XMS SEC 3 WA1 2020 MS

3 S3E 2020 WA1 Answers Section A [5 marks] 1 2 3 4 5 D A B B C Section B [20 marks] B1ai A E 1 1 B1aii B & C 1 B1aiii D (Accept: Magnesium) 1 B1aiv 37 1 B1av Sulfur 1 B1avi 2- OR -2 1 B1bi consisting of oppositely charged magnesium and chloride ions (Accept: oppositely charged ions) held together by strong electrostatic forces of attraction. 1 1 B1bii 1 mark for correct ratio; 1 mark for correct charges; 1 mark for correct number of electrons 3 B2ai 100oC 1 B2aii 250oC 1 B2bi solid 1 B2bii solid + liquid 1 B2biii gas 1 B2c As the temperature increases, the particles gain energy and move faster. When the temperature is high enough, the particles have sufficient energy to overcome the forces of attraction. The particles are spread far apart and can move about rapidly in all directions. 1 1 1 1

4 B3ai 4oC 1 B3aii Kidney: 48 hours Pancreas: 17 hours 1 1 B3bi Hydrogen bonds are formed between the slight positive and slight negative charges on the water molecules. Accept: Hydrogen bonds are a type of weak van der Waals’ force of attraction. 1 B3bii Hexagon/ 6-sided shape/ 6-sided polygon 1 B3biii This is because the cooling of water forces the water molecules to be in an arrangement that would crowd them. To create more space, the cooling water then expands until it reaches freezing point. 1 1 B3c Student C. If the blood was cooled to a lower temperature, the red blood cells may get damaged by the formation of ice crystals and haemoglobin would be lost when the blood is thawed. 1 1