Exothermic and endothermic reactions — Paper 1 · IGCSE Chemistry (9-1) 0971

11 Burning fuels is an exothermic reaction. What is meant by the term exothermic? A A gas is produced. B Energy is released. C Heat is absorbed. D The mass of the fuel decreases.

1 marks

Answer: B

This question in 0971/11 May/June 2018

13 Water is added to anhydrous copper(II) sulfate. What happens during the reaction? A The copper(II) sulfate turns blue and the solution formed gets colder. B The copper(II) sulfate turns blue and the solution formed gets hotter. C The copper(II) sulfate turns white and the solution formed gets colder. D The copper(II) sulfate turns white and the solution formed gets hotter.

1 marks

Answer: B

This question in 0971/11 May/June 2018

11 Dissolving ammonium chloride in water is an endothermic change. Which row shows the energy change and temperature change of the mixture during the dissolving of ammonium chloride? energy change temperature change A energy is absorbed decrease B energy is absorbed increase C energy is released decrease D energy is released increase

1 marks

Answer: A

This question in 0971/11 May/June 2019

11 The temperature of the water in two beakers, X and Y, is measured as 21.5 °C. 5 g of sodium chloride is dissolved in the water in beaker X. The temperature changes to 18.0 °C. 5 g of calcium oxide is dissolved in the water in beaker Y. The temperature changes to 29.4 °C. Which types of process are occurring in beakers X and Y? X Y A endothermic endothermic B endothermic exothermic C exothermic endothermic D exothermic exothermic

1 marks

Answer: B

This question in 0971/12 Oct/Nov 2019

11 The energy level diagram shows the energy of the reactants and products in a chemical reaction. reactants energy products progress of reaction Which row correctly describes the energy change and the type of reaction shown? description of type of reaction energy change A energy is given out endothermic to the surroundings B energy is given out exothermic to the surroundings C energy is taken in from endothermic the surroundings D energy is taken in from exothermic the surroundings

1 marks

Answer: B

This question in 0971/11 May/June 2020

11 The energy level diagram shows the energy of the reactants and products in a chemical reaction. reactants energy products progress of reaction Which row correctly describes the energy change and the type of reaction shown? description of type of reaction energy change A energy is given out endothermic to the surroundings B energy is given out exothermic to the surroundings C energy is taken in from endothermic the surroundings D energy is taken in from exothermic the surroundings

1 marks

Answer: B

This question in 0971/12 May/June 2020

14 Which energy level diagram represents an endothermic reaction? A B reactants products energy energy products reactants progress of reaction progress of reaction C D reactants reactants products energy energy products progress of reaction progress of reaction

1 marks

Answer: B

This question in 0971/12 Oct/Nov 2020

20 When pink crystals of cobalt(II) chloride are heated, steam is given off and the colour of the solid changes to blue. CoCl 2•6H2O CoCl 2 + 6H2O What happens when water is added to the blue solid? colour temperature A changes to pink decreases B changes to pink increases C remains blue decreases D remains blue increases

1 marks

Answer: B

This question in 0971/12 Oct/Nov 2020

12 The complete combustion of propane is exothermic. The equation for this reaction is shown. C3H8 + 5O2  3CO2 + 4H2O Which energy level diagram represents the complete combustion of propane? A B C3H8 + 5O2 3CO2 + 4H2O energy energy 3CO2 + 4H2O C3H8 + 5O2 progress of reaction progress of reaction C D 3CO2 + 4H2O C3H8 + 5O2 energy energy C3H8 + 5O2 3CO2 + 4H2O progress of reaction progress of reaction

1 marks

Answer: D

This question in 0971/11 May/June 2021

13 Which changes occur when hydrogen is burned in oxygen? energy change product A endothermic H2O only B endothermic H2O and CO2 C exothermic H2O only D exothermic H2O and CO2

1 marks

Answer: C

This question in 0971/11 May/June 2021

11 An energy level diagram for the reaction between substance X and substance Y to form substance Z is shown. Z energy X + Y progress of reaction Which statement is correct? A Energy is released as substance Z is formed. B Substance Z has more energy than substance X and substance Y. C The reaction is exothermic. D When substance X and substance Y react, the temperature increases.

1 marks

Answer: B

This question in 0971/12 Oct/Nov 2021

12 Which reactions are exothermic? 1 C + O2  CO2 2 CH4 + 2O2  CO2 + 2H2O 3 2H2 + O2  2H2O A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

1 marks

Answer: A

This question in 0971/12 Oct/Nov 2021

13 The equation for the reaction when hydrogen is used as a fuel is shown. 2H2 + O2  2H2O Which statement about this reaction is correct? A Energy is given out so the temperature of the surroundings decreases. B Energy is taken in so the temperature of the surroundings increases. C The reaction is endothermic so the temperature of the surroundings decreases. D The reaction is exothermic so the temperature of the surroundings increases.

1 marks

Answer: D

This question in 0971/11 May/June 2022

15 Water is added to anhydrous copper(II) sulfate. What happens during the reaction? A The copper(II) sulfate turns blue and the solution formed gets colder. B The copper(II) sulfate turns blue and the solution formed gets hotter. C The copper(II) sulfate turns white and the solution formed gets colder. D The copper(II) sulfate turns white and the solution formed gets hotter.

