1.1 WHAT IS CHEMISTRY ABOUT? WHAT IS WHAT IS CHEMISTRY CHEMISTRY ABOUT? ABOUT?
Jan 12, 2016
1.1 WHAT IS CHEMISTRY ABOUT?
WHAT ISWHAT IS CHEMISTRYCHEMISTRY
ABOUT?ABOUT?
StructuresStructures
CHEMISTRYCHEMISTRYCHEMISTRYCHEMISTRY
ChangesChangesPropertiesPropertiesCompositionsCompositions
Substances
• MatterMatter- It is anything that occupies - It is anything that occupies spaces spaces and has and has mass.mass.
• Substances Substances - - A particular type of matter. A particular type of matter. (a simple form of matter)(a simple form of matter)
IRONIRON
A LITTLE HISTORY OF CHEMISTRY
Fire can change one thing to anotherFire can change one thing to another
AlchemistsAlchemists
Cheap Metals -----> GoldCheap Metals -----> Gold
Figure 1.2
"The alchemist", by S
ir William Fettes Dou
glas, 1853
The Philosopher's Stone (fairy tale) The Philosopher's Stone (fairy tale) According to the alchemists, According to the alchemists, the key to changing lead into gold was the the key to changing lead into gold was the Philosopher’s StonePhilosopher’s Stone. This wasn’t actually a stone but powder, of which . This wasn’t actually a stone but powder, of which only a small quantity was required. It was believed the Philosopher’s only a small quantity was required. It was believed the Philosopher’s Stone was to be made from mercury purified through hundreds of different Stone was to be made from mercury purified through hundreds of different processes. processes.
If you can come up with a If you can come up with a way to change lead into way to change lead into gold, you would soon gold, you would soon become a millionaire. become a millionaire. However, However, none none of the of the alchemists became rich man.alchemists became rich man.
Robert Boyle (1627-1691), ‘The Father of Chemistry’ Robert Boyle (1627-1691), ‘The Father of Chemistry’
• Denied the Greek classical elementsDenied the Greek classical elements (earth, fire, air, and water ) (earth, fire, air, and water )
• Hypothesized that matter consisted of atoms Hypothesized that matter consisted of atoms
1.2 CHEMISTRY IN OUR LIVES TODAY
燒肉驗出致癌物二氯丙醇 燒肉驗出致癌物二氯丙醇
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」「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,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 對於寬鬆,指世及 對毒性強烈的二氯丙醇是「零容忍」毒性強烈的二氯丙醇是「零容忍」,絕不容食物含該有毒物,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。 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。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。 、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。
07月 18日
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, semi-conductors
1.6 OBSERVATION, INTERPRETATION AND PREDICTION IN CHEMISTRY
OBSERVATION in chemistry includes four activities:
1.5 Observation, interpretation and prediction in chemistry
Seeing with eyes
Feeling with hands
Smelling with nose
Hearing with ears
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
2. Report clearly
and accurately
3. Analyse and
interpret the results
4. Draw conclusions
and make predictions
Laboratory safetyLaboratory safetyLaboratory safety is of first importance in any experimental work.
BASIC LABORATORY SAFETY RULES
(2) Follow strictly the instructions given by your teacher.
(1) Do not work in the laboratory unless your teacher is present.
(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.
(6) Report all accidents and breakages to your teacher at once.
(5) Clean up all the spillage (on the floor or bench) at once. Clean up the bench after experiment.
(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.
