O level Chemistry

1. PURE CHEMISTRY
‘O’ LEVEL
LESSON 2
21/11/2019

2. Lesson Plan For Today
1. Diagnosis question (15 mins)
2. Answering Technique (15 mins)
3. Topic 2: The Particulate Nature of Matter (25 mins)
4. Topical Revision (20 min)

3. 1. Answering Technique -Grammar
• Short answer question answering technique
-remove unnecessary words, convoluted sentence structure
-make brief statements
-use active versus passive sentence structures
-use keywords
-avoid writing beyond the lines given
Q4(b)(II) explain why brass is harder than either of the pure metals (2 mark)
1- Pure metals contains atoms that are arranged in a regular lattice. The atoms are able to
Slide over one another. In brass, presence of foreign atoms disrupts the regular arrangement.
This prevents the atoms from sliding.
2- Pure metals contains atoms that are arranged in a regular lattice and so the atoms are able to
Slide over one another. But in brass there are more than one atoms with different sizes.
The atoms cannot be regularly arranged and so prevents the layers from slipping. This explains
why brass is harder than pure metals.

4. 2. Answering Technique - Linking Topics
Identity correlation between topics
acid, bases and salts is strongly interlinked with periodic table, metals and chemical
bonding
Study them together as 1 theme
eg. Reaction of metals with acid, types of oxides formed by metals vs non metals, dot
and cross diagram for ionic bonding

5. 3. Answering Technique- The 3 Con Method
Answering the context of the question
-consider and mention the parameters and given information from the question (which could
include numeraical values, graph, tables, diagrams-etc)
Deploy the appropriate concept (background knowledge/ theory)
-explain the contextual cues given in the questions. Use your background knowledge/textbook
information to analyse the question
Directly answer to conclude question
-answer based on focus of questions. Look at directive words (explain, discuss, what…etc)

6. Homework
QNS (A2)(a)(i) complete the equation for reaction 1 by filling in the missing state
symbols
AgNO3( aq ) + KX( aq ) AgX( s ) + KNO3( aq)
QNS (A2)(a)(ii) one of the reaction is a redox reaction , the other is not. Use the
oxidation state to show that this reaction is true
Reaction 2 is a redox reaction. Reaction 1 is not. In reaction 2, the oxidation state of
silver is reduced from +1 in silver ion to 0 in silver metal. Thus reduction occur. For
halide, its oxidation state is increased from -1 in halide ions to 0 in a halogen.Thus
Oxidation occurs. In reaction1, the oxidation state of all the elements remain the
same, thus it is not a redox reaction.
(technique used: 1and 3)

7. Homework
QNS (A2)(b)(i) complete the table to show the color of the silver iodide
Yellow
QNS (A2)(b)(ii) what conclusion can you make from the table about the relationship between
the reactivity of the halogen and the rate of breakdown of the silver halides
The reactivity of halogen decreases down the group. The rate of breakdown decreases with the
decreased in reactivity of halogen down the group
technique: 2 and 3

8. Homework
QNS (A5)(a)what is the order of reactivity of the four metals?
Most reactive: magnesium, chromium, cobalt, copper
QNS (A5)(b)magnesium sulfate is colourless. Complete the table below to
show the colours of the other metal sulfate solutions
Metal sulfate Colour of the solution
copper(II) sulfate blue
cobalt(II) sulfate pink
chromium (III)
sulfate
green

9. Homework
QNS (A5)(c)(i) complete the energy profile diagram betwen chromium and cobalt(II)sulfate solution
-Your diagram should include the products of the reaction
-lables to show the enthalphy change of the reaction and the activation energy
QNS (A5)(c)(ii)write an ionic equation to show the reaction when chromium metal is added to a solution of cobalt(ii) solution
2Cr(s) + 3Co2+(aq) —> 2Cr3+aq) + 3Co(s)
QNS (A5)(d)the student added calcium to separate samples of each of the four salt solutions. The students observed fizzing.
Explain this observation.
Calcium is a very reactive metal. It will react with water to form Ca(OH)2 and H2 gas causing ‘fizzing’.
Activation energy
Cobalt
and chromium (III)
sulfate
Chromium and
cobalt (II) sulfate

10. Homework
OR (B9)(a) give the empirical formula of poly(propene)and molecular formula of propanol
Polypropene CH2, propanol C3H8O
QNS (B9)(b) compare the bonding and structures of the 3 compounds
All 3 compounds contain covalent bonds between atoms in their structure. Silicon dioxide exhibit
atoms bonded by covalent bonds to form giant covalent structure while propanol shows atoms bonded
to form simple covalent structure. In polypropene, the atoms are bonded by covalent bonds to form
long chains of polymeric structure. There are weak intermolecular forces of attraction between the small
propanol molecules as well as between the long chains of hydrocarbon molecule of poly(propene)
QNS (B9)(c) explain why the melting points of the 3 compounds differ from each other
A large amount of energy is needed to break strong covalent bonds between the silicon and oxygen
atoms in silicon dioxide and thus it has a very high melting point. A small amount of energy is needed
to overcome the weak intermolecular forces of attraction between the small propanol molecules and
thus it has low melting point. The intermolecular forces of attraction between the polypropene
molecules are weak but stronger than those in propanol because of the larger molecular size in
polypropene.

