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5.4.2 Reactivity Series and Extraction of Metals

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5.4.2 Reactivity Series and Extraction of Metals

1. The method that is used in the extraction of metal from its are depends on the position of the metal in the reactivity series of metals.
 



2. Metals which are located higher than carbon in the reactivity series are extracted from their molten ores using the electrolysis method.
3. Metals which are located lower than carbon in the reactivity series are extracted using the reduction method with coke (or carbon).
4. Carbon is used in the extraction process because
(a)  It is cheap
(b)  Easily obtained
5. Metals located the lowest in the reactivity series like silver and gold can be extracted naturally without any complex chemical reaction. These metals exist as free elements in the Earth’s crust.

4.9.3 The Properties of Substances (Structured Questions)

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Question 1:
Diagram 1.1 and Diagram 1.2 show an experiment to study the electrical conductivity of lead(II) bromide.


(a)(i) Based on Diagram 1.2, what is your observation on the needle of the ammeter? [1 mark]

(ii) What is the reading of the ammeter in Diagram 1.2? [1 mark]

(b) State the variables I this experiment.
  (i) Manipulated variable:
  (ii) Responding variable:
[2 marks]

(c) State one inference for this experiment. [1 mark]

(d) Lead(II) bromide is an ionic compound.
  State the operational definition for an ionic compound. [1 mark]


Answer:
(a)(i) The pointer of the ammeter is deflected.

(a)(ii) 0.4 A

(b)(i) The state of the lead(II) bromide or chemical compound

(b)(ii) The ammeter reading

(c) Lead(II) bromide in the molten state can conduct electricity.

(d) An ionic compound in the molten state will cause the pointer of the ammeter connected in a closed circuit to be deflected.


4.9.2 Proton Number and Nucleon Number (Structured Questions)

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Question 1:
Diagram 1.1 shows the structure of an atom.

(a) P and Q are subatomic particles.
  Name P and Q. [2 marks]

(b) What is the charge of P? [1 mark]

(c) What is the nucleon number of this atom? [1 mark]

(d) Diagram 1.2 shows the structure of three atoms.
(i) Which atoms are isotopes? [1 mark]
 Mark (\/) your answers in the box provided in Diagram 1.2.

(ii) Based on Diagram 1.2, complete the sentence below.
Isotopes are atoms of an element which have different number of nucleons but the same number of ______________. [1 mark]


Answer:
(a)
P: Electron
Q: Neutron

(b) Negative

(c) 13

(d)(i)

(d)(ii) Protons


4.9.1 Analysing Changes in the States of Matter (Structured Questions)

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Question 1:
Diagram below shows the changes in the state of matter of a substance.
Based on the Diagram,
(a) name the processes R, S and T using the following information. [3 marks]



(b) What happens to the kinetic energy of the particles in the substance during process R? [1 mark]

(c) What happens to the movement of the particles in the substance during process S? [1 mark]

(d) Draw the particle arrangement in X in the box provided below. [1 mark]



Answer:
(a)
R: Melting
S: Freezing
T: Condensation

(b) During melting, the kinetic energy of the particles increases.

(c) During freezing, the particles slowing down in their motion and form a pattern, becoming a solid.

(d)



4.5.2 Classification of Substances

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Classification of Substances

1. Types of substances:


 
2. The physical properties of substances depend on
 (a)  types of particles they contain,
   (b)  arrangement of the particles,
   (c)  forces of attraction between the particles.


Substances made of atoms (or Atomic substances)
1.   Atomic substances are substances that consist of only atoms.
2.   The atoms in atomic substances are arranged closely together in a fixed pattern and only can vibrate in their fixed positions.
3.   Atomic substances have high melting and boiling points owing to strong metallic bond.
4.   They are able to conduct electricity owing to presence of free electrons.
5.   All metals are atomic substances such as iron, aluminium and calcium.


Substances made of molecules (or Molecular substances)
1.   Molecular substances are made up of molecules which have two or more atoms of the same type or different types.
2.   For example, two oxygen atoms combine to form one oxygen molecule. On the other hand, one nitrogen atom combines with three hydrogen atoms to form one ammonia molecule.
3.   Examples of other molecular substances are hydrogen, nitrogen, carbon dioxide, sulphur dioxide, chlorine gas and iodine.
4.   Molecules are held together by weak intermolecular force (or van der Waals forces) and have low melting and boiling points.


5.   Molecules are made up of non-metal atoms which are poor conductors of electricity because there are no free electrons or ions in any state to carry electric charge.


Substances made of ions (or Ionic substances)
1.   Substances that made up of ions are called the ionic compounds.
2.   They are compounds of metal bonded with non-metal.
3.   Examples of ionic compounds are sodium chloride, copper (II) sulphate, sodium hydroxide and lead (II) oxide.
4.   Positive and negative ions are held together by strong ionic bonds. This strong bonding force makes ionic compounds has high melting and boiling points.
 

