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Endothermic and Exothermic reactons — Free MYP5 Chemistry Practice Questions
1QuestionEnergy transfer between system and surroundingsConcept Practice
2 marks~3 minCriterion A
A student dissolves ammonium nitrate in water inside a beaker. The thermometer reads , while the surrounding air is at . The beaker feels cold to the touch, and arrows on the diagram show energy transferring from the surroundings into the reaction mixture.
a
Deduce the direction of energy transfer between the surroundings and the reaction mixture. [1]
b
Justify the classification of this reaction as endothermic, using the temperature data provided. [1]
Solutions
2QuestionTemperature changes during reactionsAssessment Practice
5 marks~8 minCriterion B
A student adds 1.0 g samples of five metals to 50 cm³ of 1.0 mol/dm³ hydrochloric acid in a polystyrene cup, recording the maximum temperature change () for each:
An unknown metal X, tested under identical conditions, gives °C.
| Metal | magnesium | zinc | iron | copper | silver |
|---|---|---|---|---|---|
| (°C) | +24.5 | +12.0 | +5.5 | 0.0 | 0.0 |
An unknown metal X, tested under identical conditions, gives °C.
a
State the type of energy change occurring when a reactive metal is added to hydrochloric acid, and write the general word equation for the reaction. [1]
b
Explain how the data above show a relationship between a metal's reactivity and its observed , referring to at least three metals in your answer. [2]
c
Deduce the identity of metal X. Justify your answer using both the data and the reactivity series. [2]
Solutions
3QuestionDefinition of endothermic vs exothermic reactionsAssessment Practice
5 marks~8 minCriterion C
A student mixes 50 cm³ of 1.0 mol dm⁻³ HCl with 50 cm³ of 1.0 mol dm⁻³ NaOH in a polystyrene cup and records the temperature every 30 seconds.
| Time (s) | 0 | 30 | 60 | 90 | 120 | 150 | 180 | 210 | 240 | 270 | 300 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Temperature (°C) | 22.0 | 26.5 | 29.8 | 31.2 | 31.5 | 31.0 | 30.2 | 29.1 | 28.0 | 27.0 | 26.2 |
a
State whether the reaction is endothermic or exothermic. Give one piece of evidence from the data to support your answer. [1]
b
Explain the shape of the temperature–time graph between 0 s and 120 s, and between 120 s and 300 s. [2]
c
Analyse why the temperature decrease after 120 s does not indicate an endothermic process, and evaluate what this means for using temperature change alone to classify a reaction. [2]
Solutions
4QuestionEnergy transfer between system and surroundingsAssessment Practice
6 marks~9 minCriterion D
Single-use hand warmers contain iron powder, water, salt, and activated carbon. When exposed to air, the iron undergoes oxidation:
The reaction releases thermal energy, raising the surface temperature of the warmer to approximately 50–60 °C. Millions of hand warmers are discarded globally each year.
The reaction releases thermal energy, raising the surface temperature of the warmer to approximately 50–60 °C. Millions of hand warmers are discarded globally each year.
a
Explain why this reaction is classified as exothermic, and describe the energy transfer that occurs between the hand warmer (system) and its surroundings. [2]
b
Explain how two different properties of the materials used in hand warmers contribute to environmental concerns when the warmers are disposed of at large scale. [2]
c
Analyse the health risk posed by the surface temperature of the hand warmer during use, and evaluate the effectiveness of one method to reduce this risk. [2]
Solutions
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