AMKSS Prelim P3 Ans

1 ANG MO KIO SECONDARY SCHOOL PRELIMINARY EXAMINATION 2024 SECONDARY FOUR EXPRESS MARKER REPORT Ques Answer Marks 1(a) (FAN SPEED = 5) TA is measured to 1 dp in oC. (Range: 29.5 – 31.5 oC) 1 TB is measured to 1 dp in oC. (Range: 29.5 – 31.5 oC) 1 Common errors are 1 dp not written and missing or incorrect unit Deduction of only 1 mark if both sets have the above error 1(b) TA (MAX) is measured to 1 dp in oC (-1 from (b) if below 60 oC) 1 TB (MAX) is measured to 1 dp in oC (81) 1 Common error is TA is recorded less than 60 oC 1(c) 3.5 - 4.4 min (4 mins) t is measured to 1 dp in s. AND between 209.5 – 264.4 s Common error to 1 dp not written as qns already stated 4 mins so allowance of few seconds is expected due to human reaction. 1 1(d) TA (4MIN) is measured to 1 dp in oC. (Range: Drop of about 9.5 oC) 1 TB (4MIN) is measured to 1 dp in oC. (Range: Drop of about 15 oC) 1 Mark according to students’ answer. (A or B) Common errors - answer was written as TB or TA instead of A or B - answer was not tailored to the lower temperature drop Diligent pupils showed the difference in drop for both thermometers as a form of checking. 1 1(e) If B drops less: (1) A cool down more due to the cooling effect brought upon by evaporation near the surface of water in test tube. (2) Since the bulb is below water, the water at the bottom loss energy slowly due to the insulating effect of water. So, B cools down less. (3) Since the hot water is poured into A first, A has more time to cool, hence, B drop less (or A drop more) If A drops less: (1) The warmer water with lower density will float to the top where the bulb of the thermometer is. Hence, A will measure a higher temperature and hence, lower temperature drop. (2) As one could not read two thermometers at the same time, B is allowed to cool for a longer time. Hence, B drops more. (3) Thermometer B is fully submerged; more energy will conduct to bulb of thermometer. Hence, the temperature in B will cool down more. (4) Condensation of steam vapour around bulb A and releasing energy to the bulb. Hence, A drop less. Many pupils did not indicate the specific thermometer for explanation. Answers written not close to above ans key will not be given any marks. 2

2 Qns 2 Answers & Remarks Marks (ai) I = 0.14 A (2 d.p.) , 0.13, 0,10 1 (aii) V = 1.65 V (2 d.p.) , 1.70, 1.50 1 (aiii) R = 𝑉 /𝐼 = 1.65 / 0.14 = 11.8  Accepted Range: 11 to 15  Any range not within accepted values will not be given any mark Few pupils even subtracted 1  in the final answer. 1 (bi) D = (0.285+ 0.285) /2 = 0.285 mm No records of more than one reading will not be given any mark 1 (bii)  = 𝜋𝑅𝐷 2 / 4𝐿 = 𝜋 × (13.6) × (0.29 ×10−3) 2 / 4 × 0.800 𝑚 = 1.12 × 10-6  m (actual = 1.10 × 10-6  m for nichrome wire swg32) must have unit  m - Disappointing presentation as many pupils put inconsistent units (