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?