Significant figures
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👩 Teacher’s Guide
🎯 Objective
Students will be able to:
- State what significant figures are and why they matter
- Round values correctly to a stated number of significant figures
- Apply significant figure rules in calculations
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📝 Teaching Notes
- Key idea to emphasize: Main concept: sig figs communicate measurement precision.
- Common misconception: Misconception: more digits always mean a better answer.
- Suggested teaching approach:
- Link sig figs to instrument resolution.
- Practice rounding rules with examples.
- Apply rules to multi-step calculations.
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💬 Discussion Starter
Ask students:
- Why is evidence more important than opinion in science?
- What makes an experiment a “fair test”?
- How can scientists disagree and still make progress?
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🧒 Student Worksheet
Concept and Helping Material
Significant figures show how precise a measurement is. Using them correctly stops you from claiming unrealistic accuracy when your measuring tools cannot support it.
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Vocabulary and Definitions
- — A digit that shows measurement precision.
- — Adjusting a number to fewer digits with rules.
- — The position of a digit after the decimal point.
- — Writing numbers as a × 10^n.
- — The possible range around a measurement.
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Hands-On Experiment or Activities
Activity 1: Sig Fig Rounding Relay
What You Need: rounding cards.
What You Do: Teams round values to 2, 3, or 4 sig figs; check against answer key.
Think and Talk: What changed? What stayed the same?
Activity 2: Calculation Precision Practice
What You Need: calculator, worksheet.
What You Do: Multiply/divide measurements and round final answer to correct sig figs.
Think and Talk: What changed? What stayed the same?
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Practice Questions (QA)
1. What do significant figures tell you?
2. Round 3.746 to 3 significant figures.
3. Round 0.004560 to 2 significant figures.
4. In multiplication, how do you decide sig figs in the answer?
5. Why not keep all calculator digits?
6. How many significant figures are in 1200 (no decimal point)?
7. How many significant figures are in 1200.?
8. Round 15.0 to 2 significant figures.
9. If a measurement is 2.30 cm, how many sig figs is that?
10. Why should rounding usually be done at the end?
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Reflection
- How could significant figures help you make a better decision in real life?
- What is one habit you can practice to improve your scientific thinking?