x
A 1.7
1.7 HAZARDOUS CHEMICALS1.7 HAZARDOUS CHEMICALS
CLASSIFICATION OF HAZARDOUS CHEMICALS
explosive oxidizing flammable
1.7 Hazardous chemicals
carcinogenic toxic harmful
corrosive irritant
1.7 Hazardous chemicals
i
(a)(a)
(b)(b)
(c)(c)
(e)(e)
(d)(d)
Flat-bottomed flask
Round-bottomed flask
Clamp
Retort stand
Conical flask
1.8 Common chemical apparatus
(f)(f)
(g)(g)
(h)(h)(i)(i)
(j)(j)
(m)(m)
(k)(k)
(n)(n)
(l)(l)Wire gauze
Evaporating basin
TripodCrucible
Pipeclay triangle
Bunsen burner
Crucible
tongs
Spatula
Heat-resistant mat
1.8 Common chemical apparatus
(q)(q)
(p)(p)
(o)(o)
Mortar
Desiccator
Pestle
1.8 Common chemical apparatus
(r)(r)
(s)(s)
(t)(t)(u)(u)
(v)(v)
(w)(w)
Test tube holder
Test tube rack
Test tubeBoiling tube
Dropping bottle
Reagent bottle
1.8 Common chemical apparatus
(y)(y)
(dd)(dd)
(z)(z)
(aa)(aa)
(bb)(bb)
(ee)(ee) (ff)(ff)(cc)(cc)(x)(x)
(gg)(gg)
Gas syringe
Measuring
cylinder
Beaker
Funnel
Plastic washbottle
Teat pipette
Thermometer
Watch glass
Separating
funnel
Glass rod
1.8 Common chemical apparatus
SaltSalt
SugarSugar
PlasticPlastic PaperPaper
CHEMISTRY CHEMICALS (MATTERS)
How to classify matter?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 WHAT IS AN AN ELEMENTELEMENT??
An ELEMENT is a pure substance that canno
t be broken down into anything simpler by ch
emical methods.
e.g Iron, Carbon, Oxygen
Are they elements?
• Water
• Carbon dioxide
• Sand (silicon dioxide)
PERCENTAGE BY MASS OF ELEMENTS IN NATURE
all other elements 2.8%
iron 4.1%
8.1% calcium 3.2%sodium 2.3%
potassium 2.3%magnesium 2.1%
46.6%
27.7%
Figure 2.16 Percentage
abundance by mass of
elements in nature.
______________
______________oxygen
____________________aluminium
silicon
2.2 Elements in nature
OxygenOxygenOxygenOxygen50% by 50% by mass of mass of
all elementsall elements
50% by 50% by mass of mass of
all elementsall elementsFree Free
elementelement & & compoundscompounds
Free Free elementelement & & compoundscompounds
Most Most abundant abundant element in element in
naturenature
Most Most abundant abundant element in element in
naturenature
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 AWHAT IS A COMPOUNDCOMPOUND??
Are they elements?
• Water • Carbon dioxide• Sand (silicon dioxide)
• No. They are compounds.
• hydrogen + oxygen• Carbon + oxygen• Silicon +oxygen
Elements chemically combined together
Pure substances
Made up of two or more
elements
COMPOUNDS
SaltSalt
SugarSugar
PlasticPlastic PaperPaper
HydrogenHydrogenHydrogenHydrogen
OxygenOxygenOxygenOxygen
For For exampleexample
+WATERWATERWATERWATER
electrolysis
Sodium Chloride
heating
reads 'reacts with' reads 'to produce'
copper + chlorine copper(II) chloride
reactants products
(reacting substances) (substance produced)
2.3 Compounds
Figure 2.20 Combining copper and chlorine to form a new substance — the
compound copper(II) chloride.
(a) Heating of copper powder to red hot in a deflagrating spoon.(b) Reaction of hot copper with chlorine to form brown copper(II) chloride solid.
deflagrating spoon
chlorinecopper powder
brown copper( chloride
(a) (b)
brown copper(II) chloride
How to classify matter?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 i
nto anything simpler by chemical methods.
e.g Iron, Carbon, Oxygen
An Compound is a pure substance made up of 2 or more elem
ents 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!!
Sodium Chloride
heating
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 ?
OxygenOxygenOxygenOxygen
Which is the most abundant metal ?
AluminiumAluminiumAluminiumAluminium
DECOMPOSITION OF COMPOUNDS
A-B-CA-B-C
ElementElementCC
ElementElementCC
decomposed byheat or electricity (electrolysis)
ElementElementBB
ElementElementBB
ElementElementAA
ElementElementAA
DECOMPOSITION OF WATER
HH22OO
HHHH
decomposed byheat or electricity (electrolysis)
OOOO
HHHH
Figure 2.21 Decomposition of mercury(II) oxide into mercury and oxygen by the
application of heat.
mercury(II)oxide Bunsen
flame
mercury vapour
glowingsplint
glowing splint
relighted by oxygen
(a) (b) (c)
How to classify matter?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 WHAT IS A MIXTUREMIXTURE??
