Significant figures
👩 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
📝 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.
💬 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?
🧒 Student Worksheet
Concept and Helping Material
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Significant figures show how precise a measurement is. Using them correctly stops you from claiming unrealistic accuracy when your measuring tools cannot support it.
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.
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?
Practice Questions (QA)
- What do significant figures tell you?
- Round 3.746 to 3 significant figures.
- Round 0.004560 to 2 significant figures.
- In multiplication, how do you decide sig figs in the answer?
- Why not keep all calculator digits?
- How many significant figures are in 1200 (no decimal point)?
- How many significant figures are in 1200.?
- Round 15.0 to 2 significant figures.
- If a measurement is 2.30 cm, how many sig figs is that?
- Why should rounding usually be done at the end?
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?