8.7.1 The Abiotic and Biotic Components of the Environment (Structured Question 1 & 2)

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Question 1:
R, S and T in Figure below show three types of interactions between organisms.


(a)(i) Name the type of interaction represented by R and S.

(ii) Describe the interaction represented by R.
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(b)(i) In the interactions represented by S and T, what terms are used to describe organisms X and Y?

(ii) State one characteristics of organism X that adapts it for the interaction.

(c) The rubber tree in the interaction represented by S dies.
Explain what will happen to organism X.

(d) Saw dust can be used in the interaction represented by T for the commercial cultivation of mushrooms.
Explain how mushrooms can grow on saw dust.


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Answer:
(a)(i)
Organism R: Mutualism/ symbiosis
Organism S: Commensalism

(a)(ii)
Nitrogen-fixing bacteria in the root nodules fix nitrogen to form ammonia which is used by the plant while Rhizobium bacteria get shelter from the plant.
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(b)(i)
X: Epiphyte
Y: Saprophyte

(b)(ii)
The presence of aerial roots which absorb moisture from the air

(c)
X continues to grow because it photosynthesises.

(d)
Mushrooms grow on dead organic matter.
Mushrooms secrete enzymes which digest the complex organic matter to simple substances.


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6.2.2 Nuclear Fusion

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6.2.2 Nuclear Fusion
1. Nuclear fusion is a process that two light nuclei combine to form a heavier and more stable nucleus together with the release of a huge amount of nuclear energy.
Nuclear fusion

2. The energy produced by nuclear fusion is safe to use as no radioactive radiation is produced during the process.
 
3. A hydrogen bomb uses the principle of nuclear fusion for its design. A hydrogen bomb releases more nuclear energy than an atomic bomb.
 
4. Fusion is much more difficult to achieve than fission because the hydrogen nuclei repel each other.
 
5. Fusion reactor is not commercially produced because nuclear fusion occurs at a very high temperature and pressure.
 
6. Nuclear fusion only occurs naturally in the sun to release heat energy and light energy.

6.2.1 Production of Nuclear Energy and Its Uses

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6.2.1 Production of Nuclear Energy and Its Uses
Nuclear energy can be produced in nuclear reactors through the following two methods:
(a)  Nuclear fission
(b)  Nuclear fusion

6.2.1 Nuclear Fission
1. Nuclear fission is a process involving the splitting of a heavy nucleus into two nuclei of roughly equal mass and shooting out several neutrons at the same time.


Nuclear fission of uranium to produce nuclear energy


2. Nuclear fission occurs when a high energy neutron bombards a uranium nucleus. The nucleus becomes unstable and splits into two (or more) lighter nuclei with the release of two or three neutrons and a large amount of nuclear energy.
 
3. The nuclear fission can only occur in some types of heavy and unstable nuclei such as uranium-235 and plutonium-239.
 
4. A chain reaction occurs as the process of nuclear fission keeps on repeating. The neutrons produced will bombard more uranium-235. The chain reaction produces more neutrons and releases more nuclear energy.
 
5. Uncontrolled chain reaction occurred when atomic bombs exploded in Hiroshima and Nagasaki in Japan during Second World War. Thousands of lives were lost and properties destroyed.

6.1 (C) Radioisotopes

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(C) Radioisotopes
Radioisotopes are isotopes of a radioactive substance.

Examples of Radioisotopes
Carbon-14 (Carbon dating)
Cobalt-60 (Radiotherapy)
Uranium-235 (Nuclear fuel)
Uranium-238
Plutonium-238
Plutomium-239 (Nuclear fuel)


Uses of Radioisotopes
1.   There are two types of isotopes, namely
a.   the stable isotopes (non-radioactive)
b.   the non-stable isotopes (radioactive).
2.  Unstable isotopes go through radioactive decay and emit radiation and they are known as radioisotopes.
3.  Radioisotopes have many applications in industry.


Uses of Radioisotope in Medical
 
Radiotherapy
Gamma rays of cobalt-60 can be used to destroy cancer cells in patients. This treatment is known as radiotherapy.

Tracer to Detect Blood Clots or Tumour
1.   A small amount of sodium-24 is injected into the patient's body.
2.  Radioactive imaging is then used to detect accumulation of sodium-24 and therefore detect tumours and blood clots before they become dangerous.

Sterilising Medical Instrument
 
 
1.   Gamma ray emitted from radioactive cobalt-60 can kill germs such as bacteria and fungus.
2.  Medical instruments such as surgical equipment, syringes and bandages can be sterilised by using gamma rays.


Uses of Radioisotope in Agriculture
 
Pest Control
 

Male insect is sterilised by exposing to radioactive radiation and then released back to the ecosystem. This can ensure that their reproducing effort do not generate new generation and hence reduces the population of the insect.
 
Tracer
1.   The metabolism of phosphorus by plants can be studied using phosphate fertilisers that contain phosphorus-32.
2.  A small amount of phosphorus-32 is used in fertilisers.
3.  The radiation produced by phosphorus-32 decay is detected by a Geiger-Muller counter. This method can trace the passage of phosphate ions in plants.
4.  Carbon-14 is used to study the passage of carbon during photosynthesis in plants.

Develop New Species of Plant
1.   Radioactive radiation is targeted to the seeds of plants and hence causes mutation to the genes.
2.  By chance, this may develop some superior agricultural products.


Archeology


Radioisotope carbon-14 is used to study and estimate the age of ancient artifacts. This method is named as the radiocarbon dating.



Preserve Food


1. The gamma rays from cobalt-60 are used to kill bacteria in food to make fresh vegetables and fruits last longer without any change in quality, flavour and texture of food.
2.  Gamma rays are used to inhibit budding in potatoes and germinating in onions.


Monitoring Thickness of Steel/paper Sheet


 1. In a factory, the thickness of paper can be controlled by measuring the quantity of radiation penetrating the paper with the Geiger-Muller counter.
2. Apart from paper, the thickness of plastic, aluminium or iron can also be controlled by using beta rays.


Detecting Underground Leakage


1. A small quantity of radioactive substance is put into water, gas or oil in an underground pipe.
2. The movement of the radioactive substance can be traced by using the Geiger-Muller counter.


Monitoring Content of Food

 

1.   Radiation is used for checking whether a food container has the right amount of food stuff.



Measuring the Wearing Rate of Engine
 


6.1(B) Types of Radiation

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(B) Types of Radiation
3 types of radioactive radiation might be released from a nucleus during a radioactive decay, namely
a.   Alpha radiation
b.   Beta radiation
c.   Gamma radiation





Penetrating Power


Deflection in Electric Field
 

















6.1(A) The composition of the Nucleus

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(A) The Composition of the Nucleus

Stability of Nucleus
The nucleus becomes unstable if it has too many protons, too many neutrons or too much
energy.

Radioactive Decay
1.   The unstable nucleus will decay to release radioactive radiation.
2.  Radioactivity is the spontaneous process of an unstable nucleus emitting radioactive
emission in order to become more stable.
 

6.1 Radioactive Substances

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6.1 Radioactive Substances

1.   Radioactive substances are substances with unstable nuclei in their atoms. Unstable nuclei will decay and emit radioactive radiation.
2.  Examples of radioactive substances are:
 (a)  Carbon-14
 (b)  Cobalt-60
 (c)  Iodine-131
 (d)  Uranium

5.9.4 Electrolysis (Structured Questions)

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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)

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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)

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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