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:
2.4 Compounds and mixtures
ElementElementElementElement CompoundCompoundCompoundCompound
ElementElementElementElement ElementElementElementElement
CompoundCompoundCompoundCompound CompoundCompoundCompoundCompound
DIFFERENCES BETWEEN MIXTURES AND
COMPOUNDS (EXPT 1.1)
We can study the differences between a mixture and a compoun
d by comparing a mixture and the compound of iron and sulphur.
Element Element Compound
Sulphur Iron Iron(II) sulphide
Compare Colour and Physical State
Observation
Sulphur 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.
Structure
Gives toxic hydrogen sulphide gas (with smell of bad eggs)
Only iron reacts to liberate hydrogen gas
No reactionLiberates hydrogen gas
Action of dilute hydrochloric acid
SinksAll iron and most sulphur sink, while a little sulphur floats
Most sulphur sinks, while a little floats
SinksAction of water
not attracted by magnet
Only iron attracted by magnet
Not attracted by magnet
Attracted by magnet
Action of magnet
Black solidYellowish grey solidYellow solidBlack solidAppearance
Iron(II) sulphideIron/sulphur mixtureSulphurIronProperty or test
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
Constituent elements can only be separated by chemical methods, not by physical methods
Constituents can be separated by physical methods, based on differences in physical properties
5. Separation of
constituents
Properties are entirely different from those of constituent elements
Each constituent substance retains its own properties
4. General properties
Melts or boils at a definite temperature (i.e. with a sharp m.p. or b.p.)
Melts or boils over a wide range of temperatures (i.e. does not have a sharp m.p. or b.p.)
3. Melting point (m.p)
and boiling point
(b.p.)
A chemical reaction takes place; heat is usually given out or absorbed when a compound is made
No chemical reaction takes place; usually no heat change in making a mixture
2. Changes in formation
Fixed (e.g. in water, the ratio by mass of hydrogen to oxygen is always 1:8)
Variable (the substances in the mixture can be mixed together in any proportion)
1. Composition by mass
CompoundMixture
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.
Gold has a higher density.Gold has a higher density.
Gold is softer.Gold is softer.
Copper will slowly tarnish in air.Copper will slowly tarnish in air.
How can we differentiate these 2 coins? Which How can we differentiate these 2 coins? Which is made of gold? Which is made of copper?is made of gold? Which is made of copper?
1.4 PROPERTIES OF SUBSTANCES
PHYSICAL PROPERTIES
Appearance
Odour
Hardness
Taste
Malleabilit
y
Ductility
Electrical
conductivit
y
Thermal conductivit
y
Solubility
Density
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. 1.22Cutting 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 water water vapourmelting boiling
condensationfreezing
Change of state is a common example of physical change.
heat absorbedheat given out
sublimation
boilin
g
cond
ensa
tionfreezing
melting
solid gas
liquid
deposition
1.9 Physical and chemical changes
Figure 1.26 Iodine solid sublime
s to form vapour on heating. Wh
en in contact with a cool surface,
the iodine vapour changes back
directly to iodine solid, without p
assing through the liquid state.
evaporating basin
iodine
solid
iodine
vapour iodine solid
water
Bunsen flame
(cool surface)
Chemical changeChemical changeA chemical change is a change in which one or more new substances are formed.
Fig. 1.25Burning a piece of paper is a chemical change.
Class practice 1.5Class practice 1.5
CHEMICAL CHANGE
1.9 Physical and chemical changes
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 pieces2. Breaking a glass3. Boiling water into steam4. Melting ice into water5. Burning A piece of paper
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.
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
1.9 Physical and chemical changes
(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. What is chemistry about?
2. In what ways is chemistry related to our daily lives?
3. What is an element?
4. What is a compound?
5. 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?
ENDENDENDEND
Chapter 1 What is Chemistry?