Acing PSLE Science
- 1. Avoid Meandering Essays. Use Breadcrumbs? • What’s wrong with meandering essays? - you may end up missing important points, or worse go off course! - you may insert unrelated facts and penalized - you waste valuable time • What’s a breadcrumb? - like Hansel and Gretel, they used breadcrumbs to lead them home, you can also use breadcrumbs to make sure you never lose your way and arrive at the ultimate answer • For example we present this question: “Mei observed that her fish appear to have more gill movements during hot days. Why do you think this happens?” • Instead of jumping in to start frantically splashing in the water, it is prudent to chart your course so that you can swim in a straight line to your destination. • So we can construct a breadcrumb like this: hot day => water temp => O2 dissolved in water => more water to get sufficient O2 => more gill movements then write the answer as such: “On hot days, the water temperature would be warmer and be less able to dissolve oxygen. Therefore to get the sufficient oxygen into its blood stream, the fish needs to move its gills more in order to get more water over its gills.”
- 2. How Many Points Should I Write? • You may be unsure if a 1 mark question requires 2 points or 1 point – just as this example here on the right • Always think whether these are ½-mark + ½- mark answers first and foremost – prepare 2 possible answers and then judge if the 2nd answer is necessary or simply repetitive • Here the obvious answer would be: “The materials X, Y, Z are good insulators.” • But is it enough to answer the question in a practicable way? We then venture further “They are placed in the walls to reduce heat loss from inside the house to the surroundings during winter thereby keeping the house warm; and reduce heat gain from the surroundings into the house during summer thereby keeping the house cool.” • Is the 2nd part essential? The answer would have to be YES! because people don’t stuff things into their walls just because they are good insulators – it has to serve a purpose!
- 3. Always Include A Scientific Principle In Your Answers • In PSLE you are always judged on whether you understand and are able to apply scientific principles • So it is not sufficient to describe phenomena and leave out the scientific principle involved • Consider the diagram on the right, if the question was “Why does the plant grow towards the hole?” • An insufficient, purely observing statement might be: “So that it can get more sunlight.” • The full answer would be: “So that the plant can obtain more sunlight in order to photosynthesize to make food in order to survive and grow.” • So if you find an answer that somehow seems to be short of a “scientific statement” you have to think a little harder.
- 4. Don’t Guess! Quick Sketch To Put Things Into Perspective. Be Sure! • This is especially applicable for questions regarding melting/boiling points e.g. If Martian temperatures range between -153 to +20 degrees Celsius, what gases are in solid form during Martian nights?
- 5. Cut Out The Confusion • To get rid of the confusion, we do this: • Denote True = T, False = F, Correct = C, Incorrect = IC • Place next to each choice to the answers (like above) • The answer is very evident as your mind does not have to perform “double deduction” • There will be questions which ask which answer is Incorrect or False (negatives). A common confusion arises when a student attempts to put a ✓ or a ✗ next to the answers for example: Which of the following are false: 1. rhinos eat ticks on tickbirds 2. tickbirds help the rhinos get rid of ticks 3. tickbirds and ticks fight for food 4. rhinos are harmed by ticks We see that A1 and A3 are false and are tempted to place a ✗ next to them and inadvertently answer A2 and A4 because the ✗ easily tricks the mind during the stress of the exam.
- 6. “Vandalize” The Worksheet! Go Ahead! • Circle the correct answers firmly • Strike out the incorrect answers firmly, including the Answer Number 1, 2, 3, 4 • Why including the Answer Number? In the heat of the exam, you want to glance and be sure you are making the right choice as quickly as possible • Leave no room for the need to back-track • A quick glance will reveal the answer quickly and surely • Many students read through all the choices and by the time they reach the last statement they would have had forgotten the first • This leads to wasted time and leaves plenty of room for error • Sometimes after working out the right answer, a student often marks down the wrong answer in the space of 1 second!!!
