Home › SPM Science › Archive for Energy and Chemical Changes

Energy and Chemical Changes

5.4.3 Extraction of Metals from their Ores Using Coke

Posted on by

5.4.3 Extraction of Metals from their Ores Using Coke

1. In industries, metal ores which are less reactive than carbon are heated with carbon to obtain pure metal.
2. Pure metals which can be extracted using carbon are zinc, iron, tin and lead.

Extraction of Tin from its Ore


Extracting tin ore in a blast furnace
 
1. Tin ore exists naturally as cassiterite (or tin oxide).
2. Tin ore is washed with water to remove sand, clay and others impurities.
3. After that, tin ore is roasted to take away foreign matter such as carbon, sulphur and oil.
4. Lastly, the tin ore is mixed with carbon and limestone in the form of coal and is heated in a blast furnace at a high temperature.
5. The function of the limestone is to remove impurities.
6. Reduction reaction occurs during heating, carbon which is more reactive that tin removes oxygen from the tin oxide to produce pure tin and carbon dioxide.


7. Pure tin flows out from the furnace into moulds to harden as tin ingots.
8. At the same time, the limestone (calcium carbonate) breaks down to form quicklime (calcium oxide) which reacts with impurities to form slag. 

5.9.4 Electrolysis (Structured Questions)

Posted on by

Question 1:
Diagram 1 shows the setting up of apparatus in an experiment.
(a) Name the process in Diagram 1. [1 mark]



(b)(i) Name metal Q. [1 mark]
  
(ii) What happens to metal Q during the process in Diagram 1? [1 mark]

(c) Which metal functions as the cathode? [1 mark]

(d)(i) What will happen to the iron key at the end of the experiment? [1 mark]
 
(ii) State one method to get a good result in (d)(i) [1 mark]


Answer:
(a) Electroplating

(b)(i) Copper
(b)(ii) Metal Q dissolves in the copper(II) sulphate solution to form copper ions and becomes thinner.

(c) Iron key.

(d)(i) The surface of the iron key will be coated with a brown layer of copper.
(d)(ii) The surface of the metal to be plated must be cleaned with sandpaper before electrolysis begins.

5.9.3 Application of Reactivity Series of Metals (Structured Questions)

Posted on by

Question 1:
Diagram below shows the extraction of tin ore at high temperature in a blast furnace.


(a) Name two elements in R. [2 marks]

(b) State one reason why carbon is a suitable element to use in the extraction of tin ore from R? [1 mark]

(c) Name gas S. [1 mark]

(d) What is the function of limestone in this process? [1 mark]

(e) Name product T. [1 mark]


Answer:
(a) Tin, oxygen

(b) As tin is less reactive than carbon, carbon can be used to reduce the tin ore from R.

(c) Carbon dioxide.

(d) The limestone is decomposed to produce quicklime (calcium oxide) which combines with impurities such as silica to form slag.

(e) Slag
 

5.9.2 The Reactivity Series of Metals (Structured Questions)

Posted on by

Question 1:
Diagram 1.1 and Diagram 1.2 show an experiment to study the reactivity of metals with water.



(a) Observe Diagram 1.1. State the volume of gas collected.
  Write down your answer in Table below. [1 mark]


(b) Based on the result in Table above, state one inference. [1 mark]

(c) State the variables in this experiment.
(i) Constant variable [1 mark]
(ii) Responding variable [1 mark]

(d) Based on this experiment, mark (\/) the metal which is more reactive. [1 mark]
Sodium    Calcium  


Answer:
(a)

(b) A reactive metal can displace more gas from water.

(c)(i) The mass of the metal / The time taken

(c)(ii) The volume of gas collected

(d)
Sodium    ∨ Calcium  

5.9.1 Heat Change in Chemical Reactions (Structured Questions)

Posted on by

Question 1:
Diagram 1.1 and Diagram 1.2 show an experiment to study the heat change in chemical reactions at room temperature.



(a) Based on Diagram 1.1, what is your observation about the change in temperature?
  Mark (\/) for your answer in Table below. [1 mark]


(b) What is the final reading for the thermometer in Diagram 1.2? [1 mark]

(c) State the variables in this experiment.
(i) Constant variable [1 mark]
(ii) Responding variable [1 mark]

(d) State one hypothesis for this experiment. [1 mark]


Answer:
(a)

(b) 35 oC

(c)(i) The amount of water or initial temperature

(c)(ii) The final temperature

(d) In a chemical reaction, heat is given out causing a rise in temperature or is absorbed causing a drop in temperature.


5.5.3 Electrolysis of Molten lead (II) bromide

Posted on by

5.5.3 Electrolysis of Molten lead (II) bromide

1.   Figure above shows the apparatus set up for electrolysis of molten lead (II) bromide.
2.   Lead (II) bromide powder in a crucible is heated.
3.   The electrolysis process start when le an (II) bromide start melting.
4.   At the Cathode
When electricity is flowing, a silvery deposit of lead metal forms on the cathode.
5.   At the Anode
When electricity is flowing, brown fumes of bromine gas are seen at the anode.
 
Explanation:

 
 
6.   Thus, electrolysis of lead (II) bromide produces lead and bromine gas.
 
 

5.5.2 Electrolysis of Copper (II) Chloride Solution

Posted on by

5.5.2 Electrolysis of Copper (II) Chloride Solution




1. Electrolysis of copper (II) chloride solution.
(a)  Copper (II) ion with positive charge will attract to cathode to discharge as a copper.
(b)  Chloride ion will attract to anode to discharge as a chlorine gas.
(c)  At anode, chloride ions lose electrons. Greenish gas which can bleach the litmus paper is produced.
(d)  At cathode, copper (II) ion receives electron. Brown solid deposited on the surface of the electrode.
  


2.   Thus, electrolysis of copper (II) chloride produces copper and chlorine gas.
 

5.5 Electrolysis

Posted on by

5.5 Electrolysis
 
5.5.1 Electrolysis
1. Electrolysis is a process where a compound is separated into its constituent elements when electric current passes through an electrolyte.
 
2. In electrolysis, energy is changed as shown below:
Electrical energy → chemical energy

3. The apparatus used in an electrolytic cell consists of a dry cell or battery, an electrolyte and two electrodes as shown below.


Electrolytic cell


Electrolyte
(a) An electrolyte is a compound in a molten form or in aqueous solution which conducts electric current.
(b) Electrolyte contains two types of charged ions which move freely:
 (i)  Ion with positive charge (cation), for example, metal ions and hydrogen ions.
 (ii) Ion with negative charge (anion), for example, non-metal ions.
(c) Example of electrolyte: molten potassium chloride and hydrocloric acid.
 
Electrode
(a) Electrode is a conductor which is immersed in an electrolyte and connected to an electric source.
(b) Examples of electrode: carbon (graphite) and platinum.
(c) The electrode connected to the positive terminal of the cell is positive electrode and is given a name, anode.
(d) The electrode connected to the negative terminal of the cell is negative electrode and is called the cathode.
 
Ammeter
Ammeter is used to detect the flow of current in the circuit.
 
Dry cell or battery
The source that generates electrical energy.

5.4.2 Reactivity Series and Extraction of Metals

Posted on by

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.