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This question is about energy change - AQA - GCSE Chemistry Combined Science - Question 3 - 2021 - Paper 1
Question 3
This question is about energy change. A student investigated the temperature change when 10 g of ammonium nitrate was added to 100 cm³ of water. This is the method ... show full transcript
Worked Solution & Example Answer:This question is about energy change - AQA - GCSE Chemistry Combined Science - Question 3 - 2021 - Paper 1
Step 1
Step 2
Give three improvements to the investigation to make the results more accurate.
Answer
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Insulate the beaker with a polystyrene cup to reduce heat loss.
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Use a larger mass of ammonium nitrate to ensure a more significant temperature change.
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Use a more accurate thermometer to obtain precise temperature measurements.
Step 3
Explain the results.
Answer
From 0 to 1.5 minutes, the temperature decreases because ammonium nitrate dissolving is an endothermic process. This means it absorbs heat from the surroundings, causing the temperature to drop from 21.4 °C to 15.4 °C. After 1.5 minutes, the temperature increases slightly as the solution comes to equilibrium, indicating a balance between endothermic dissolution and the heat gained from the surroundings.
Step 4
Draw a reaction profile for an exothermic reaction.
Answer
The reaction profile should have:
- A label for the energy level of the reactants at a higher position.
- A labeled activation energy line showing the energy barrier.
- A line dropping down to the product level, which should be lower than the reactant level, indicating the overall energy change is negative, representative of an exothermic reaction.