- 7. Learn How To Connect The Dots • Learn to sketch out a simple diagram which can possible connect the 2 sets of information • Many deductive questions present 2 sets of information and asks for the combined result • Students stumble because they think of the information as 2 distinct and disconnected sets
- 8. Use All Data Given! • It’s a highly rare occurrence in PSLE level exams that data are not usable • So any data that are provided SHOULD be used as far as possible! • Here the usable information are: - yeast can reproduce with sugar solution - equal amounts are used in 5 tubes - different temperatures used - chart of CO2 vs Temp • An incomplete answer could be: “He was trying to find out if heating the water will produce carbon dioxide.” • A complete answer would be: “We was trying to find out how the different temperatures affect the amount of carbon dioxide produced by the reproducing yeast.” • Why is “reproducing yeast” important? It is required to demonstrate that you understand that yeast respire to produce CO2 and more yeast = more respiration = more CO2.
- 9. State The Ultimate Observable Result • Many Section B questions demands that you note only explain the phenomenon but state the ultimate result which must be observable • When is the UOR required? • Usually the question starts with “Explain why (something happens)” or “What happens when (something else)” • For example: “What happens when the farmer sprays insecticide on his crops” • An insufficient answer would be: “The insect pests would be killed.” • A sufficient answer would be: “Insect pests would be killed. As the death rate surpasses the birth date of the insect pest population, the population would be reduced (observable). With less pests feeding on the crops, there will be more crops for harvesting (ultimate observable result).” • Above we see an example of an insufficient answer. The phenomenon explained was that the EPE was converted into KE – but that is not an ultimate observable result. Having KE caused the toy to move – that would be.
- 10. Understanding Population • Most students have the simplistic view of population size, expressing it as population increase or decrease without taking into account the dynamics of a population • Forces of increase: abundant food, space and resources lack of competition lack of predator absence of disease Births • Forces of decrease: opposite of above Deaths • If Births > Deaths then the population will increase • In questions regarding food webs and resources it will always be about which Forces are stronger • In the above example, we can see that it would have been insufficient to say that (bi) There was less food for the snake and hence the snake population decreased.”
- 11. Using Direct Factors To Answer • In the negative example above, the student stated that if the number of organisms were not the same in the beginning then the answer would would be unreliable – but that is addressing a “flip side” scenario which is an INDIRECT FACTOR • We need to talk about the DIRECT FACTOR always! • So the answer should have been “To make sure the test is FAIR (1/2marks) so the change in population of aphids can only be due to the TYPE of Organism (1/2marks)” • What is an Direct Factor? It is a factor that is the primary reason for something happening • For example if your teacher asked “Why are you earlier than Kenneth today?” You should not reply “Kenneth was held back by a massive traffic jam.” (INDIRECT FACTOR) but “My car experienced very light traffic all the way to school.” (DIRECT FACTOR)
- 12. Using Direct Factors To Answer – Part 2 • This can be a 2 mark question. • In this experiment its obvious SETUP A’s soup will boil first given all other factors being equal • We should not explain it as such: “SETUP B’s plate in contact with the pot had grooves which contained air which is a heat insulator so the heat was not transferred efficiently to the pot.” (INDIRECT + INSUFFICIENT) (0 marks!) • The DIRECT FACTOR + SUFFICIENT method is required: “SETUP A’s metal plate had a LARGER SURFACE AREA (½ marks) in contact with the pot, and metal being a GOOD CONDUCTOR (½ marks), can transfer the heat quickly (½ marks) to the pot from the fire. (½ marks)” • It is important to mention the source of the heat also hence the ½ marks.
