(kimia)1a chapter1 introduction 23

8/8/2019 (KIMIA)1A Chapter1 Introduction 23

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INTRODUCTION TOCHEMISTRY

Umi Kulsum and Sri Sugiarti

SMA Negeri I Probolinggo

Supervised by

EffendyJurusan Kimia, FMIPA

Universitas Negeri Malang (UM)


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There are some phenomena that you

see in everyday life such as:

Corrosion of nail

Combustion of gasoline in the carto give energy

Photosynthesis

All of them are related to chemistry


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What is chemistry?

Chemistry is a branch of science

which deals with the properties of

matter, structure of matter, changesin matter, the laws and principles

describing these changes, and the

concepts and theories that interpret

them.


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Why should you study chemistry?If you want to be a geologist, youhave to understand chemistry to

study constituents and structure ofminerals.

If you want to be a doctor, you haveto understand chemistry to select aparticular anesthetic for surgery.


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If you want to be a civil engineer you

have to understand chemistry toselect the best cement to build the

road.

You have to study chemistry

because chemistry is an important

part to prepare your particular

future career.


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The basic object of chemistry is

elements.

What is an element?

An element is a fundamental

substance that cant be chemically

changed or broken down intoanything simpler.


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How many presently known

elements?

115 elements

90 natural elements

25 artificially elements produced

using high energy accelerators


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How do chemists represent an element?

By using one-, two-, or three-lettersymbols of an element

Examples:H for hydrogen

N for nitrogen

Al for aluminum

Mg for magnesium

Uun for ununnilium


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aluminum magnesium


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The periodic table consists of

horizontal rows called periods and

1 vertical columns called groups

The international standard calls for

numbering the columns or groups from 1to 1 going from left to right.

The US system uses reek number andcapital letters

The elements are tabulated based ontheir chemical properties


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There are actually 2 groups in the

periodic table rather than 1 , but to

make the table fit manageably on a

page, the 1 elements following

lanthanum (the lanthanides) and the

1 elements following actinium (the

actinides) are pulled out and shownbelow the others. These groups are not

numbered.


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Groups 1, 2, 1 , 1 , 15, 1 , 1 and 1 are called

main or representative groups.Groups to 12 are called transition metal

groups.

The others are called lanthanides and actinides

groups.

The elements in the lanthanides group followlanthanum.

The elements in the actinides group followactinium. The elements in the lanthanides and

actinides groups are called inner transitionelements.


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1

2

3

4

6

7

1)

(2)

(3) (4) (5) (6) (7) (8) (9) (10) (11) (12)

(13) (14) (15) (16) (17)

(18)

roup

IA

IIA

IIIB VBIVB VIB

VIIIB

VIIB IB IIB

VIIIA

IVAIIIA VA VIIAVIAH

Na

L Be

Ca

Mg

Sr

Ra

Ba

Fr

Sc

Y

Ac

La

Ti

Zr

Rf

Hf

V

Nb

Db

Ta

Cr

Mo

Sg

Mn

Tc

Bh

Re

Fe

Ru

Hs

Os

Co

Rh

Mt

Ir

Ni

Pd

Uun

Pt

Cu

Ag

Uuu

Au

Zn

Cd

Uub

Hg

B

Al

In

a

Tl

C

Si

Sn

e

Uuq

Pb

N

P

Sb

As

Bi

O

S

Te

Se

Uuh

Po

F

Cl

I

Br

At

Ne

Ar

Xe

Ke

Uuo

Rn

He

Ce Pr Nd Pm Sm Eu d Tb Dy Ho Er Tm Yb Lu

Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

Lanthanides

Actinides

Main groupMain group

Transition metals group

Post transition metal


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1

2

3

4

5

6

7

Period

1

2

3 4 5 6 7 8 9 10 11 12

13 14 15 16 17

18

Alkali metals group

Alkaline earth metals group

Halogen group

Noble gases group

i

Na

K

Rb

Cs

Fr

Be

Mg

Ca

Sr

Ba

Ra

He

Ne

Ar

Kr

e

Rn

F

Cl

Br

I

Cu

Ag

Au

Coinage metals group

Group

Some groups may have specific name


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The elements in the periodic table

are often divided into three mayor

classes:

Nonmetal,

Metal

Semimetal or metalloid


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Most of the elements known are naturally

occurring elements.