Arrangement of ions in a compound

5.   All ionic compounds are crystalline solids at room temperature.
6.   The solid crystals do not conduct electricity because the ions are not free to move to carry an electric current.
7.   However, if the ionic compound is melted or dissolved in water, the liquid will now conduct electricity, as the ion particles are now free.

4.5 Properties of Substances Based on their Particle Content

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4.5 Properties of Substances Based on their Particle Content

1.   Matter is anything that occupies space and has mass.
2.   Matter can be divided into elements and compounds.




4.5.1 Atoms, Molecules and Ions
1.   Substances are made of tiny particles called atoms, molecules and ions.
2.   Atoms are the tiniest particles in an element.
3.   A molecule consists of two or more atoms of the same type or of different types that are chemically combined together.
4.   Ions are particles which carry positive or negative charges.




4.4 Classification of Elements in the Period Table

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4.4 Classification of Elements in the Period Table







4.4.1 The classification of Elements

1. In modern periodic table, the elements are arranged in ascending order of proton number.



Group
1. The vertical columns of the periodic table is called group.

2. There are 18 groups in the periodic table.

3. Elements in the same group have similar chemical properties.
Example:
Elements in Group 1 react violently with water to produce metal hydroxide, hydrogen and heat.

4. Elements in groups 1 and 2 are very reactive metals (except hydrogen).

5. Elements between groups 2 and 13 are called the transition elements.

6. Transition elements are metallic elements. Most of them are hard and shiny. All transition elements are good conductors of electricity.

7. The elements in group 17 are non-metals called halogens.

8. Group 18 consists of noble (inert) gases, which are inactive gases.


Period
1. The horizontal rows is called the period.

2. There are 7 periods in period table.

3. The first period has 2 elements only.

4. The second and third period consist of 8 elements, are called the short period.

5. The forth and the fifth period consist of 18 elements, are called the long period.

6. The sixth and the seventh period have 32 elements.

7. The chemical and physical properties of the elements are gradually changed when crossing periods.


4.4.2 Metals, Semi-metals and Non-metals
1. The elements in the Periodic Table are divided into metals, semi-metals and non-metals.

2. Most elements in group 1, 2, 13 and transition elements are metals.

3. Most non-metal elements are located in groups 16, 17 and 18.

4. Seven elements between metals and non-metals are semi-metals. Semi-metals possess certain properties of metals and non-metals.

5. When moving across a period from left to right, the properties of metal change gradually to those of semi-metal and finally non-metal.  

6. The metals become increasingly active as they move down the table.


4.4.3 Importance of the Periodic Table
1. The periodic table enables us to study the elements in an orderly and systematic way.

2. It helps us to know the properties of elements that fall into a particular group.

3. It enables us to predict the properties, reactions and uses of the elements.

4.3.2 Isotopes

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4.3.2 Isotopes

1. Isotopes are atoms of certain elements which have the same number of protons but different number of neutrons in the nucleus of the atoms.



2. Isotopes of the same element have same chemical properties. For example, both carbon-12 and carbon-13 burn in oxygen to form carbon dioxide.
 
3. Physical properties of isotopes are different. For example, carbon-14 isotope has a melting point, boiling point and density that are higher than those of carbon-12 and carbon-13.


Examples of isotopes




4.3 Proton Number and Nucleon Number in Atoms of Elements

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4.3 Proton Number and Nucleon Number in Atoms of Elements

4.3.1 Proton Number and Nucleon Number
1. The proton number represents the number of proton found in nucleus of an atom. Sometime, it is also known as the atomic number.
 
2. Nucleons are the subatomic particles inside the nucleus of an atom,
Nucleon = protons and neutrons
 
3. Nucleon number represents the number of nucleons in an atom.
Nucleon Number = Number of protons + Number of neutrons
 
Example:



4. In a neutral atom contains an equal number of protons and electrons.
 
5. Atoms of certain elements can be represented by the following symbol:
 
  Number of protons = 8
  Number of electrons = 8
  Number of neutrons = 16 – 8 = 8

6. Table below shows the proton number and nucleon number for some elements.
 
Atom
Proton
Number
Nucleon
Number
Amount of
Proton
Amount of
electron
Amount of
Neutron
Helium
2
4
2
2
2
Oxygen
8
16
8
8
8
Sodium
11
23
11
11
12
Chlorine
17
35
17
17
18
 Relationship between the number of subatomic particles, proton number and nucleon number

4.2 Structure of Atoms

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4.2 Structure of Atoms

Atoms
1. All matter consists of tiny units called atoms.
2. Atom is a basic unit of all matter.

4.2.1 Subatomic Particles
1. An atom is made up of particles that are even smaller called subatomic particles.
 There are three types of subatomic particles, which are
 (a)  Protons
 (b)  Neutrons
 (c)  Electrons




Subatomic particles in an atom



4.2.2 Comparison between Subatomic Particles



1. Atoms of any element are neutral because the number of protons and the number of electrons in an atom are the same.
2. In a neutral atom, the number of protons is the same as the number of electrons.