- 13. Simplifying Data 1 • If we do not attempt to simplify the data – we may experience a big mental blog that prevents us from thinking clearly and wastes time • The solution is to chop away pieces of the big scary monster until you are left with a tiny manageable monster you can squash with your toe • The first step is usually to remove clutter, usually data that does not contribute like constants (no change) like the example on the right: - 1st we cancel away all “Soil” since it is a common factor - then we examine each factor “Water”, Light”, “Fertilizer”, “Warmth” and if we find a negative – the entire line goes! - finally the “surviving” line is the one without cancellations
- 14. Simplifying Data 2 • Another way of simplifying is, instead of cancelling, we identify the positive factors • In this example, we circle the correct answers on each column without attempting to go sequentially row by row • The answer is obviously the row that had all the overlaps • This method reduces clutter as well as saves time since you do not have to read all the lines and attempt to compare
- 15. Based On The Diagram… • You may see questions which specifically state, “Based on the picture of this animal which lives in the desert, describe the physiological adaptations it would utilize to survive.” • Even though you know it’s a FENNEC FOX you cannot call it the a “Fennec Fox” – you have to call it “the animal” because its based on your observations which may mislead you into thinking it IS a Fennec fox. • You must also throw away all that you know about Fennec foxes such as the fact that they have kidneys which can retain water to prevent dehydration (you CANNOT see that from the picture!) • So you can only state that “This ANIMAL has blood vessels running though very large ears (1/2 marks) in order to have a large exposed surface area (1/2 marks) in order to transfer heat from the blood to the surrounding air (1/2 marks), thereby cooling the animal in the hot desert (1/2 marks).” • You will also notice that the Ultimate Observable Result is crucially stated here: “… thereby cooling the animal in the hot desert.” Can we observe this? Yes! You can conduct tests to measure the animals body temperature with or without the ears exposed. With is this the “Ultimate Result”? Well the ears are not for Halloween, its to ensure the animal is cool and therefore survives the hot desert – how much more “Ultimate” can you ask for?
- 16. All In The Family In Section B… • Section B long form questions are usually broken into parts • Note that 1 question will have 1 single theme even though it may have different parts which seem to touch on different things • In this example on the right you have to ask yourself what the “Concept” is • If you answered “Heat” it doesn’t work because it cannot be the underlying theme for all 3 parts • If you answered “Energy” it hits the nail on the head because all discuss energy conversions • Other “same questions” may involve related topics like: electricity-magnetism-light light-photosynthesis-transpiration adaptation-mutualism-population
- 17. Final Advice • Some Section A questions only take 20 seconds, some 2.5 minutes to solve – do not panic and think you are way behind time • Try to complete Section A by 25-30 minutes (30 questions) • Try to complete Section B by 40-50 minutes (14 questions) • This should give you about 15-20 minutes to check (must always check!) • If you are unsure about a question circle or mark; attempt your best answer (never leave a blank no matter what) and then come back later – never waste time getting stuck at a question because you can get a lot more points moving ahead (its been proven that your subconscious brain can work on a problem even when you are focusing on something else – and give you a better perspective when you next revisit the question!) • Try to take short breaks every 5-6 (you decide? maybe 8-10?) questions in order to “refresh yourself” to maximize the next lap – if you attempt to plow through non-stop you are likely to make careless mistakes • For the short breaks, you can close your eyes, do some neck rotation and deep (silent breathing) this relaxes your mind and gets oxygen into your brain for clarity; do not look around and be panicked by people frantically scribbling around you – if you need to look at something look at the ceiling • You should try to highlight important keywords to get the gist of the question to your brain better • You should scribble and doodle around your answer space in order to help you organize your thoughts – don’t worry as anything not in your answer space will NOT be counted • More lines (in your answer space) will be provided than you will ever need – so if you find that you need to write beyond – its likely you are writing too much; use the breadcrumbs method to shorten and organize your answer better • If you still need more lines – please use a ruler and draw; examiners may ignore words outside • Do not waste your time using correction tape, just cross out words and use arrows to insert words/phrases you need instead of re-doing the entire sentence which wastes a lot of time!
- 18. Possible “Bonus” Questions • These usually involve something Singapore is deeply involved in recently – these are the possible topics. Please read up on them for CAUSES and EFFECTS: • Haze from Indonesia • Prolonged Drought • Severe Storms (ripping out trees) • Gardens By The Bay recycling organic material for fuel and fertilizers • Rising Sea Levels • Green Building Initiatives • Reduce Reuse Recycle campaign