Some of the elements are synthetically

prepared.

At 0 C the elements might be solid,

li uid or gas.


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1

2

34

5

6

7

Period

(1)

(2)

(3) (4) (5) (6) (7) (8) (9) (10) (11) (12)

(13) (14) (15) (16) (17)

(18)

Group

IA

IIA

IIIB VBIVB VIB

VIIIB

VIIB IB IIB

VIIIA

IVAIIIA VA VIIAVIAH

Na

Li

K

Cs

Rb

Be

CaMg

Sr

Ra

Ba

Fr

Sc

Y

Ac

La

Ti

Zr

Rf

Hf

V

Nb

Db

Ta

Cr

Mo

Sg

W

Mn

Tc

Bh

Re

Fe

Ru

Hs

Os

Co

Rh

Mt

Ir

Ni

Pd

Uun

Pt

Cu

Ag

Uuu

Au

Zn

Cd

Uub

Hg

B

Al

In

Ga

Tl

C

Si

Sn

Ge

Uuq

Pb

N

P

Sb

As

Bi

O

S

Te

Se

Uuh

Po

F

Cl

I

Br

At

Ne

Ar

Xe

Ke

Uuo

Rn

He

Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

Lanthanides

Actinides

Gas SolidLiquid Synthetically prepared


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The kinetic energy differences

betweengas, liquid, and solid

gas liquid solid


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Where did the elements come from?

All the elements in the universe except

hydrogen and most of the helium were

made in the stars.

Seconds after the universe came into

being with the BigBang, the only element

present were the two simplest, hydrogen

and helium.


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After millions of year, as the universe

cooled, the atoms of hydrogen and

helium collected together in large

clouds under the influence of gravity.

These clouds gradually became hotter

and hotter as they contracted, and indue course they burst into

incandescence as stars.


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Within the stars, intense heat causes

atoms of hydrogen to smash together,merge, and became atoms of other

elements.

Many million years after a star is

formed and it begins to cool, its outer

layers may collapse, like a fallingroof, into its exhausted core.


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This mighty star uake produces such

great shock waves that the star shrugs offits outer layers and sends them into space

in a huge explosion called supernova.

The shock of explosion raises the

temperature in the star, making it even

brighter than before. At such high

temperatures, the heavy atoms collide

violently enough to merge and become

heavier ones.


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Most of substances in the world are

compounds.

What is compound?

Compound is a pure substance that isformed when atoms of two or more

different elements combine and create a

new material with properties completelyunlike those of its constituent elements.


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Formation of a compound

from its elements involves a

chemical change, called

chemical reaction


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Hydrogen (colorless gas)

combines with oxygen (colorless

gas) to give water (colorless

li uid).

2H2(g) + 2(g) 2H2 (l)


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In the compound, the elements no

longer have the same propertiesthey had before they were

combined.

The properties of H2O is different

from the properties of H2 and O2.


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A compound is written by giving its chemical formula,

which lists the symbols of the individual constituent

elements and indicates the number of atoms of eachelement with subscript

Chemical

formula

of compound

Constituent elements

H2O

HCl

H2SO

NH

Two hydrogen and one oxygen atoms

One hydrogen and one chlorine

atomsTwo hydrogen, one sulfur, and four

oxygen atoms

One nitrogen and three hydrogen

atoms


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Classification of matter

Matter

re s stance i t re

lements Com o n s

omogeneo seterogeneo s

(fixed compositionand properties)

(can bedecomposedby chemical

reaction)

(can not bedecomposed)

(nonuniformcomposition)

(uniformcomposition)

C emicallyse ara le into

Com inec emically to

form

ysicallyse ara le into


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Heterogeneous mixture:

A mixture with a composition that variesfrom point to point

Examples:mayonnaise

chocolate chip cookies

concrete


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Homogeneous mixture:

A mixture with a composition that doesntvary from point to point

Homogeneous mixture is also called

solution

Examples:

Mixture of water and alcohol

Mixture of table salt and water

Mixture of sugar and water


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Separation of mixtures

Mixture of iron and sulfur may be

separated by using a magnet


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Mixture of two li uids with different boiling points such asmixture of water and alcohol may be separated by distillation


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Mixture of colored substances such as the components of agreen ink may be separated by column chromatography


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Mixture of two crystalline substances

such as barium chromate, BaCrO ,and strontium chromate, SrCrO ,

may be separated by fractional

crystallization.

Barium chromate is less soluble in

water than strontium chromate.Barium chromate crystallizes before

strontium chromate.


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Compounds can not be separated by

physical means; they can be separated bychemical means which involve chemical

reactions.

2 2(g) 2(g)2 2 (l)Electrolysis


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Reaction of mercury (A) and oxygen gas givesmercury(II) oxide (B). Heating of mercury(II)

oxide gives metallic mercury and oxygen gas (C)


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Properties of Substances

Any characteristic that can be used to

describe or identify matter is called a

property.

Properties of substances can be

classified as either intensive or

extensive.


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Intensive properties:

does not depend on the amount of

sample

Examples:Temperature

Melting point

Density

Taste


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Extensive properties:

depends on the amount of

sample

Examples:

Mass

olume


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Properties can also be classified as

either physical or chemical,depending on whether the property

involves a change in the chemical

makeup of substance

Physical properties:

Characteristics that do not involve achange in a samples chemical

makeup


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Example of physical properties:

Melting point and boiling point of

substance

Melting point of ice and boiling point ofwater are physical properties because

melting and boiling cause the water to

change only in form or phase, but do notin chemical makeup


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Chemical properties:

Characteristics that do involve a change in asamples chemical makeup

Example:

Rusting of iron

Rusting of iron is a chemical property,

because iron combines with oxygen and

moisture from the air to give the newsubstance


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Some Examples of Physical

and Chemical Properties

Physical Properties Chemical properties

Temperature

ColorMelting point

Electrical conductance

Amount

Odor

Solubility

Hardness

Rusting (of iron)

Combustion (ofgasoline)

Tarnishing (of silver)

Hardening (of

cement)

Decomposition (of

sugar)


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Summary

1. Chemistry is a branch of science which deals withthe properties of matter, structure of matter,changes in matter, the laws and principlesdescribing these changes, and the concepts andtheories that interpret them.

2. The basic object of chemistry is elements. Only 90of 115 presently known elements occur naturally.The remaining ones have been produced artificiallyusing high energy accelerators.

. The elements are tabulated in a table calledperiodic table which consists of horizontal rows,called periods, and 1 vertical columns, calledgroups.


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4. The elements in the periodic table are often

divided into three mayor classes: metal,

nonmetal, and semimetal or metalloid.

5. Compound is a pure substance that is

formed when atoms of two or more

different elements combine.

. A compound is written by giving its

chemical formula, which lists the symbols

of the individual constituent elements andindicates the number of atoms of each

element with subscript.


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7. Matter can be classified either pure

substances or mixtures. It can be elements

or compound.

. A mixture is composed of two or more

substances that can be present in varying

amounts. Formation of mixtures onlyinvolves a physical change.

9. A mixture with a composition that doesnt

vary from point to point is called ahomogeneous mixture (solution).


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10. Mixture can be separated using distillation,fractional crystallization, chromatography

etc.

11. Formation of a compound from its elementsinvolves a chemical change, called chemical

reaction.12. Compounds can be separated by chemical

means which involve chemical reactions.

1 . Any characteristic that can be used todescribe or identify matter is called aproperty. Properties can be classified aseither intensive or extensive.


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(kimia)1a chapter1 introduction 23

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