Primary 6 PSLE Science Practice Paper 3

TuitionGoWhere Practice Paper - Science Primary 6 PSLE

Answer Key and Marking Scheme Version 3 of 5

Section A: Multiple-Choice Questions (28 marks)

Each correct answer: 2 marks. No working required.

Section B: Open-Ended Questions (72 marks)

15. (a) Any two from: vein pattern (parallel vs. net-like); leaf shape (long and narrow vs. broad and oval); leaf edge (smooth vs. toothed) [1 mark each, max 2]

(b) Rose [1]

(c) Explanation: Using more than one characteristic makes classification more reliable because it reduces the chance of mistakes [1]. If only one characteristic is used, two different types of leaves might happen to share that one feature by chance and be wrongly grouped together [1]. Multiple characteristics help to distinguish more precisely between different types.

Marking notes: Must mention "reduce chance of error/mistake" or "more accurate" [1] and explain why (e.g., some leaves might share one feature by coincidence) [1].

[Total: 5 marks]

16. (a) Any two from: mangrove trees; algae [1 mark each, max 2]

(b) Example: Mangrove trees → caterpillars → small fish → larger fish → monitor lizard / large birds of prey [2]

• Must have 4 organisms including producer and tertiary consumer
• Must show correct sequence with arrows or stated "→" direction

Marking: Correct sequence with producer first, consumer levels increasing [2]. Minor error in sequence [1].

(c) Explanation: If prawns are removed, larger fish lose one food source [1]. The population of larger fish would decrease because there is less food available for them to survive and reproduce [1].

[Total: 6 marks]

17. (a) (i) Material R [1]; Explanation: It is hard (durable, not easily broken) and allows light to pass through (transparent, can see through) [1]. Both properties needed for a window.

(ii) Material Q [1]; Explanation: It is soft (comfortable to wear) and floats in water (helps the swimmer stay afloat/safe) [1]. Both properties needed.

(b) No, the student is not correct. [1] Material P is hard but sinks, and Material R is also hard but sinks—both hard materials sink. However, Q is soft and floats, and while there is no hard material that floats in this table, the student made an absolute claim ("always") which cannot be proven from this limited data, and more importantly, hardness and floating are independent properties. Actually, from the table: P is hard and sinks, R is hard and sinks. No counterexample of hard + floats exists in table, BUT the claim is "always"—we need to say the data does not support "always" as a general rule, OR if interpreting strictly: the student is wrong to generalise from limited examples. Better answer: "The student is not correct. Although all hard materials in the table sink, this does not prove that all hard materials always sink. Also, floating depends on density, not hardness."

Revised marking: Student is not correct [1]. Reason: The table only shows four materials—this is not enough to make a general rule about all materials [1]. OR: Hardness is about how easily something is scratched; floating depends on whether the material is less dense than water. These are different properties.

[Total: 6 marks]

18. (a) Any one from: Seed A has two cotyledons / Seed B has one cotyledon; Seed B has endosperm / Seed A does not have endosperm; Seed A is kidney-shaped / Seed B is more elongated [1]

(b) Seed A: dicot [1]; Seed B: monocot [1]

(c) Explanation: The stored food provides energy/nutrients for the young plant/embryo [1] until it can make its own food through photosynthesis (when leaves develop and reach light) [1].

[Total: 5 marks]

19. Example classification (other valid schemes accepted):

Property used: Ability to conduct electricity / Magnetic properties / Transparency / Flexibility [max 1 if appropriate]

Example by magnetic property:

Group 1 (Magnetic materials): metal spoon, iron nail (not in list—use steel fork), paper clip not in list—correction using given items: [2]

• Actually from list: metal spoon (if contains iron), steel fork, aluminium foil (not magnetic)—need to be careful.

Better classification by origin:

Property: Source (plant vs. animal vs. synthetic/man-made)

Actually better: By electrical/thermal conductivity or By transparency or By whether they come from living things

Example by transparency:

Group 1 (Allows light through/transparent): glass cup [2] Group 2 (Does not allow light through): wooden spoon, metal spoon, plastic spoon, ceramic cup, paper napkin, aluminium foil, cotton towel, rubber band, steel fork [2]

No—only one transparent item.

