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Science lesson plan · 9th grade (Year 10 in England) · 45 minutes

Accuracy, precision, errors and significant figures

Working scientifically

CCSS NGSS.SEP 5CCSS NGSS.HS-PS1-7England: KS4 Working scientificallyEngland: KS4 Combined Science: Working scientifically

Objective and success criteria

Students will: Accuracy, precision, errors and significant figures.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Repeat readings, means and anomalies; Converting units

Leads to: the next skill in this area.

Materials: Simple equipment for a fair test, Results table template, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 5 min

  • Quick retrieval from earlier learning (Repeat readings, means and anomalies; Converting units). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. A group measured a pulse rate after exercise three times: 110, 107 and 109 bpm. What is the mean? Give your answer to 1 decimal place. → 108.7 bpmPrompt: Add the three readings.
  2. Convert 5 km into m. → 5000 mPrompt: How many m are in 1 km?
  3. Four repeat readings of a pulse rate after exercise (bpm): 125, 123, 77, 127. Which reading is anomalous (does not fit the pattern)? (77 / 127 / 125 / 123) → 77Prompt: Most of the readings are close together.

Hook · 5 min

  • Show a simple experiment with one thing changed and ask what makes it a fair test.
  • Share the objective: Accuracy, precision, errors and significant figures. Read the success criteria together.

I do: model it · 10 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: A balance shows 0.3 g when nothing is on it. What kind of error is this?
  • Step 1: A scale that does not start at zero adds the same error every time: a systematic (zero) error.
  • Step 2: So the answer is: a zero error (a systematic error)
  • Answer: a zero error (a systematic error)
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 10 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. Readings of the same length: 12.1, 12.1, 12.2, 12.1 cm. The true length is 13.0 cm. The readings are… (accurate and precise / accurate but not precise / precise but not accurate / neither repeatable nor close) → precise but not accuratePrompt: Precise means close to each other. Accurate means close to the true value.
  2. A balance reads 0.3 g with nothing on it. With a rock on it, it reads 23.7 g. What is the true mass of the rock, in g? → 23.4 gPrompt: The zero error is included in every reading.

You do: independent practice · 10 min

  • Students work on the student sheet. Circulate and check the first two answers of every student early.
  • Students who finish: write a question of their own for a partner, with the answer.

The 8 questions are on the student sheet below, with answers in the key.

Exit ticket · 5 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. A balance reads −0.2 g with nothing on it. With a rock on it, it reads 32.3 g. What is the true mass of the rock, in g? → 32.5 gPrompt: The zero error is included in every reading.
  2. A calculator gives a density of 6431.9. Write it to 2 significant figures. → 6400Prompt: Count from the first non-zero digit.

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: Repeat readings, means and anomalies.
  • Use concrete materials: simple equipment for a fair test.
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-9.

Free lesson plan from eurekami.com/lesson-plan-builder

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Accuracy, precision, errors and significant figures

Name

Date

Score/ 8

  1. Question 1

    What is the resolution of a ruler marked in millimetres?

    • A. 0.1 mm
    • B. 1 mm
    • C. 1 cm
    • D. 1 m

  2. Question 2

    A balance reads 0.3 g with nothing on it. With a rock on it, it reads 54.2 g. What is the true mass of the rock, in g?

    Answerg

  3. Question 3

    A calculator gives a density of 3795.9. Write it to 3 significant figures.

    Answer

  4. Question 4

    Timing a falling ball by hand gives slightly different values each time. This is mainly due to…

    • A. random error (human reaction time)
    • B. a zero error
    • C. gravity switching off
    • D. the ball changing mass

  5. Question 5

    A balance reads 0.4 g with nothing on it. With a rock on it, it reads 45.2 g. What is the true mass of the rock, in g?

    Answerg

  6. Question 6

    A calculator gives a density of 0.48889. Write it to 2 significant figures.

    Answer

  7. Question 7

    A balance reads 0.5 g with nothing on it. With a rock on it, it reads 11 g. What is the true mass of the rock, in g?

    Answerg

  8. Question 8

    A calculator gives a density of 3017.3. Write it to 2 significant figures.

    Answer

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Answer key: Accuracy, precision, errors and significant figures

  1. 1. B. 1 mm

  2. 2. 53.9 g

  3. 3. 3800

  4. 4. A. random error (human reaction time)

  5. 5. 44.8 g

  6. 6. 0.49

  7. 7. 10.5 g

  8. 8. 3000