Let’s solve each question step by step, explaining the key concepts of
accuracy and
precision in chemistry:
---
🔑 Definitions:
-
Accuracy: How close a measured value is to the *true* or *accepted* value.
-
Precision: How close repeated measurements are to *each other* (reproducibility), regardless of whether they’re close to the true value.
---
##
✔ Question 1: Susan’s Experiment
> Susan conducts an experiment five times and gets a solution concentration of
1.9M, 2.1M, 1.8M, 1.9M, and 2.2M. The known concentration of the solution is
2.0M.
Step-by-step:
-
True value = 2.0M
- Her results: 1.8, 1.9, 1.9, 2.1, 2.2 → all within ±0.2M of 2.0M →
close to true value → accurate
- The values are also very close to each other (range = 2.2 - 1.8 = 0.4M) →
consistent with each other → precise
✔ So, her results are
both accurate and precise.
✔️ Correct Answer:
>
They are both accurate and precise.
---
##
✔ Question 2: Martin’s Experiment
> Martin’s yields:
5.2g, 1.3g, 8.5g. Average =
5.0g, which is close to known yield of
5.1g.
Step-by-step:
-
True value = 5.1g
- Average = 5.0g → very close → so
accurate on average
- But individual values: 1.3g, 5.2g, 8.5g → spread out over a wide range (7.2g difference!) →
not consistent → not precise
✔ So, his results are
accurate (on average) but not precise.
✔️ Correct Answer:
>
His results are accurate but not precise.
---
##
✔ Question 3: Jared’s Golf Drives
> Normal driver distance =
250 yards. His three drives:
190, 195, 187 yards.
Step-by-step:
- True/expected value = 250 yards
- His results: 187–195 yards → all around 190 →
far from 250 → not accurate
- But the values are very close to each other (range = 195 - 187 = 8 yards) →
consistent → precise
✔ So, his drives are
precise but not accurate.
✔️ Correct Answer:
>
His drives are precise but not accurate.
---
## 🧾 Final Answers:
1.
They are both accurate and precise.
2.
His results are accurate but not precise.
3.
His drives are precise but not accurate.
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Let me know if you’d like a visual diagram or mnemonic to remember accuracy vs. precision! 🎯📊
Parent Tip: Review the logic above to help your child master the concept of precision and accuracy worksheet.