Better: By material type/source:

Property used: Whether the material comes from a natural or synthetic source [stated clearly] [1]

Group 1 (Natural materials): wooden spoon, cotton towel, paper napkin [2] Group 2 (Synthetic/man-made or processed materials): metal spoon, plastic spoon, glass cup, ceramic cup, aluminium foil, rubber band, steel fork [2]

Or by hardness:

Property: Hard vs. Soft

Group 1 (Hard): metal spoon, glass cup, ceramic cup, aluminium foil, steel fork [2] Group 2 (Soft): wooden spoon, plastic spoon, paper napkin, cotton towel, rubber band [2]

Explanation: This property is useful because it helps decide what the material can be used for [1]—hard materials are durable for tools and containers, soft materials are suitable for items that need to be flexible or gentle [1].

Marking notes: Any valid property with consistent grouping accepted. Must have property stated [1], two correct groups [2 each max], and useful explanation linking property to practical use [2].

[Total: 6 marks]

20. (a) X: stamen (accept: male reproductive part/androecium) [1] Y: ovary [1]

(b) Explanation: Brightly coloured petals attract insects [1]. Insects are attracted to the colour and will land on the flower, picking up pollen and transferring it to another flower (pollination) [1].

(c) Explanation: The fruit protects the seeds inside it [1]. Animals are attracted to eat the fruit, and the seeds pass through their digestive system unharmed, being deposited elsewhere with droppings that provide nutrients for growth (seed dispersal) [1]. OR: The fruit may have hooks, wings, or be light to be carried by wind/water, spreading seeds to new areas.

[Total: 6 marks]

21. (a) Conclusion: Only materials made of iron or steel (which contains iron) or nickel are magnetic [1]. Not all metals are magnetic (copper, aluminium, tin are not attracted) [1].

(b) Method: The chef should move a magnet through the mixture or use a magnet to attract the metal bottle caps from above [1]. The magnetic caps (made of steel/iron) will stick to the magnet and can be removed [1]. The aluminium foil wrappers will not be attracted and will remain behind [1].

Marking notes: Method described [1]; magnetism of steel/iron caps explained [1]; non-magnetic property of aluminium explained [1].

(c) Any one from: Finding if jewellery is genuine gold/silver (not magnetic) vs. fake (may contain magnetic metals); sorting recyclable metals; checking if a pipe/cable contains steel; magnetic door catches; fridge magnets identification [1]

[Total: 6 marks]

22. (a) Explanation: Both the King cobra and Monitor lizard have dry, scaly skin [1]. They are both reptiles, which is the group of vertebrates characterised by having scaly skin and laying eggs with tough shells on land [1].

Marking notes: Must mention "scaly skin" or "dry skin" [1] and "reptiles" as the group [1].

(b) Any two from: give birth to live young (most mammals, though some lay eggs—accept in P6 context); feed young with milk from mammary glands; have hair or fur on body; are warm-blooded [1 each, max 2]

(c) Explanation: The claim is incorrect because the Monitor lizard can swim well but it is a reptile, not a fish [1]. Also, the Great egret (bird) and Malayan tiger (mammal) may swim, and they are not fish. The Malayan tiger or Great egret being vertebrates that can swim but are not fish shows the claim is false [1].

[Total: 6 marks]

23. (a) Permeability / ability to let water pass through / drainage / water-holding capacity [1] (accept "how fast water passes through soil")

(b) Explanation: This is to make it a fair test [1]. If different amounts of water or different funnels were used, we could not compare the results fairly because the amount of water collected would depend on these differences rather than just the soil type [1].

(c) Sandy soil (Funnel C) [1]. The results show that sandy soil let the most water through (approximately 180 ml collected), meaning it is the most permeable/well-drained soil [1].

[Total: 5 marks]

24. (a) (i) small intestine [1] (ii) large intestine [1]

(b) Adaptations of small intestine for absorption:

• It is very long (about 6 metres), giving a large surface area for absorption [1]
• It has millions of tiny finger-like projections called villi, which increase the surface area even more [1]
• Each villus has a network of blood capillaries close to the surface so digested food can pass quickly into the blood [1]

Marking notes: Any three valid points, [1 each, max 3]. Also accept: thin walls (one cell thick) for easy diffusion; constant movement (peristalsis) to mix food with enzymes.