1 marks

Answer: B

This question in 0971/11 May/June 2022

11 Which type of reaction occurs when calcium carbonate is heated at a high temperature to produce calcium oxide and carbon dioxide? A combustion B endothermic C oxidation D reduction

1 marks

Answer: B

This question in 0971/12 May/June 2022

15 Water is added to anhydrous copper(II) sulfate. What happens during the reaction? A The copper(II) sulfate turns blue and the solution formed gets colder. B The copper(II) sulfate turns blue and the solution formed gets hotter. C The copper(II) sulfate turns white and the solution formed gets colder. D The copper(II) sulfate turns white and the solution formed gets hotter.

1 marks

Answer: B

This question in 0971/12 May/June 2022

26 Iron is extracted from hematite in the blast furnace at a temperature of about 1550 C. Which equation shows the main reaction that increases the temperature in the furnace? A CaCO3  CaO + CO2 B C + O2  CO2 C CO2 + C  2CO D Fe2O3 + 3CO  2Fe + 3CO2

1 marks

Answer: B

This question in 0971/12 May/June 2022

11 When an acid is added to an alkali, the temperature of the reaction mixture rises. Which words describe this reaction? A decomposition and endothermic B decomposition and exothermic C neutralisation and endothermic D neutralisation and exothermic

1 marks

Answer: D

This question in 0971/12 Oct/Nov 2022

11 A reaction pathway diagram is shown. products energy reactants progress of reaction Which statement about this reaction is correct? A The reaction rate increases during the reaction. B The reaction is endothermic. C The reaction transfers thermal energy to the surroundings. D The temperature of the surroundings increases.

1 marks

Answer: B

This question in 0971/11 May/June 2023

11 5 g of four different fuels are set alight and placed under a beaker containing 50 cm3 of water. The temperature of the water is taken at the start and after five minutes. Which fuel releases the most energy? temperature temperature at start after five minutes / °C / °C A 15 23 B 21 31 C 28 47 D 30 48

1 marks

Answer: C

This question in 0971/12 May/June 2023

28 Which reaction in the blast furnace releases heat energy? A C + O2 → CO2 B CaCO3 → CaO + CO2 C CO2 + C → 2CO D Fe2O3 + 3CO → 2Fe + 3CO2

1 marks

Answer: A

This question in 0971/12 May/June 2023

13 The initial and final temperatures of four different reactions are measured. Which reaction is the least exothermic? initial final temperature temperature / °C / °C A 19 25 B 21 18 C 22 17 D 22 26

1 marks

Answer: D

This question in 0971/12 Oct/Nov 2023

12 Which row describes what happens during an endothermic reaction? thermal energy is change in temperature of transferred the reaction mixture A from the surroundings decrease B from the surroundings increase C to the surroundings decrease D to the surroundings increase

1 marks

Answer: A

This question in 0971/11 May/June 2024

16 Water is added to anhydrous copper(II) sulfate. Which row describes the direction of energy change and the colour change of the mixture during the reaction? direction of energy change colour change A absorbed from the surroundings blue to white B absorbed from the surroundings white to blue C released to the surroundings blue to white D released to the surroundings white to blue

1 marks

Answer: D

This question in 0971/11 May/June 2024

15 Three reactions are described. 1 An acid is added to substance H. Rapid fizzing happens and the temperature decreases. 2 When substance J is ignited, it produces large quantities of heat. 3 Substance K reacts slowly with air and becomes warmer. Which reactions are endothermic? A 1, 2 and 3 B 1 and 2 only C 1 only D 2 and 3 only

1 marks

Answer: C

This question in 0971/12 May/June 2024

14 The temperature of the water in two beakers, X and Y, is measured as 21.5 C. 5 g of sodium chloride is dissolved in the water in beaker X. The temperature changes to 18.0 C. 5 g of calcium oxide is dissolved in the water in beaker Y. The temperature changes to 29.4 C. Which types of process are occurring in beakers X and Y? X Y A endothermic endothermic B endothermic exothermic C exothermic endothermic D exothermic exothermic

1 marks

Answer: B

This question in 0971/12 Oct/Nov 2024

13 Three statements about energy changes in chemical reactions are listed. 1 In an endothermic reaction, the temperature of the surroundings increases. 2 In an exothermic reaction, thermal energy is taken in from the surroundings. 3 In the reaction pathway diagram for an exothermic reaction, the energy level of the products is lower than the energy level of the reactants. Which statements are correct? A 1 and 2 B 1 only C 2 and 3 D 3 only

1 marks

Answer: D

This question in 0971/11 May/June 2025

14 Which reaction pathway diagram shows the largest increase in the temperature of the surroundings? (The scale on the y-axis is the same in each diagram.) A B products products energy energy reactants reactants progress of reaction progress of reaction C D reactants reactants products energy energy products progress of reaction progress of reaction

1 marks

Answer: C

This question in 0971/12 May/June 2025

14 Which experiment is the most exothermic? initial final temperature / °C temperature / °C A 20 5 B 20 32 C 25 12 D 25 34

1 marks

Answer: B

This question in 0971/12 Oct/Nov 2025

38 Which statement about ethanol explains why it is used as a fuel? A It is a colourless liquid. B It has a low density. C It forms carbon dioxide when burned. D It releases energy when burned.

1 marks

Answer: D

This question in 0971/12 Oct/Nov 2025