Home › Free Resources › Chemistry Worksheets › GCSE / IGCSE Chemistry – Chemical Changes and Energy
Free Chemistry Worksheet

GCSE / IGCSE Chemistry – Chemical Changes and Energy

Reactivity series, acids and bases, electrolysis, energy changes.

WhatsApp Mr. AhmadBook a trial lesson (50% off)Free worksheets
12 questions  ·  37 marks  ·  answers included  ·  GCSE / IGCSE (Edexcel / Cambridge style)
Download the PDFAsk about a question

This worksheet covers:

  • This worksheet covers the reactivity series
  • Acids and bases
  • Electrolysis
  • Energy changes

Use the relative atomic masses given in each question (rounded to whole numbers, as used at GCSE/IGCSE level); a calculator is allowed.

Questions

Section A – Reactivity and Acids/Bases

Skills
1

Place the following metals in order of reactivity, most reactive first: copper, magnesium, zinc, iron.

Show answer
Magnesium, zinc, iron, copper (most to least reactive).
[2]
2

Write the balanced symbol equation, including state symbols, for the reaction between magnesium and dilute hydrochloric acid.

Show answer
$\text{Mg}(s) + 2\text{HCl}(aq) \rightarrow \text{MgCl}_2(aq) + \text{H}_2(g)$
[3]
3

Define “neutralisation” and write the balanced symbol equation for the reaction between sodium hydroxide and sulfuric acid.

Show answer
Neutralisation is the reaction between an acid and a base in which they react to form a salt and water. $2\text{NaOH}(aq) + \text{H}_2\text{SO}_4(aq) \rightarrow \text{Na}_2\text{SO}_4(aq) + 2\text{H}_2\text{O}(l)$
[3]
4

Calculate the relative formula mass ($M_r$) of calcium carbonate, $\text{CaCO}_3$. ($A_r$: Ca $=40$, C $=12$, O $=16$)

Show answer
$M_r = 40 + 12 + (3\times16) = 40+12+48 = 100$.
[2]

Section B – Electrolysis and Energy Changes

Exam-style
5

Explain, using ionic half-equations, what happens at each electrode during the electrolysis of molten lead(II) bromide, $\text{PbBr}_2$.

Show answer
At the cathode (negative electrode), $\text{Pb}^{2+}$ ions are reduced (gain electrons) to form lead metal: $\text{Pb}^{2+} + 2e^{-} \rightarrow \text{Pb}$. At the anode (positive electrode), $\text{Br}^{-}$ ions are oxidised (lose electrons) to form bromine: $2\text{Br}^{-} \rightarrow \text{Br}_2 + 2e^{-}$.
[4]
6

Explain why aluminium is extracted by electrolysis rather than by reduction with carbon.

Show answer
Aluminium is more reactive than carbon, so carbon cannot remove the oxygen from (reduce) aluminium oxide. Electrolysis of molten aluminium oxide (dissolved in molten cryolite to lower its melting point) is used instead to separate the aluminium and oxygen.
[2]
7

In an experiment, $50\,\text{cm}^3$ of dilute hydrochloric acid at $20.0^{\circ}\text{C}$ was reacted with excess magnesium ribbon. The maximum temperature reached was $34.5^{\circ}\text{C}$. Calculate the temperature change, and state whether the reaction is exothermic or endothermic.

Show answer
$\Delta T = 34.5-20.0 = 14.5^{\circ}\text{C}$ (a rise). The reaction is exothermic, since the temperature increases as energy is released to the surroundings.
[2]
8

Using the temperature change in the previous question, calculate the energy change in joules, given the specific heat capacity of the solution is $4.2\,\text{J/g}^{\circ}\text{C}$ and the mass of solution is $50\,\text{g}$.

Show answer
$Q=mc\Delta T = 50\times4.2\times14.5 = 3045\,\text{J}$ (3.045 kJ).
[3]

Section C – Extended / Challenge

9

A student carries out an electrolysis experiment using a copper sulfate solution to electroplate a metal spoon with copper.(a) State which electrode, anode or cathode, the spoon should be, and explain why.(b) Write the half-equation for the reaction occurring at the copper anode used in electroplating.

Show answer
(a) The spoon should be the cathode (negative electrode), so that positively charged $\text{Cu}^{2+}$ ions in the solution are attracted to it and are reduced (gain electrons) to deposit as a layer of copper metal on its surface.(b) At the copper anode: $\text{Cu}(s) \rightarrow \text{Cu}^{2+}(aq) + 2e^{-}$ (the copper anode dissolves, releasing copper ions into solution).
[4]
10

Using bond energies, calculate the overall enthalpy change for the reaction $\text{H}_2 + \text{Cl}_2 \rightarrow 2\text{HCl}$, given: bond energy H–H $=+436\,\text{kJ/mol}$, Cl–Cl $=+243\,\text{kJ/mol}$, H–Cl $=+432\,\text{kJ/mol}$.

Show answer
Energy to break bonds $=436+243=679\,\text{kJ/mol}$. Energy released forming bonds $=2\times432=864\,\text{kJ/mol}$. $\Delta H = 679-864=-185\,\text{kJ/mol}$ (exothermic).
[4]
11

Calculate the percentage of aluminium by mass in aluminium oxide, $\text{Al}_2\text{O}_3$. ($A_r$: Al $=27$, O $=16$)

Show answer
$M_r(\text{Al}_2\text{O}_3)=(2\times27)+(3\times16)=54+48=102$. Percentage Al $=\dfrac{54}{102}\times100=52.9\%$ (3 s.f.).
[3]
12

A displacement reaction occurs when zinc granules are added to copper(II) sulfate solution.(a) Write the balanced symbol equation for this reaction.(b) Explain, in terms of electron transfer, why this is a redox reaction, identifying which species is oxidised and which is reduced.

Show answer
(a) $\text{Zn}(s) + \text{CuSO}_4(aq) \rightarrow \text{ZnSO}_4(aq) + \text{Cu}(s)$(b) Zinc atoms lose electrons to form $\text{Zn}^{2+}$ ions (oxidation), while $\text{Cu}^{2+}$ ions gain electrons to form copper atoms (reduction). Since oxidation and reduction both occur, this is a redox reaction.
[5]

Related worksheets

More worksheets in GCSE & IGCSE Chemistry:

GCSE / IGCSE Chemistry – Atomic Structure and the Periodic TableGCSE / IGCSE Chemistry – Bonding and StructureGCSE / IGCSE Chemistry – Quantitative ChemistryGCSE / IGCSE Chemistry – Rates, Equilibrium and OrganicGCSE / IGCSE Chemistry – Analysis and the Atmosphere

All chemistry worksheets  ·  Full resource library  ·  Chemistry tuition with Mr. Ahmad

Get new chemistry worksheets by email

One short email when new worksheets are added. No spam, unsubscribe any time.



    Book a trial lesson (50% off)

    Try a full first lesson with Mr. Ahmad at 50% off before you commit to anything. It is a real lesson, not a sales call: bring a topic the student is stuck on and we will work through it together.

    • Online from anywhere in the world, or in person across Dubai
    • You get honest feedback on where the student stands and what to fix first
    • No contract — if it is not the right fit, that is fine

    Prefer to talk? Message on WhatsApp and you will hear back within 24 hours.



      Stuck on this topic?

      Book a trial lesson with Mr. Ahmad at 50% off and bring this worksheet with you — online worldwide or in person in Dubai.

      WhatsApp nowBook a trial lesson (50% off)
      Scroll to Top