11. 2. THE PARTICULATE NATURE OF MATTER

12. Syllabus
2 The Particulate Nature of Matter Content
• 2.1 Kinetic particle theory
• 2.2 Atomic structure
• 2.3 Structure and properties of materials
• 2.4 Ionic bonding
• 2.5 Covalent bonding
• 2.6 Metallic bonding
Learning Outcomes
Candidates should be able to:
2.1 Kinetic particle theory
• (a) describe the solid, liquid and gaseous states of matter and explain their interconversion in terms of the kinetic particle theory and of the
energy changes involved
• (b) describe and explain evidence for the movement of particles in liquids and gases (the treatment of Brownian motion is not required)
• (c) explain everyday effects of diffusion in terms of particles, e.g. the spread of perfumes and cooking aromas; tea and coffee grains in water
• (d) state qualitatively the effect of molecular mass on the rate of diffusion and explain the dependence of rate of diffusion on temperature.

13. • 2.2 Atomic structure
• (a) state the relative charges and approximate relative masses of a proton, a neutron and an electron
• (b) describe, with the aid of diagrams, the structure of an atom as containing protons and neutrons (nucleons) in the nucleus and
electrons arranged in shells (energy levels)
(knowledge of s, p, d and f classification is not required; a copy of the Periodic Table will be available in Papers 1 and 2)
• (c) define proton (atomic) number and nucleon (mass) number
• (d) interpret and use symbols such as 12 C
• (e) define the term isotopes
• (f) deduce the numbers of protons, neutrons and electrons in atoms and ions given proton and
nucleon numbers.
• 2.3 Structure and properties of materials
• (a) describe the differences between elements, compounds and mixtures
• (b) compare the structure of simple molecular substances, e.g. methane; iodine, with those of giant molecular substances, e.g.
poly(ethene); sand (silicon dioxide); diamond; graphite in order to deduce their properties
• (c) compare the bonding and structures of diamond and graphite in order to deduce their properties such as electrical conductivity,
lubricating or cutting action (candidates will not be required to draw the structures)
• (d) deduce the physical and chemical properties of substances from their structures and bonding and vice versa.

14. • 2.4 Ionic bonding
• (a) describe the formation of ions by electron loss/gain in order to obtain the electronic configuration of a noble gas
• (b) describe the formation of ionic bonds between metals and non-metals, e.g. NaCl; MgCl2
• (c) state that ionic materials contain a giant lattice in which the ions are held by electrostatic attraction,
e.g. NaCl (candidates will not be required to draw diagrams of ionic lattices)
• (d) deduce the formulae of other ionic compounds from diagrams of their lattice structures, limited to
binary compounds
• (e) relate the physical properties (including electrical property) of ionic compounds to their lattice structure.
• 2.5 Covalent bonding
• (a) describe the formation of a covalent bond by the sharing of a pair of electrons in order to gain the electronic configuration of a
noble gas
• (b) describe, using ‘dot-and-cross’ diagrams, the formation of covalent bonds between non-metallic elements, e.g. H2; O2; H2O; CH4;
CO2
• (c) deduce the arrangement of electrons in other covalent molecules
• (d) relate the physical properties (including electrical property) of covalent substances to their structure and bonding.

15. All matter are made of particles that are in constant random motion
This account for the properties of the 3 states of matter i.e. solid, liquid, gas and changes of states
Solid Liquid Gas
Structure
Packing of particles
Tightly packed.
Arranged in an orderly
manner
Packed closely together. No
regular arrangement
Spaced apart from each
other
Forces of attraction
between particles
Very strong forces of
attraction
strong forces of attraction Weak forces of attraction
Movement of
particles
Can only vibrate and
rotate about fixed
position
Particles can vibrate, rotate
and slide part one another
Particles move freely at
high speed
Shape Fixed shape
Not fixed. Takes on the
shape of the container it is in
Not fixed. Takes on the
shape of the container it
Volume
Fixed volume. Not easily
compressed
Fixed volume. Not easily
compressed
No Fixed volume. Easily
compressed
2.1 KINETIC PARTICLE THEORY

16. •The Kinetic Particle Theory explains the changes that occur when matter changes state.
•Generally, heating causes particles to gain kinetic energy and move about more rapidly.
•The movement can be rotational, vibrational or even translational in nature.
•Sufficient energy overcomes forces of attraction and ultimately causes a change of state.
•Conversely, cooling or reducing the amount of kinetic energy of particles has the reverse effect.
•I.e. particles loses energy and move about slowly
Interconversion of State of Matter
Matters can be converted between the solid, liquid and gaseous states.

