GOZO COLLEGE Secondary School KULLEĠĠ TA GĦAWDEX Skola Sekondarja Half Yearly Exam 015 Year 9 Track 3 CHEMISTRY Time: 1½ hours Name: Class: Useful Data: Atomic numbers and relative atomic masses are given in the periodic table below. The Periodic Table 1 3 4 5 6 7 0 7 Li 3 3 Na 39 K 19 85 Rb 37 133 Cs 55 3 Fr 87 9 Be 4 4 Mg 1 40 Ca 0 88 Sr 38 137 Ba 56 45 Sc 1 89 Y 39 139 La 57 48 Ti 91 Zr 40 178 Hf 7 51 V 3 93 Nb 41 181 Ta 73 5 Cr 4 96 Mo 99 4 184 W 74 Key: 1 H 1 55 Mn 56 5 Tc 43 186 Re 75 Fe 6 101 Ru 44 190 Os 76 a X b 59 Co 7 103 Rh 45 19 Ir 77 59 Ni 8 106 Pd 46 195 Pt 78 63.5 Cu 9 108 Ag 47 197 Au 79 relative atomic mass symbol atomic number 65 Zn 30 Cd 48 01 Hg 80 B 5 7 Al 13 70 Ga 31 5 In 49 04 Tl 81 1 C 6 8 Si 14 73 Ge 3 9 Sn 50 07 Pb 8 14 N 7 31 15 P 75 As 33 1 Sb 51 09 Bi 83 16 O 8 3 S 16 79 Se 34 18 Te 5 3 10 Na Po 84 19 F 9 35.5 Cl 17 80 Br 35 17 I 53 3 10 Na At 85 4 He 0 Ne 10 40 Ar 18 84 Kr 36 131 Xe 54 Rn 86 Marks Grid [ For Examiner s use only ] Question Number Maximum Mark Actual Mark Section A Section B 1 3 4 5 6 7 8 9 10 10 10 10 10 10 0 0 0 Theory Total Theory Paper: 85% Practical: 15% Final Score: 100% Chemistry :: HY 015 :: Year 9 :: Track 3 Page 1 of 6
Section A: This section carries 60 marks. Answer all questions in this section. 1a. Label each process as a physical or chemical change: i) perfume evaporating on your skin ii) a bomb exploding iii) wood rotting iv) a piece of iron rusting v) melting copper metal 5 b. Name the following equipment: i) ii) iii) iv) v) 5 a. Write the chemical formula of the following substances: i) potassium oxide ii) sodium nitride iii) magnesium nitrate iv) iron(iii) chloride v) lead(ii) sulfate 5 Chemistry :: HY 015 :: Year 9 :: Track 3 Page of 6
b. Write the chemical name of the following substances: i) KBr ii) NH 4Cl iii) FeCl iv) Al (SO 4) 3 v) Ca(NO ) 5 3 Convert the following word equations into balanced chemical equations: a. hydrogen + oxygen water b. sodium + chlorine sodium chloride c. aluminium + oxygen aluminium oxide d. sodium + water sodium hydroxide + hydrogen e. calcium hydroxide + carbon dioxide calcium carbonate + water 4a. Fill in the missing gaps in this table: Symbol Atomic no. Mass no. No. of protons No. of electrons C 1 6 No. of neutrons O - 8 16 Al 3+ 13 7 Ne 10 10 6 b. Write the electron configuration of the following: i) a sodium atom ii) a fluorine atom iii) a magnesium atom iv) a nitride ion 4 Chemistry :: HY 015 :: Year 9 :: Track 3 Page 3 of 6
5a Lithium fluoride (LiF) is an ionic substance. Draw a dot cross diagram to show the ions of this compound. 5 b. Ammonia (NH 3) is a covalent compound. Draw a dot cross diagram to show the bonding in this compound. 5 6 This question is about the kinetic theory of matter. Use your knowledge of this theory to explain the following statements: a. You can smell hot coffee from several metres away, yet you have to be near cold coffee to smell it. b. Scientists calculate that gas particles can travel at speeds of up to 500 m/s. However when a person wearing a perfume enters a room, it takes several minutes for the smell to reach the back of the room. Chemistry :: HY 015 :: Year 9 :: Track 3 Page 4 of 6
c. The following apparatus was set up. After some time a white ring of smoke was observed. Give explanations for the following observations: i) It took a few minutes before for the white cloud to form. ii) The white cloud formed nearer to the cotton wool soaked in the hydrochloric acid. iii) Warming the concentrated ammonia solution and hydrochloric acid before carrying out the experiment would reduce the time taken for the white cloud to form. Section B: This section carries 40 marks. Answer any two questions from this section on the foolscaps provided. 7 Iron filings, sand and ammonium chloride were found mixed together in a beaker. A student was given the task of separating the three substances from each other. a. With the aid of a diagram, describe what the student should do to separate the iron filings from the rest of the mixture. 5 b. The remaining mixture now contains sand and ammonium chloride. The student was told that ammonium chloride sublimes on heating. It decomposes into two gases, ammonia and hydrogen chloride. On cooling they reform ammonium chloride in the solid state. i) Is it true that ammonium chloride sublimes? 1 ii) What is the name given for what happens to ammonium chloride on heating? 1 Chemistry :: HY 015 :: Year 9 :: Track 3 Page 5 of 6
iii) With the aid of a labelled diagram, describe a method to separate sand and ammonium chloride using heat only. 5 c. Chromatography is another separating technique that chemists use. Ink is normally made of coloured liquids that are mixed together to obtain a particular shade of colour. i) Describe how this technique is performed. 3 ii) Draw a labelled diagram of a chromatography setup. 3 iii) Why do the different coloured inks separate from each other on the chromatogram? 8 A student was given a task to obtain salt (NaCl) from a sample of rock salt. a. What are the two main components of rock salt? 1 b. State which substance is soluble and which is insoluble in water. c. What is the name of liquids that dissolve solid substances? 1 d. What is the name of a substance that dissolves in a liquid? 1 e. What is the name of the mixture that results when a substance dissolves in a liquid? 1 f. With the aid of labelled diagrams, describe what the student should do to separate the rock and the salt from each other. It is important that the student should have both rock and salt available as separate solids. 1 g. It is normal for the salt in rock salt to be a mixture of salts. What should the student do to check whether the salt obtained is pure? 9 Oil, water and ethanol are three liquids. Water and ethanol mix well together but they do not mix with oil. a. What are liquids that mix together called? 1 b. What are liquids that do not mix together called? 1 c. With the aid of a labelled diagram describe what you would do to separate the oil from the rest of the liquids. 7 d. Oil stays on top of the mixture. Why do you think this happens? 1 e. Describe what you would do to separate the remaining water from ethanol. Draw a labelled diagram to illustrate your answer. 10 Chemistry :: HY 015 :: Year 9 :: Track 3 Page 6 of 6