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AQA GCSE · Question 04.5 · Quantitative chemistry
A different student repeated steps 1 to 5 of the method four times using 0.50 g of zinc powder.
Table 2 shows the results.
<br/><br/>
<table border="1" cellpadding="12" cellspacing="0" style="border-collapse: collapse; font-family: Arial, sans-serif; font-size: 15px; border: 2px solid black;">
<caption style="font-weight: bold; font-size: 18px; margin-bottom: 10px;">Table 2</caption>
<tr>
<th style="border: 1px solid black; padding: 12px;"></th>
<th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">Trial 1</th>
<th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">Trial 2</th>
<th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">Trial 3</th>
<th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">Trial 4</th>
</tr>
<tr>
<td style="border: 1px solid black; padding: 12px; font-weight: bold;">Highest temperature reached in °C</td>
<td style="border: 1px solid black; padding: 12px; text-align: center;">37.6</td>
<td style="border: 1px solid black; padding: 12px; text-align: center;">37.2</td>
<td style="border: 1px solid black; padding: 12px; text-align: center;">37.8</td>
<td style="border: 1px solid black; padding: 12px; text-align: center;">37.4</td>
</tr>
</table>
<br/><br/>
Calculate the mean highest temperature reached.
Include the uncertainty in your answer.
A different student repeated steps 1 to 5 of the method four times using 0.50 g of zinc powder.
Table 2 shows the results.
<br/><br/>
Calculate the mean highest temperature reached.
Include the uncertainty in your answer.
How to approach this question
1. **Calculate the mean:** Add all the temperature values together and divide by the number of values (which is 4).
2. **Calculate the range:** Find the difference between the highest and lowest temperature values.
3. **Calculate the uncertainty:** The uncertainty is half the range.
4. **Write the final answer:** State the mean followed by the ± symbol and the uncertainty value.
Full Answer
Mean = (37.6 + 37.2 + 37.8 + 37.4) / 4 = 149.0 / 4 = 37.5 °C
Range = 37.8 - 37.2 = 0.6 °C
Uncertainty = Range / 2 = 0.6 / 2 = 0.3 °C
Answer: 37.5 ± 0.3 °C
**1. Calculate the mean:**
The mean is the sum of the values divided by the count of the values.
Mean = (37.6 + 37.2 + 37.8 + 37.4) / 4
Mean = 149.0 / 4
Mean = 37.5 °C
**2. Calculate the uncertainty:**
Uncertainty in a set of repeat measurements is calculated as half the range.
Range = Highest value - Lowest value
Range = 37.8 - 37.2 = 0.6 °C
Uncertainty = Range / 2
Uncertainty = 0.6 / 2 = 0.3 °C
**3. Combine the results:**
The result is written as the mean ± uncertainty.
Mean highest temperature = 37.5 ± 0.3 °C
Common mistakes
✗ Forgetting to calculate the uncertainty.
✗ Calculating the range but not halving it for the uncertainty.
✗ Rounding the mean incorrectly.
Practice the full AQA GCSE Chemistry Higher Tier Paper 1
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