CIE iGCSE Co-Ordinated Science C2.1 Elements, compounds and mixtures Exam Style Questions Paper 3
Question
(a) The list gives the names of seven elements.
calcium
carbon
copper
oxygen
nitrogen
potassium
sulfur
Answer the questions about these elements.
Each element may be used once, more than once or not at all.
State which element:
(i) is in Group I of the Periodic Table.
…………………………………………………………………………………………………………………….
(ii) is in diamond.
…………………………………………………………………………………………………………………….
(iii) is 78% of clean air.
…………………………………………………………………………………………………………………….
(iv) gives a lilac flame test.
…………………………………………………………………………………………………………………….
(v) is used in electroplating.
…………………………………………………………………………………………………………………….
(vi) is used in the manufacture of sulfuric acid.
…………………………………………………………………………………………………………………….
(b) Atoms contain protons, neutrons and electrons.
State which of these particles:
are in shells around the nucleus ………………………………….
have a positive charge ………………………………….
have the smallest mass. ………………………………….
▶️Answer/Explanation
Ans: 2(a)(i) potassium ;
2(a)(ii) carbon ;
2(a)(iii) nitrogen ;
2(a)(iv) potassium ;
2(a)(v) copper ;
2(a)(vi) sulfur ;
2(b) electrons ;
protons ;
electron ;
Question
(a) (i) There are different methods of separating mixtures.
Fig. 2.1 shows that distillation is used to separate water from aqueous potassium chloride.
Complete Fig. 2.1 to show how the other three substances are separated from the mixtures.
(ii) Name the solvent in aqueous copper sulfate.
…………………………………………………………………………………………………………………….
(iii) State one use for bitumen.
…………………………………………………………………………………………………………………….
(b) The treatment of a water supply uses filtration and chlorination.
Give a reason for using filtration and chlorination.
filtration ………………………………………………………………………………………………………
……………………………………………………………………………………………………………………
chlorination …………………………………………………………………………………………………
……………………………………………………………………………………………………………………
(c) Electrolysis is a process which uses electricity to break down a compound.
For example, when molten lead bromide is electrolysed, lead and bromine are made.
Complete the sentences about the electrolysis of lead bromide using words from the list.
Each word may be used once, more than once or not at all.
bromine cell electrolyte electrons hydrogen
ions lead molecules negative positive
Molten lead bromide is called the …………………………………………….. because it contains
…………………………………………….. which are free to move.
The …………………………………………….. electrode is called the cathode
and the …………………………………………….. electrode is called the anode.
…………………………………………….. forms at the anode and …………………………………………
forms at the cathode.
▶️Answer/Explanation
Ans: 2(a)(i)
one pair of links correct ;
two pairs of links correct ;
three pairs of links correct ;
2(a)(ii) water ;
2(a)(iii) road surfaces ;
2(b) filtration – removes solid particles ;
chlorination – kills microbes / sterilises water ;
2(c) electrolyte ;
ions ;
negative and positive (in that order) ;
bromine and lead (in that order) ;
Question
(a) Substances are separated from mixtures of substances using different methods.
Draw one straight line from each substance to the correct method of separating it from the mixture.
One line has been drawn for you.
(b) One reason for separating mixtures is to purify substances.
Explain the importance of purity in the manufacture of substances used in food additives.
(c) The element lead is obtained from the compound lead(II) bromide by electrolysis.
(i) Describe the difference between an element and a compound.
(ii) Complete the sentences to describe the electrolysis of lead(II) bromide.
Electrolysis is the breakdown of molten lead(II) bromide by the passage of ………………………………………… .
The gas released at the positive electrode is ………………………………………… and ………………………………………… is formed at the negative electrode.
The negative electrode is called the ………………………………………… .
(d) A student reacts dilute hydrochloric acid with four metals.
The student’s observations are shown in Table 5.1.
Place the four metals in order of their reactivity from the most reactive to the least reactive.
▶️Answer/Explanation
Ans : 5(a) 
5(b) to avoid poisoning ;
5(c)(i) element contains only one type of atom /
compound consists of (atoms of) two or more elements (chemically combined) ;
5(c)(ii) electricity ;
bromine and lead ;
cathode ;
5(d) calcium
magnesium
lead
copper
;;
Question
(a) The list gives the names of six compounds.
aluminium oxide
ammonium nitrate
carbon dioxide
lead bromide
sodium chloride
sulfur dioxide
Answer the questions about these compounds.
Each compound may be used once, more than once or not at all.
State which compound:
(i) has the formula PbBr2.
(ii) is a salt from which ammonia can be displaced.
(iii) is an acidic oxide.
(iv) is a greenhouse gas.
(v) is the main constituent of bauxite.
(b) Aluminium, copper and iron are all solid metals.
State three general physical properties of solid metals.
1 …………………………………………………………………………
2 …………………………………………………………………………
3 …………………………………………………………………………
(c) (i) Duralumin is an alloy of aluminium.
Table 2.1 shows the percentage composition of duralumin.
Calculate the mass of aluminium in 20 kg of duralumin.
mass of aluminium = ……………………………………………. kg
(ii) Table 2.2 shows the melting points of aluminium, copper, magnesium and duralumin.
Duralumin does not have a precise melting point but melts over a range of temperatures.
Explain why duralumin does not have a precise melting point.