[Total: 5 marks]

25. (a) Explanation: Both yeast and bread mould are fungi because they do not make their own food (they are decomposers/saprophytes), they feed on dead organic matter, and they reproduce by spores [1]. They do not have chlorophyll and are not plants [1].

Marking notes: Must mention "feed on dead matter/decomposers" or "spores" or "no chlorophyll" [1 each, max 2].

(b) Useful: Use clean containers and warm milk to grow yoghurt with Bacterium X (lactobacillus) [1]. Prevent harmful: Brush teeth regularly to prevent tooth decay; limit sugary foods that feed bacteria causing decay [1].

Marking notes: One valid point for encouraging useful effect [1]; one valid point for preventing harmful effect [1].

(c) Explanation: Different micro-organisms produce different useful substances [1]. By understanding this diversity, scientists can select specific micro-organisms (like bacteria or fungi) that produce medicines such as antibiotics, which help treat diseases and improve human health [1].

[Total: 6 marks]

26. (a) Any two valid differences:

• Root hair cell has no chloroplasts; leaf cell has many chloroplasts [1]
• Root hair cell has a root hair projection; leaf cell is more rounded/does not have root hair [1]
• Root hair cell is elongated; leaf cell is more irregular/rounded in shape [1]

(b) Difference 1 explanation (chloroplasts): The leaf cell needs chloroplasts to carry out photosynthesis (make food) using sunlight [1]. The root hair cell is underground and cannot receive light, so it does not need chloroplasts [1].

Difference 2 explanation (root hair): The root hair increases the surface area of the root cell enormously [1]. This allows more water and mineral salts to be absorbed from the soil into the plant [1].

OR Difference 2 explanation (shape): The elongated shape of the root hair cell pushes it between soil particles, helping it reach water in the soil [1]. The more rounded leaf cell shape allows many cells to be packed together to form a flat surface for light absorption [1].

Marking notes: Difference stated [1 each, max 2]; explanation linked to correct function [2 each, max 4]. Marked as pairs.

[Total: 6 marks]

27. (a) X: evaporation (accept: transpiration if referring to plants, but from ocean it's evaporation) [1] Y: condensation [1]

Actually, "water turning to water vapour" from ocean surface = evaporation [1] "water vapour forming clouds" = condensation [1]

(b) Importance of water cycle for living things:

• Provides fresh water for organisms to drink and use [1]
• Water is needed for photosynthesis in plants, which produces food and oxygen for ecosystems [1]
• Distributes water around the Earth so all ecosystems have access to water, not just areas near oceans [1]

Marking notes: Any three valid points about water availability for life processes, [1 each].

(c) Any one from: Cutting down forests reduces transpiration; building dams changes water flow and evaporation; pollution contaminates water making it unusable; climate change alters evaporation and precipitation patterns; urbanisation with concrete surfaces reduces water absorption and increases runoff [1]

[Total: 6 marks]

28. Investigation description:

Equipment: Quadrat (frame of known size, e.g., 1m × 1m), string/markers to mark out areas, identification guide/field guide for plants, tally counter or notebook, calculator [1]

What to measure: Count the number of different types/species of plants in each area. Can also estimate abundance (how many of each type) or percentage cover [1]

Fair test:

• Use the same size quadrat in both areas [1]
• Take the same number of samples/quadrats in each area (e.g., 5 quadrats in field, 5 in garden) [1]
• Sample randomly (place quadrats without choosing where plants look most diverse) to avoid bias [1]

Presenting results:

• Draw a table showing plant species found and their frequency/abundance in each area [1]
• Calculate and compare the species richness (number of different species) for each area
• Could draw bar charts comparing number of species

Sample marking breakdown:

• Equipment mentioned [1]
• Measurement clearly stated (count types/species) [1]
• Fair test: same quadrat size and same number of samples [1]; random sampling mentioned or explained [1]
• Results presentation (table and/or graph mentioned) [1]

[Total: 5 marks]

Mark Summary

END OF ANSWER KEY