OCR GCSE (9-1) Gateway Science Chemistry a Learner Resource -Chemical Reactions

Learner resource

Topic C3: Chemical reactions Instructions and answers for teachers

These instructions cover the learner resource activity which can be found on page 8 These activities support OCR GCSE (9-1) Gateway Science Chemistry A.

When distributing the activity section to the learners either as a printed copy or as a Word file you will need to remove the teacher instructions section.

Answers are shown in grey.

Activity 1 – Change during a reaction Answer the questions below.

1. There are many ways to know that a reaction is progressing.

One way is if you see fizzing. While a reaction is fizzing, you know that a chemical change is happening.

List three other ways that show a reaction is progressing.

Change in temperature

Change in colour

Something new created

a) The beaker and its contents have changed in mass during 5 minutes of reacting.

Can you explain why?

Gas is made by the reaction

Gas is given off into the environment

b) Calculate the change in mass caused by the reaction during the 5 minutes.

9.46 - 8.94 = 0.52 g

c) Other than fizzing, how else can you tell that the reaction has finished?

The limestone will disappear/fully dissolve

H2O H2SO4 NaOH K2Cr2O7 NaHCO3

2 3 3 3 4

2. How many atoms in total are in the following compounds?

AgBr BaF2 CH4 FO2 Ga2O3 H2CO3 2 3 5 3 5 6

3. How many of each element are in each of the following compounds?

Foundation tier:

KCN LiOH MgCO3 NH4Br O2F2 POCl3 Sb2OS2

1:1:1 1:1:1 1:1:3 1:4:1 2:2 1:1:3 2:1:2

Both tiers:

Mg(OH)2 W(CO)6 Al2BeO4 Ba(SCN)2 CH2(OH)2 Cd(N3)2

1:2:2 1:6:6 2:1:4 1:2:2 1:4:2 1:6

Higher tier:

(CH3)3CCl Cr2(SO4)3 (NH2)2CO Pb(NO3)2 Sr(MnO4)2 Ti(CHO2)2

4:9:1 2:3:1 2:4:1:1 1:2:6 1:2:8 1:2:2:4

4. Extension task

Which substance, clay or talc, has the most atoms?

How many atoms are there in each substance?

Clay MgNaAl5(Si4O10)3(OH)6 or Talc Mg3(Si4O10)(OH)2

61 atoms 21 atoms Activity 3 – Ionic compounds

Use the ionic formulae card to construct formulae for the ionic compounds, as shown in the example given for sodium carbonate, and fill in the table.

Some of the compounds are marked with an asterisk (*). This shows that the ionic formulae for these compounds may need you to use brackets. For example, if you needed two hydroxide ions (OH-) to balance one calcium ion (Ca2+), you would write the formula of the

compound as Ca(OH)2.

The compounds marked with two asterisks (**) shows that the construction of the ionic formulae for these compounds are even more difficult to determine.

Ionic compound Formula Ionic compound Formula

sodium carbonate Na2CO3 zinc nitrate Zn(NO3)2

silver nitrate AgNO3 potassium sulfate K2SO4

calcium bromide CaBr2 magnesium sulfide MgS

aluminium copper hydroxide* Cu(OH) Al(OH) 2 hydroxide* 3

ammonium iron(II) nitrate* Fe(NO3)2 NH4Cl chloride

sodium hydrogen iron(III) iodide FeI NaHCO 3 carbonate 3

iron(III) lead sulfate PbSO Fe (CO ) 4 carbonate** 2 3 3

zinc sulfide ZnS barium carbonate BaCO3

ammonium (NH4)2SO4 lithium sulfate* Li2SO4 sulfate ** #

Ionic Formulae Card

Name Formula Name Formula

Hydrogen H+ Chloride Cl -

Sodium Na+ Bromide Br -

SilverS Ag+ Fluoride F-

Potassium K+ Iodide I-

Lithium Li+ Hydroxide OH-

+ - Ammonium NH4 Nitrate NO3

Barium Ba2+ Oxide O2-

Calcium Ca2+ Sulfide S2-

2+ 2- Copper (II) Cu Sulfate SO4

2+ 2- Magnesium Mg Carbonate CO3

2+ - Zinc Zn Hydrogen carbonate HCO3

Lead Pb2+

Iron (II) Fe2+

Iron (III) Fe3+

Aluminium Al3+

2) The last two equations will need balancing once you have finished.

