Grade 11 Physical Sciences · Chemical Change · Paper 2 (Chemistry)

Energy and Chemical Change Grade 11

Real Energy and Chemical Change past paper questions and answers from 2022 to 2025, with each memo split into the ticks examiners give. Try one, mark yourself, and see exactly which skill cost you marks.

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Question 1.5 · November 2025 · Paper 2 · Provincial · 2 marks

Various options are provided as possible answers to the following questions. Choose the answer and write only the letter (A–D) next to the question numbers (1.1 to 1.10) in the ANSWER BOOK, for example 1.11 E.

1.5 Consider the following statement regarding the activated complex during a chemical reaction:

(I) The activation energy must be overcome to reach the activated complex.
(II) It is the unstable transition state from reactants to products.
(III) It is the energy released or absorbed during a chemical reaction.

Which of the above statement(s) is/are CORRECT about the activated complex?(2)

A II and III only
B II only
C I and II only
D I only

Work it out on paper first. Then mark yourself with the official memo, one tick at a time.

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More Energy and Chemical Change Grade 11 questions and answers

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4. Question 1.9 · November 2024 · Paper 2 · Provincial · 2 marks
1.9 Which ONE of the following statements is TRUE for an EXOTHERMIC reaction?(2)
1. A More energy is released than absorbed.
2. B More energy is absorbed than released.
3. C Heat of reaction ( $Δ H$ ) is positive.
4. D Energy of the products is greater than the energy of the reactants.
Show the memo (1 tick)Memo
1. ✓
  Correct optionIn an exothermic reaction more energy is released when new bonds form than is absorbed to break the old bonds. So $Δ H < 0$ and the products have LESS energy than the reactants.
  
  Answer: A
  2 marks · Interpret the energy change of reactions
5. Question 5.1 · November 2024 · Paper 2 · Provincial · 2 marks
One of the steps in the preparation of sulphuric acid in the industry is represented by the following reaction:

$2 SO_{2} (g) + O_{2} (g) \to 2 SO_{3} (g)$

The graph below shows the energy change during this reaction.
5.1 Write down the type of reaction represented by above graph. Choose from EXOTHERMIC or ENDOTHERMIC. Explain your answer.(2)
Show the memo (2 ticks)Memo
1. ✓
  Type of reactionEXOTHERMIC
  1 mark · Interpret the energy change of reactions
2. ✓
  ReasonEnergy is released
  OR $Δ H < 0$
  OR more energy is released than absorbed.
  1 mark · Interpret the energy change of reactions
6. Question 1.9 · November 2023 · Paper 2 · Provincial · 2 marks
1.9 Instant hot and cold packs function by dissolving a salt into water. As the salt dissociates, heat is either released in an exothermic reaction or absorbed in an endothermic reaction. Which of the following reactions will be best suited to be used as a hot pack?(2)
1. A $CH_{3} COOMg + 4 H_{2} O \to CH_{3} COOMg.4H_{2} O$ $Δ H = - 13, 3$ kJ·mol $^{- 1}$
2. B $CH_{3} COONa + 3 H_{2} O \to CH_{3} COONa.3H_{2} O$ $Δ H = - 19, 7$ kJ·mol $^{- 1}$
3. C $Ba(OH)_{2} + H_{2} O \to Ba^{2 +} + 2 OH^{-} + H_{2} O$ $Δ H = + 21, 9$ kJ·mol $^{- 1}$
4. D $NH_{4} NO_{3} + H_{2} O \to NH_{4}^{+} + NO_{3}^{-} + H_{2} O$ $Δ H = + 25, 4$ kJ·mol $^{- 1}$
Show the memo (1 tick)Memo
1. ✓
  Correct optionA hot pack must RELEASE heat, so the reaction must be exothermic ( $Δ H < 0$ ). Only A and B are exothermic. B releases more energy per mole ( $- 19, 7$ kJ·mol $^{- 1}$ against $- 13, 3$ kJ·mol $^{- 1}$ ), so it is best suited.
  
  Answer: B
  2 marks · Interpret the energy change of reactions
7. Question 1.1 · November 2023 · Paper 2 · Provincial · 2 marks
1.1 Consider the definition given below:

The high energy transition state between products and reactants.

This is the definition of ...(2)
1. A a catalyst.
2. B heat of reaction.
3. C activation energy.
4. D activated complex.
Show the memo (1 tick)Memo
1. ✓
  Correct optionThe activated complex is the unstable, high-energy arrangement of atoms at the top of the energy hump, between reactants and products. Activation energy is the ENERGY needed to reach that state, not the state itself.
  
  Answer: D
  2 marks · Define rate and energy terms
8. Question 5.1.2 · November 2023 · Paper 2 · Provincial · 2 marks
5.1 1,56 g of calcium carbonate is heated as shown in diagram below.

The calcium carbonate decomposes according to the balanced equation:

$CaCO_{3} (s) \to CaO(s) + CO_{2} (g)$ $Δ H > 0$

0,163 g of $CO_{2}$ is produced during this decomposition.
5.1.2 Give a reason for your answer in QUESTION 5.1.1.(2)
Show the memo (1 tick)Memo
1. ✓
  Reason $Δ H > 0$ / Net energy is absorbed / Energy of products greater than that of reactants.
  2 marks · Interpret the energy change of reactions
9. Question 8.2 · November 2023 · Paper 2 · Provincial · 2 marks
Certain chemical reactions are often used to reduce swelling after an athletic injury. In a lab experiment the following reaction was tested and the sketch graph below was obtained.

$NH_{4} C ℓ + H_{2} O \to NH_{4}^{+} + C ℓ^{-} + H_{2} O$
8.2 Explain the answer to QUESTION 8.1.(2)
Show the memo (1 tick)Memo
1. ✓
  ReasonThe products have more potential energy than the reactants.
  OR
  More energy is absorbed than released.
  2 marks · Interpret the energy change of reactions
10. Question 1.3 · November 2022 · Paper 2 · Provincial · 2 marks
1.3 The minimum amount of energy needed for a chemical reaction to start is called …(2)
1. A activation energy.
2. B catalyst.
3. C heat of reaction.
4. D bond energy.
Show the memo (1 tick)Memo
1. ✓
  Correct optionActivation energy is the minimum energy needed for a reaction to take place. A catalyst only lowers it; the heat of reaction is the net energy change; bond energy is the energy to break one mole of a bond.
  
  Answer: A
  2 marks · Define rate and energy terms

Energy and Chemical Change Grade 11 videos

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Energy and Chemical Change grade 11: Activation energy, heat of reaction, catalyst and MORE!Miss Martins Maths and Science

Energy and chemical change Heat Of Reaction Grade 11 & 12 ChemistryMiss Martins Maths and Science

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