. Do
not leave your bench unless it is necessary.
(4) Dispose of solid waste (e.g. broken glass, filter
paper, copper turnings etc.) in the waste bin,
never in the sink.
(5) Clean up all the spillage (on the floor or bench)
at once. Clean up the bench after experiment.
(6) Report all accidents and breakages to your
teacher at once.
(7) In case any chemical gets into eyes, flush the
eyes with running cold water immediately for at
least three minutes.
(8) For chemical burns on skin, place the affected
area under slowly running cold water until the
pain fades.
(9) Take all necessary safety precautions.
A 1.7
x
1.7
HAZARDOUS CHEMICALS
CLASSIFICATION OF HAZARDOUS CHEMICALS
explosive
1.7 Hazardous chemicals
oxidizing
flammable
carcinogenic
toxic
harmful
i
corrosive
1.7 Hazardous chemicals
irritant
(c) Clamp
(a) Flat-bottomed flask
(d) Retort stand
(e) Conical flask
(b) Round-bottomed flask
1.8 Common chemical apparatus
(i) Crucible
(h) Tripod
(j) Pipeclay triangle
(g) Evaporating basin
(k) Bunsen burner
(l) Crucible
(f) Wire gauze
tongs
(m) Spatula
(n)
1.8 Common chemical apparatus
Heat-resistant mat
(q) Desiccator
(p) Mortar
(o) Pestle
1.8 Common chemical apparatus
(t) Test tube
(u) Boiling tube
(w) Reagent bottle
(s) Test tube rack
(r) Test tube holder
1.8 Common chemical apparatus
(v) Dropping bottle
(dd) Thermometer
(bb) Plastic washbottle
(z) Beaker
(aa) Funnel
(y) Measuring
cylinder
(gg) Separating
funnel
(x)
Gas syringe
(cc) Teat pipette
1.8 Common chemical apparatus
(ee) Watch glass
(ff) Glass rod
CHEMISTRY  CHEMICALS (MATTERS)
Salt
Sugar
Plastic
Paper
How to classify matter?
Element
Compound
Mixture
1. Of E &E
2. Of E&C
3. Of C&C
2.2
ELEMENTS IN NATURE
WHAT IS
AN ELEMENT?
An ELEMENT is a pure substance that
cannot be broken down into anything simpler
by chemical methods.
e.g Iron, Carbon, Oxygen
Are they elements?
• Water
• Carbon dioxide
• Sand (silicon dioxide)
PERCENTAGE BY MASS OF ELEMENTS IN NATURE
aluminium
__________
_______
silicon
iron 4.1%
8.1%
27.7%
calcium 3.2%
sodium 2.3%
potassium 2.3%
magnesium 2.1%
all other elements 2.8%
46.6%
_______
oxygen
2.2 Elements in nature
Figure 2.16 Percentage
abundance by mass of
elements in nature.
Oxygen
50% by
mass of
all elements
Most
abundant
element in
nature
Free
element &
compounds
Class practice 1.2
air
water
Sand
(silicon
dioxide)
Oxygen is present as a free element in air, and in combined forms
(compounds) in water and sand.
WHAT IS A
COMPOUND?
Are they elements?
• Water
• Carbon dioxide
• Sand (silicon dioxide)
• No. They are compounds.
• hydrogen + oxygen
• Carbon + oxygen
• Silicon +oxygen
Pure
substances
COMPOUNDS
Made up of
two or more
elements
Elements chemically
combined together
Salt
Sugar
Plastic
Paper
For example
Hydrogen
electrolysis
+
Oxygen
WATER
heating
Sodium Chloride
reads 'reacts with'
copper + chlorine
reactants
(reacting substances)
2.3 Compounds
reads 'to produce'
copper(II) chloride
products
(substance produced)
deflagrating
spoon
brown
brown
copper( c
copper(II)
hloride
chloride
chlorine
copper
powder
(a)
(b)
Figure 2.20 Combining copper and chlorine to form a new substance — the
compound copper(II) chloride.
(a)
(b)
Heating of copper powder to red hot in a deflagrating spoon.
Reaction of hot copper with chlorine to form brown copper(II) chloride solid.
How to classify matter?