▶️Answer/Explanation
Ans : 2(a)(i) lead bromide ;
2(a)(ii) ammonium nitrate ;
2(a)(iii) carbon dioxide / sulfur dioxide ;
2(a)(iv) carbon dioxide ;
2(a)(v) aluminium oxide ;
2(b) any three from:
conducts heat ;
conducts electricity ;
malleable ;
high melting/boiling point ;
2(c)(i) 95 / 100 × 20 = 19 (kg) ;
2(c)(ii) because it is not a pure substance / it is a mixture ;
Question
(a) (i) An atom of calcium has 20 protons and 20 neutrons.
State the number of electrons in this calcium atom.
(ii) State the number of electrons in one calcium ion, Ca2+.
(b) Limestone (calcium carbonate) and lime (calcium oxide) are both calcium compounds.
Fig. 11.1 shows a limekiln in which calcium carbonate thermally decomposes to make calcium oxide and carbon dioxide.
(i) Write the word equation for the thermal decomposition of calcium carbonate.
(ii) The mass of calcium oxide made in this reaction is always less than the mass of calcium carbonate used.
Suggest why.
(iii) The decomposition of calcium carbonate to calcium oxide is an endothermic reaction.
State the meaning of the term endothermic.
(iv) One use for limestone is in the production of lime.
State one other use of limestone.
(v) Suggest why the calcium carbonate is broken into small pieces before being thermally decomposed.
(c) Calcium carbonate has the formula CaCO3.
(i) State the number of different elements shown in this formula.
(ii) State the total number of atoms shown in this formula.
▶️Answer/Explanation
Ans : 11(a)(i) 20 (electrons) ;
11(a)(ii) 18 (electrons) ;
11(b)(i) calcium carbonate → calcium oxide + carbon dioxide ;
11(b)(ii) carbon dioxide released ;
11(b)(iii) (thermal) energy taken in ;
11(b)(iv) neutralising acidified soil ;
11(b)(v) to increase surface area ;
so that reaction is faster ;
11(c)(i) three ;
11(c)(ii) five ;
Question
(a) Five words are shown in the boxes on the left. Five descriptions are shown in the boxes on the right.
Draw one straight line from each word to its correct description.
(b) A student investigates the reaction between calcium carbonate and dilute hydrochloric acid.
Fig. 2.1 shows the apparatus the student uses.
A salt solution and carbon dioxide are made. The carbon dioxide gas is collected in apparatus A.
(i) State the name of apparatus A shown in Fig. 2.1.
…………………………………………………………………………………………………………………….
(ii) State the name of the salt made.
…………………………………………………………………………………………………………………….
(iii) State the chemical test for carbon dioxide. Include the observation for a positive result.
test ……………………………………………………………………………………………………………………
observation …………………………………………………………………………………………………………
(iv) It takes 50 seconds to collect 90cm$^{3}$ of carbon dioxide gas.
Calculate the rate at which carbon dioxide is made in cm$^{3}$/s.
rate = ………………………………………. cm$^{3}$/ s
(v) State two changes to the reaction conditions that reduce the rate of reaction.
1 ……………………………………………………………………………………………………………………….
2 ……………………………………………………………………………………………………………………….
(vi) Calcium carbonate has the formula CaCO$_{3}$.
State the number of different elements present in calcium carbonate.
…………………………………………………………………………………………………………………….
▶️Answer/Explanation
Ans: 2(a)
1 correct 1 mark ;
2 correct 2 marks ;
3 or 4 correct 3 marks ;
5 correct 4 marks ;
2(b)(i) measuring cylinder ;
2(b)(ii) calcium chloride ;
2(b)(iii) (bubble the gas through) lime water ;
goes milky / cloudy ;
2(b)(iv) 1.8 (cm$^{3}$/ s) ;
2(b)(v) any two from:
lower temperature (of acid) ;
lower concentration of acid ;
decrease surface area ;
2(b)(vi) 3 ;
Question
(a) Sodium and chlorine are elements.
Sodium chloride is a compound.
Describe what is meant by an element and a compound.
element …………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………………………
compound …………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
(b) Sodium reacts with chlorine to make sodium chloride.
Balance the symbol equation for this reaction.
………Na + Cl$_{2}$ ………NaCl
(c) When sodium reacts with chlorine, sodium atoms become sodium ions and chlorine atoms become chloride ions.
The electron configuration of a sodium atom is 2.8.1.
The electron configuration of a chlorine atom is 2.8.7.
State the electron configuration of a sodium ion and a chloride ion.
sodium ion ………………………………………..
chloride ion ………………………………………..
(d) Describe the difference in the solubility in water of an ionic compound compared with a covalent compound.
…………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
(e) Sodium chloride contains chloride ions.
Describe the test for chloride ions and state the observation for a positive result.
test …………………………………………………………………………………………………………………………..
observation ……………………………………………………………………………………………………………….
(f) Fig. 11.1 shows the electrolysis of concentrated aqueous sodium chloride.
Complete the sentences about the electrolysis of concentrated aqueous sodium chloride.
Electrolysis is defined as the breakdown of an ionic compound when
………………………………. or in aqueous solution by the passage of ……………………………….
The gas released at the negative electrode is ………………………………. and the gas
released at the positive electrode is ………………………………. .
▶️Answer/Explanation
Ans: 11(a) element – contains only one type of atom ;
compound – contains two or more elements (chemically combined) ;
11(b) 2Na + Cl$_{2}$ → 2NaCl ;
11(c) sodium ion 2.8 ;
chloride ion 2.8.8 ;
11(d) solubility of ionic compound is greater ;
11(e) add acidified aqueous silver nitrate ;
white precipitate ;
11(f) molten ;
electricity ;
hydrogen ;
chlorine ;