oxidised

Al2O3 + 3Mg  3MgO +2Al Oxidised…………Mg ……….. / Reduced…………AAll………..

reduced

oxidised

2H2 + O2  2H2O Oxidised…………H………… / Reduced…………OO…………

reduced

oxidised

CH4 + 2O2  CO2 + 2H2O Oxidised…………CC…..……… / Reduced…………OO………..

reduced

oxidised

CO2 + Ca  CaO + CO Oxidised…………CaCa……….. / Reduced………CC…………….

oxidised

4 FeO + O2  2Fe2O3 Oxidised…………Fe……….. / Reduced…………O………….

reduced

oxidised

2Fe2O3 + 3 C  4 Fe + 3CO2 Oxidised…………CC……… / Reduced…………FeFe………

reduced

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Topic C3: Chemical reactions

Activity 1 – Change during a reaction Answer the questions below.

1. There are many ways to know that a reaction is progressing.

One way is if you see fizzing. While a reaction is fizzing, you know that a chemical change is happening.

List three other ways that show a reaction is progressing.

2. In the reaction below, a piece of limestone is reacting with an acid in a beaker on top of a weighing scale.

a) The beaker and its contents have changed in mass during 5 minutes of reacting. Can you explain why?

b) Calculate the change in mass caused by the reaction during the 5 minutes.

H2O H2SO4 NaOH K2Cr2O7 NaHCO3

2. How many atoms in total are in the following compounds?

AgBr BaF2 CH4 FO2 Ga2O3 H2CO3

3. How many of each element are in each of the following compounds?

Foundation tier:

KCN LiOH MgCO3 NH4Br O2F2 POCl3 Sb2OS2

Both tiers:

Mg(OH)2 W(CO)6 Al2BeO4 Ba(SCN)2 CH2(OH)2 Cd(N3)2

Higher tier:

(CH3)3CCl Cr2(SO4)3 (NH2)2CO Pb(NO3)2 Sr(MnO4)2 Ti(CHO2)2

4. Extension task

Which substance, clay or talc, has the most atoms?

How many atoms are there in each substance?

Activity 3 – Ionic compounds

Use the ionic formulae card to construct formulae for the ionic compounds, as shown in the example given for sodium carbonate, and fill in the table.

Some of the compounds are marked with an asterisk (*). This shows that the ionic formulae for these compounds may need you to use brackets. For example, if you needed two hydroxide ions (OH-) to balance one calcium ion (Ca2+), you would write the formula of the compound as Ca(OH)2.

The compounds marked with two asterisks (**) shows that the construction of the ionic formulae for these compounds are even more difficult to determine.

Ionic compound Formula Ionic compound Formula

sodium carbonate Na2CO3 zinc nitrate

silver nitrate potassium sulfate

calcium bromide magnesium sulfide

aluminium copper hydroxide* hydroxide*

ammonium iron(II) nitrate* chloride

sodium hydrogen iron(III) iodide carbonate

iron(III) lead sulfate carbonate**

zinc sulfide barium carbonate

ammonium lithium sulfate* sulfate **

Name Formula Name Formula

Hydrogen H+ Chloride Cl -

Sodium Na+ Bromide Br -

SilverS Ag+ Fluoride F-

Potassium K+ Iodide I-

Lithium Li+ Hydroxide OH-

+ - Ammonium NH4 Nitrate NO3

Barium Ba2+ Oxide O2-

Calcium Ca2+ Sulfide S2-

2+ 2- Copper (II) Cu Sulfate SO4

2+ 2- Magnesium Mg Carbonate CO3

2+ - Zinc Zn Hydrogen carbonate HCO3

Lead Pb2+

Iron (II) Fe2+

Iron (III) Fe3+

Aluminium Al3+

2) The last two equations will need balancing once you have finished.

Al2O3 + 3Mg  3MgO +2Al Oxidised………… ……….. / Reduced…………Al………..

2H2 + O2  2H2O Oxidised…………H ………… / Reduced…………O …………

CH4 + 2O2  CO2 + 2H2O Oxidised…………C …..……… / Reduced…………O ………..

CO2 + Ca  CaO + CO Oxidised…………Ca ……….. / Reduced………C …………….

FeO + O2  2Fe2O3 Oxidised…………Fe ……….. / Reduced…………O ………….