Element
Compound
Mixture
1. Of E &E
2. Of E&C
3. Of C&C
An ELEMENT is a pure substance that cannot be broken down
into anything simpler by chemical methods.
e.g Iron, Carbon, Oxygen
An Compound is a pure substance made up of 2 or more
elements chemically combined together.
e.g Carbon dioxide, water
The compound is a product which is a new substance which is
different from its constituent elements!!
heating
Sodium Chloride
Are they elements?
• Water
• Carbon dioxide
• Sand (silicon dioxide)
• No. They are compounds.
• hydrogen + oxygen
• Carbon + oxygen
• Silicon +oxygen
Which is the most abundant element ?
Oxygen
Which is the most abundant metal ?
Aluminium
DECOMPOSITION OF COMPOUNDS
Element
A
A-B-C
decomposed by
heat or electricity
(electrolysis)
Element
B
Element
C
DECOMPOSITION OF WATER
H
H 2O
decomposed by
heat or electricity
(electrolysis)
O
H
glowing
splint
mercury(II)
oxide
(a)
mercury
vapour
Bunsen
flame
(b)
glowing
splint
relighted
by oxygen
(c)
Figure 2.21 Decomposition of mercury(II) oxide into mercury and oxygen by the
application of heat.
How to classify matter?
Element
Compound
Mixture
1. Of E &E
2. Of E&C
3. Of C&C
2.4
COMPOUNDS AND MIXTURES
WHAT IS A
MIXTURE?
2.4 Compounds and mixtures
Mixtures of
•
•
•
•
•
Hydrogen and oxygen
sugar and salt
water and sugar
Oxygen and nitrogen
Oxygen and carbon dioxide
•
•
•
•
•
E+E
C+ C
C+ C
E+ E
E+ C
=
2.4 Compounds and mixtures
Vinegar is a mixture. It contains mainly
water and ethanoic acid.
2.4 Compounds and mixtures
There are three kinds of mixtures:
Element
Element
Element Compound
Compound Compound
2.4 Compounds and mixtures
DIFFERENCES BETWEEN MIXTURES AND
COMPOUNDS (EXPT 1.1)
We can study the differences between a mixture and a
compound by comparing a mixture and the compound of iron and
sulphur.
Element
Element
Compound
Sulphur
Iron
Iron(II) sulphide
Compare Colour and Physical
State
Sulphur
Observation
Iron
Iron(II) sulphide
Action of dilute hydrochloric acid
Observation
Sulphur
Iron
Iron(II) sulphide
Testing with bar magnetic
Observation
Sulphur
Iron
Iron(II) sulphide
13.
• We can obtain a mixture of iron and
sulphur powder. It is not a compound. It is
because iron and sulphur still retain their
original properties in the mixture.
Property or test
Iron
Sulphur
Iron/sulphur mixture
Iron(II) sulphide
Appearance
Black solid
Yellow solid
Yellowish grey solid
Black solid
Action of
magnet
Attracted by
magnet
Not attracted
by magnet
Only iron attracted
by magnet
not attracted by
magnet
Action of water
Sinks
Most sulphur
sinks, while a
little floats
All iron and most
sulphur sink, while a
little sulphur floats
Sinks
Action of dilute
hydrochloric
acid
Liberates
hydrogen
gas
No reaction
Only iron reacts to
liberate hydrogen
gas
Gives toxic
hydrogen sulphide
gas (with smell of
bad eggs)
Structure
Figure 2.24 Separating a mixture of iron filings and sulphur powder. Iron is attracted
by the magnet, sulphur is not.
2.4 Compounds and mixtures
Mixture
Compound
1. Composition by mass
Variable (the substances in
the mixture can be mixed
together in any proportion)
Fixed (e.g. in water, the
ratio by mass of hydrogen
to oxygen is always 1:8)
2. Changes in formation
No chemical reaction
takes place; usually no
heat change in making a
mixture
A chemical reaction takes
place; heat is usually given
out or absorbed when a
compound is made
3. Melting point (m.p)
and boiling point
(b.p.)
Melts or boils over a wide
range of temperatures (i.e.
does not have a sharp m.p.
or b.p.)
Melts or boils at a definite
temperature (i.e. with a
sharp m.p. or b.p.)
