AISS 2023 Sec 3 Express WA1 Answers

1 AHMAD IBRAHIM SECONDARY SCHOOLTERM 1 WEIGHTED ASSESSEMENT 1 2023 Sec 3 Express Pure Chemistry 6092Marking SchemeSection A (10m)12345678910BBCBACCBDCStructured Questions (20m)QnAnswersMarks1(a)B 11(b)1gaseous state [drawn far apart]1(c)At 0°C, the liquid particles are closely packed in disorderly arrangement and slide across one another.As it is cooled down to -114°C, freezing occurs. Particles lose enough energy to become closer together. Up till -120°C, the particles are very closely packed in an orderly manner and vibrate and rotate at fixed position. 111(d)As the temperature increases, the liquid particle of ethanol gains thermal energy and is converted to kinetic energy / start to move faster.At 78°C / boiling point, the particles gain sufficient energy to overcome the forces of attraction between the particles. At 100°C, the gas particles of ethanol are now spread apart / far apart and can move about in any direction. 1111(e)(i)2

2 (1) Filter Funnel(2) Residue / plastic pieces(3) Filtrate / liquid mixture All components must be drawn and labelled correctly1m – Set up drawn correctly [filtration set-up]1m – All 3 components labelled correctly1(e)(ii)Fractionating Column11(e)(iii)Water, it has the highest boiling point of 100°C and is collected last.1Total: 11M2(a)To prevent the sample spot from dissolving into the solvent.12(b)(i)Xanthophyll and chlorophyll has similar solubilities in propanone solvent.12(b)(ii)Use a longer piece of filter paper (to allow the components to move a longer distance.)12(c)11.5120.958fR 12(d)Let the distance be a.120.91210.8faRaaspot to be drawn on filter paper X at 10.8 cm mark. (Near to 11 cm)1Total: 5M3(a)1. She should not add water to the mixture in step 1. She should add ethanol instead. 2. She should not wash the crystals with warm water in step 6 as the crystals may dissolve in warm water. She should wash the crystals with cold water instead.11

3 correct mistake and rectification to obtain 1 mark. 3(b)At higher temperature, the particles gained more energy and move faster, and diffuse at a faster rate from a region of higher concentration (from the teacher) to lower concentration (to other parts of the classroom).11Total: 4MSetter: Mrs Silia Goh