[Physics SPM] Exam Pointers III

Source: Maths & Science Guide

Revision

1. Compare the separating distance between consecutive bright fringes of red light with that of blue light of the interference pattern obtained from a Young's double slit experiment.
   
   
2. State one observation of the interference pattern of red light in a Young's double slit experiment.

Frequent Mistakes

Student's answer:

1. The interference of red light has a bigger number of fringes due to the smaller separating distance compared to that of blue light. This is because the wavelength of red light is bigger than that of blue light.
   
   
2. Bright and dark fringes are observed due to the interference of coherent waves.

Correct Answer

1. The separating distance between consecutive bright fringes of red light is bigger than that of blue light.
   
   
2. Alternate bright and dark fringes are formed. The central fringe is the bright fringe. All the fringe sizes are equal, or the separating distance of consecutive fringes is the same.

[Physics SPM] Exam Pointers II

Source: Maths & Science Guide

Revision

1. What are waves?
   
   
2. What is meant by "speed"?

Frequent Mistakes

Student's answers:

• Waves are energy produced by oscillations that is able to transfer through medium and travel through vacuum.

Correct Answers

1. Waves are the propagation of energy through the oscillation of particles of a medium.
   
   
2. It is the rate of change of distance. It is = (distance/time). When an object travels a distance of 20m in 10s, its speed is (20/10) = 2m/s. It is scalar quantity.

Comments:

• The command phrase is "What is meant". Thus, you can choose to give the definition of speed, OR examples that provide the meaning of speed.

[Chemistry SPM] Chemistry Term & Definition

1. Isomers
   Definition: Compound with the same molecular formula but different structural formulae.
   
   
2. Empirical Formula
   Definition: The formula that gives the simplest whole number ratio of atoms of each element in the compound.
   
   
3. Electrolysis
   Definition: A process that involves passing electricity through compounds in molten or aqueous state to break them down into their constituent elements.
   
   
4. Melting point
   Definition: The temperature at which a solid changes into liquid form under a particular pressure.
   
   
5. Strong alkali
   Definition: A chemical substance that ionises completely in water and produces a high concentration of hydroxide ions.
   
   
6. Unsaturated hydrocarbon
   Definition: An organic compound that contains only carbon and hydrogen, as well as double or triple bonds between carbon atoms.
   
   
7. Redox reaction
   Definition: A reaction that involves electron transfer or a change in oxidation number.
   
   
8. Activation energy
   Definition: The minimum energy colliding reactant particles must have before collisions between them can result in a chemical reaction.
   
   
9. Strong acid
   Definition: A chemical substance that ionises completely in water and produces a high concentration of hydrogen ions.
   
   
10. Rate of reaction
    Definition: The charge in quantity of reactants and reaction products with time.

[Physics SPM] Exam Pointers I

Source: Maths & Science Guide

Revision

1. Relate the inertia of an object to its mass.
   
   
2. Why does refraction of water waves occur?
   
   
3. What is observed when a mercury thermometer is placed in a hot water of 80°C?

Frequent Mistakes

Student's answer:

1. The inertia of an object is directly proportional to its mass.
   
   
2. When a water wave travels from deep water to shallow water, it undergoes refraction.
   
   
3. Themal equilibrium is achieved.

Correct Answers

1. The higher the mass, the higher is the inertia.
   
   
2. Because water waves undergo change in speed in the direction of propagation.
   
   
3. The mercury length increases to the 80°C mark./The mercury rises up the tube to the 80°C mark.

* Deeper water allows greater velocities while shallower water causes lower velocities.

[Physics Form 4] Lighting Up!

1. How are we able to see an object?
   Answer: When enough light falls on the object, incident light rays are reflected from its surface. The reflected light rays then enter our eyes and form an image on the retina. We are able to see the object when the brain interprets the image.
   
   
2. Must light be incident on an object? If objects cannot be seen in a dark room, how are we able to see a lighted bulb in it?
   Answer: A lighted bulb is a primary light source that emits its own light. Hence, its incident light rays directly enter our eyes and form an image. On the other hand, objects that do not emit light rely on the reflected incident light rays to form an image in our eyes. These objects act as secondary sources of light.
   
   
3. Is the moon seen through the reflection of the sun's light that is incident on it?
   Answer: Yes.

[Biology Form 5] Characteristics - Laws of Inheritance

Gregor Mendel is highly attributed for his work in genetics. The father of genetic studied the inheritance of characteristics from the common garden pea plant, Pisum sativum, and was credited with discovering the two basic laws of inheritance: the law of segregation and the law of independent assortment.

1. All characteristics are controlled by pair of genes.
   
   
2. a) A characteristic is a distinctive inherited feature. Three examples of characteristics in:
   
   • Plants - Height of plant, seed colour, seed shape.
   • Animals - Eye colour, height, colour of fur/skin.
   
   b) A trait is a variant for each characteristic. Two examples of traits in:
   
   • Plants - Yellow colour of seed, wrinkled seed shape.
   • Animals - Grey fur colour, green eyes.
   
   
3. A gene is a specific segment of DNA.
   
   
4. Two genes, each found on the same locus along a pair of homologous chromosomes, are needed to determine one characteristic.
   
   
5. Each member of the pair of genes determining a particular characteristic is called an allele.
   
   
6. A dominant allele is one which, when present, even singly, is strong enough to determine the phenotype. The two following conditions can allow a dominant allele to express itself in the phenotype.
   a) Homozygous dominant: two dominant alleles present.
   b) Heterozygous dominant: one dominant allele and one recessive allele present.
   
   
7. A recessive allele can only determine a phenotype if it is present on both homologous chromosomes.

[Biology SPM] Exam Pointers II

Source: Maths & Science Guide

Revision

1. How do you separate blood into plasma and its cells?
   
   
2. Two types of land snails with brown and green shell colours are studied on a grassland habitat covered with dead woods, twigs and fallen leaves. State why quadrat sampling is inappropriate in the above investigation.
   
   
3. Name the substrate on which the enzyme lipase acts.

Frequent Mistakes

Student answers:

1. By centrifuging at high speed for a few minutes, the blood can be separated into plasma and its cells.
   
   
2. Quadrat sampling is time consuming and tedious to carry out.
   
   
3. Fats.

Tutor's comments:

1. A sampling method is chosen based on the animal studied. The student should have made some reference to the land snails.
   
   
2. Fats are a smaller group of a larger family of lipids. Lipids include triglycerides (fats and oils), phospholipids and steroids.

Correct Answer

1. By centrifuging blood at high speed for a few minutes. Subsequently, it separetes into two layers - the plasma layer on top and the cells at the bottom.
   
   
2. Since land snails are mobile organisms, they can move out of the quadrats. Hence, findings based on this technique will not be reliable.
   
   
3. Lipids.