4. General properties
Each constituent substance
retains its own properties
5. Separation of
constituents
Constituents can be
separated by physical
methods, based on
differences in physical
properties
Properties are entirely
different from those of
constituent elements
Constituent elements can
only be separated by
chemical methods, not by
physical methods
2.4 Compounds and mixtures
•
•
•
•
•
•
Element/Compound/Mixture?
Gold
Water
Sodium chloride solution
Air
Oxygen
Iron(II) suphide
• Element. Pure substance, can not be broken down by
chemical methods.
• Compound. Pure substance, can be broken down into
hydrogen and oxygen by chemical methods.
• Mixture. It consists of sodium chloride (c)and water
(c)which have not chemically combined.
• Mixture. It consists of nitrogen (e),oxygen (e) and other
gases which have not chemically combined.
• Element. Pure substance, can not be broken down by
chemical methods.
• Compound. Pure substance, can be broken down into
iron and sulphur by chemical methods.
How can we differentiate these 2 coins? Which
is made of gold? Which is made of copper?
Gold has a higher density.
Gold is softer.
Copper will slowly tarnish in air.
1.4
PROPERTIES OF SUBSTANCES
PHYSICAL PROPERTIES
Figure 1.31 Metals are
malleable, so they can be
hammered or rolled into
sheets.
1.10 Properties of substances
Figure 1.32 Copper is ductile, so it can be drawn into a wire.
1.10 Properties of substances
PHYSICAL PROPERTIES of a substance are those properties
that can be determined/tested without the substance changing
into another substance.
CHEMICAL PROPERTIES of a substance are the chemical
reactions of the substance, and the respective conditions under
which each reaction takes place.
Physical properties of oxygen
Chemical properties of oxygen
Physical properties of sulphur
Chemical properties of sulphur
PHYSICAL AND CHEMICAL CHANGES
A physical change is a change in which no
new substances are formed.
Fig. 1.22
Cutting a piece of
paper into two halves
is a physical change
as no new substances
are created.
PHYSICAL CHANGE
A PHYSICAL CHANGE is a change in which no new
substances are formed.
Ice
melting

freezing
water
boiling

water vapour
condensation
heat absorbed
heat given out
sublimation
solid
gas
deposition
liquid
Change of state is a common example of physical change.
evaporating basin
(cool surface)
water
iodine
solid
iodine solid
Figure 1.26
Iodine solid
sublimes to form vapour on
heating. When in contact with a
cool surface, the iodine vapour
changes back directly to iodine
solid, without passing through
the liquid state.
1.9 Physical and chemical changes
iodine
vapour
Bunsen flame
Chemical change
A chemical change is a change in which one
or more new substances are formed.
Fig. 1.25
Burning a piece of
paper is a chemical
change.
Class practice 1.5
CHEMICAL CHANGE
A CHEMICAL CHANGE is a change in which one or more new
substances are formed.
State whether each of the following is a physical change or a chemical change.
Give your reasons.
1. Tearing a piece of paper into pieces
2. Breaking a glass
3. Boiling water into steam
4. Melting ice into water
5. Burning A piece of paper
1.9 Physical and chemical changes
State whether each of the following is a physical change
or a chemical change. Give your reasons.
(a) A magnesium ribbon burns in air.
(b) Sugar dissolves in water.
(c) Water changes to ice in a freezer.
(d) Iron rusts.
1.9 Physical and chemical changes
A1.4
(a)
Chemical change
(b)
Physical change
(c)
Physical change
(d)
Chemical change
(b) and (c) are physical changes because no new substances are
formed.
(a) and (d) are chemical changes because new substances are
formed.
1.9 Physical and chemical changes
1.
2.
3.
4.
5.
What is chemistry about?
In what ways is chemistry related to our daily lives?
What is an element?
What is a compound?
Are the properties of a compound related to the
elements forming it?
6. What is a mixture?
7. What are the differences between a compound and
a mixture?
8. How can matter be classified?
9. What are physical properties?
10. What are chemical properties?
11. What is a physical change?
12. What is a chemical change?
13. What are the main potential dangers when working
in a chemistry laboratory?
14. What are the common apparatus used in a
chemistry laboratory?
END
Chapter 1 What is Chemistry?