17. Interconversion of State of Matter -Boiling Curve
The boiling curve shows the changes in the
temperature of a solid as it is converted into a liquid
and then into a gas when the solid is heated
A
B C
D E
F
(A) to (B) heating of solid
• As solid is heated, its temperature increases
• Solid particles absorb more heat energy which is then converted to kinetic energy
• Particles vibrate more vigorously
(B) to (C) Melting (solid to liquid)
• Heat energy absorb by the particle allows them to have sufficient heat energy to overcome the forces of
attraction holding them together
• hence, the particles lose their fixed position and closely packed arrangement
• The particles moved further apart from one another and move freely through the liquid
• The temperature remains constant from B to C as melting occurs

18. A
B C
D E
F
(B) to (C) Melting cont’d
• Heat energy supplied is absorbed by the particles and used to overcome the inter-particle forces of atraction
betwen them instead of being used to increase their temperature
• A pure solid always melts at a fixed temperature
(C) melting is completed. The change in state from solid to liquid is completed
(C) to (D) heating of liquid
• Continous heating causes the temperature to rise
• Liquid particles absorb more heat energy which is converted into kinetic energy. This causes them to move
faster
Boiling is the process whereby its state changes from liquid to gas at its boiling point

19. A
B C
D E
F
(D) to (E) boiling
• At point (D), the heat energy absorbed by the liquid allow them to have sufficient kinetic energy to vibrate
and overcome the interparticles forces of attraction holding them together
• As a result, they lose their closely packed arrangement. And become even further apart
• During boiling , the substance exists as both in the liquid and gas states
• The temperature remains constant from (D) to (E) as boiling occurs
• This temperature correspond to the boiling point of the substance. The heat energy supplied is absorbed by
the particles and is used to overcome the interparticles forces of attraction betwen them instead of increasing
the temperature
• A pure liquid always boil at a fixed temperature
(E) to (F) boiling is completed
• At E, the change in state from liquid to gas is completed
• As the gas continues to be heated, it absorbs more heat energy and its temperature increases

20. Interconversion of State of Matter -Cooling Curve
The cooling curve shows the changes in the
temperature of a gas as it is converted into a liquid
and then into a solid when the gas is cooled
(A) to (B) cooling of gas
• As the gas cooled, it loses heat energy and its temperature decreases
• The kinetic energy of the particles therefore decreases and they move around slower
Condensation is the process whereby a substance changes its state from gas to liquid
(B) to (C) condensation
• At point B, the kinetic energy of the gas particles is insufficient to overcome the interparticles forces of
attraction between them
• As a result they move around less freely and become more attracted to one another, forming an irregularly
packed arrangement
• During condensation, the substance exist in both the liquid and gas state
?
?

21. (C) condensation is completed.
• At C, the change in state from gas to liquid is completed
(C) to (D) cooling of liquid
• As the liquid is cooled, its temperature decreases and its particles loses heat energy
• The kinetic energy of the liquid particles therefore decreases and they move around slower
(D) to (E) freezing
• At D, the kinetic energy of the gas particles is insufficient to overcome the interparticles forces of attraction
between them
• As a result they move around even less freely and begin to settle into fixed positions in a closely packed
regular arrangement
• During freezing, the substance exists in both the liquid and solid state
• The temperature remains constant from (D) to (E) as freezing occurs. This temperature correspond to the
freezing point and melting point of the substance.
• A pure liquid always freezes at a fixed temperature
?
?

22. (E) to (F) Cooling of a solid
• At E, the change in state from liquid to solid is completed
• The solid particles are only able to vibrate about their fixed positions.
• As the solid continues to be cooled, it continues to lose heat energy and its temperature decreases
(E) sublimation
• Sublimation is the process whereby a substance changes its state from solid to gas directly without going
through the liquid state
• During sublimation, solid particles, at the solid surface gain enough kinetic energy to overcome the
interparticles forces in a solid arrangement to become a gas directly
(F) deposition
• deposition is the reverse process of sublimation whereby a substance changes its state from gas to solid
directly without going through the liquid state
• During deposition, gas particles lose enough kinetic energy to settle into a regular fixed arrangement of a
solid directly
?
?

23. Diffusion

24. Diffusion
Definition
• Is defined as a movement of
particles from a region of
higher concentration to a
region of lower concentration
• Diffusion only takes place in
liquid and gases because
their particles are able to
move freely
• Diffusion is faster in gases
than in liquid
Examples
• Propogation of of fragrance
or odours from a source to
an entire room
• Movement of tea particles
from tea bag to teh entire
cup of water without strirring
• Shrinking of a helium ballon
as helium leaves the balloon
through diffusion
Factors
affecting rate
of diffusion
• Relative Molecular Mass
Particles with higher Mr move
more slowly and takes a
longer time to diffuse
• Temperature
Increasing temperature
increases the kinetic energy
and allow them to move faster
• Concentration gradient
A greater concentration
gradient difference between 2
regions will lead to greater
rate of diffusion

25. Worked example