Chapter 4Matter and Substances

4.1 Changes In Matter Kinetic Theory of MatterThe theory states that:- Matter is made up of tiny and discrete

particles- The particles are always moving in

random motion- The moving energy is called the

kinetic energy of particles- The kinetic energy of particles

depends on the temperature of matter

States of Matter

Changes in state of matter

Sublimation

Sublimation

4.2 Structure of atom1. Every substances is made up of

atoms.2. There are three types of subatomic

particles: proton, electron and neutron.

(e, negatively charged)

(p, positively charged)

(n, neutral/ no charged)

4.3 Proton number and Nucleon numberProton number is the number of proton

in an atom.Nucleon number is the total number of

protons and neutrons in an atom.

The number of nucleon = neutrons number + proton number

• Symbol of element. For example, Aluminium (Al)

13

27Al Name of element

Proton number(always smaller number)

Nucleon number

How to determine the charges of particles

Particles Number of protons

Number of electrons

A 6 8

B 10 9

C 11 11

a)Positively charged particles: B ( more proton number)b)Negatively charged particles: A (more electron number)c) Particle that has no charge (neutral): C (proton = electron)

Isotopes Isotopes of certain elements contains

the same number of protons but a different number of neutrons in their atoms.

For example, hydrogen

4.4 Periodic table

•Elements are arranged according to their proton number (increases)•Divided into metals, non-metals and semimetals•Elements in the same group have same chemical properties

Importance of periodic tableHelps us to determine the

properties of elements.Can be used to forecast the

properties and uses of particular element.

4.5 Properties of Substances

ATOMS

•Substances made up of atoms only.•The smallest particle.

MOLECULES

Substance made up of molecules only (two or more atoms).

IONS

•Substance made up of ions only.•Contain charged particle

•In solid (except mercury)•Conduct electricity•High boiling/melting point

•In solid, liquid or gas•Cannot conduct electricity•Low boiling/melting point

•In solid•Cannot conduct electricity except in molten or aqueous states•High boiling/melting point

Oxygen gas

Water Sodium chloride (NaCl)Aluminiu

mAtom

ALUMINIUM

Physical properties of substance made up of atoms, molecules and ions

Lead/sulphur/Lead(II)bromide

Substances

Type of substance

Melting point

Lead ATOM High

Sulphur MOLECULE Low

Lead (II) Bromide

ION High

•High melting point = strong forces of attraction

•Low melting point = weak forces of attraction

Section A: Melting point.

Section B: Electrical conductivity

SUBSTANCE ELECTRICAL CONDUCTIVITY

SOLID MOLTEN

LEAD Can Can

SULPHUR Cannot Cannot

LEAD(II)BROMIDE

Cannot Can

For ionic substance, lead(II)bromide:•Does not conduct electricity in solid because

- ions cannot move freely •Conducts electricity in molten because

- ions can move freely

4.6 Properties of Metals and Non-Metals

A) Surface condition

Metals: copper

Non-metals: carbonShiny surface

Dull

B) Malleability

•Non-metal: Brittle• the lump of carbon shatters

•Metal :Malleable• iron wire changes shape

C) Tensile strength

Nichrome/nylon

Nichrome (metal) needed more weights to break

Nylon (non-metal) needed less weight to break

Metals have higher tensile strength than non-metals

D) Electrical conductivity

* Metals: the bulb lights up with copper rod* METALS conduct electricity

* Non-metals: the bulb does not lights up with glass rod* NON-METALS do not conduct electricity

E) Heat conductivity

Type of materials

Example

Time taken for the thumbtack to drop off/seconds

METALS Copper rod

96

NON-METALS

Glass rod

130

•Metals: copper rod are good heat conductors•Non-metals: glass rod are poor heat conductors

4.6 Properties of Metals and Non-Metals

Comparison between metals and non-metalsMETALS Physical properties NON-METALS

Shiny Surface Dull

Ductile Ductility Non-ductile/ brittle

Malleable Malleability Non-malleable

High Melting and Boiling point

Low

Good Electrical conductivity

Non-conductive except carbon

Good Heat conductivity Poor

High Tensile strenght Low

Uses of metalsIron is used in making

cars

Silver is often used to make

jewellery

Aluminium is used to make power lines

Copper is used to make

wires

Uses of non-metals

Diamonds are mostly

used to make

jewellery

Sulphur is ingredient in making paint

Sulphur is used to make

matchstick tips

4.7 Purification of Substances

1. Pure substances are substances that contain only one type of substance.- do not have any impurities- for example,

* pure sugar only contains sugar molecules

* pure water only contains water molecules

2. Pure substances have fixed boiling and melting point.- for example,

* pure water boils at 100°C

Effect of impurities on the boiling point of a pure liquid

The presence of impurities in a pure substance cana) increase its boiling pointb) decrease its freezing point

• For example,- when a salt is added to pure water, water will be boil at a temperature higher than 100°C

Title: Effect of impurities on the boiling point of a pure liquid (PEKA)

Aim: To study the effect of impurities on the boiling point.

Hypothesis: The presence of salt increases the boiling point of a pure liquid

Variables:manipulated variable :responding variable :constant variable :

Materials: distilled water, table saltApparatus: 100cm³beaker, wire gauze, tripod

stand, Bunsen burner, thermomater

Procedure: 1. Distilled water was filled into a beaker until it is half full.

2. The water was heated until its boils. The temperature was recorded.

3. Two spatulas of table salt were added into the distilled water and the mixture was heated again.

4. The boiling point of the mixture of water and table salt were recorded.

Salt

Distilled water

Results : The presence of table salt

Boiling point of distilled water (°C)

Absent 100

Present

• Analysis:

• Conclusion:

Methods of purificationPurification is a process of removing impurities

from a substance.The methods are:a) Filtration: process of separating solid from

liquid

Mixture of solid and liquid

Filter paper

Residue (solid)

Filtrate (liquid)

b) Crystallisation : process of forming crystals from a liquid or gas- production of salt from sea water- production of pure solid copper(II)sulphate from its solution

Substance in crystal form

c) Distillation: a process to obtain a pure liquid from a solution of liquid mixture. - production of distilled water- petroleum fractions (fractional distillation)

Porcelin chips:To break up the air bubbles

Tap water flows to cool the vapour and condense it into liquid

To make sure the condenser is fully filled with water

Fractional distillation

4.8 Uses of various substances

Humans need various types of substances in daily life.

With scientific knowledge and technology, humans have used the properties of substances to make their lives better.

For example, pure metals which may not be suitable for a particular purpose because they are too heavy or rust easily.- they can be processed into more suitable substances.- pure iron steel (strong and does not rust)

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