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Science lesson plan · 9th grade (Year 10 in England) · 60 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 · 6 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 how far a toy car travelled three times: 74, 72 and 71 cm. What is the mean? Give your answer to 1 decimal place. → 72.3 cmPrompt: Add the three readings.
  2. Convert 12 km into m. → 12000 mPrompt: How many m are in 1 km?
  3. Four repeat readings of how far a toy car travelled (cm): 117, 88, 88, 86. Which reading is anomalous (does not fit the pattern)? (117 / 88 / 86) → 117Prompt: Most of the readings are close together.

Hook · 6 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 · 12 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 · 12 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. What is the resolution of a ruler marked in millimetres? (1 mm / 1 m / 1 cm / 0.1 mm) → 1 mmPrompt: Resolution is the smallest change the instrument can show.
  2. A balance reads −0.3 g with nothing on it. With a rock on it, it reads 47.5 g. What is the true mass of the rock, in g? → 47.8 gPrompt: The zero error is included in every reading.

You do: independent practice · 17 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 · 7 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. A calculator gives a density of 0.041001. Write it to 2 significant figures. → 0.041Prompt: Count from the first non-zero digit.
  2. 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 / precise but not accurate / neither repeatable nor close / accurate but not precise) → precise but not accuratePrompt: Precise means close to each other. Accurate means close to the true value.

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

    A balance reads 0.3 g with nothing on it. With a rock on it, it reads 29 g. What is the true mass of the rock, in g?

    Answerg

  2. Question 2

    Readings of the same length: 12.1, 12.1, 12.2, 12.1 cm. The true length is 13.0 cm. The readings are…

    • A. accurate but not precise
    • B. neither repeatable nor close
    • C. precise but not accurate
    • D. accurate and precise

  3. Question 3

    A calculator gives a density of 0.058662. Write it to 3 significant figures.

    Answer

  4. Question 4

    A balance reads −0.2 g with nothing on it. With a rock on it, it reads 21.2 g. What is the true mass of the rock, in g?

    Answerg

  5. Question 5

    A balance shows 0.3 g when nothing is on it. What kind of error is this?

    • A. a zero error (a systematic error)
    • B. an anomalous result
    • C. no error
    • D. a random error

  6. Question 6

    A calculator gives a density of 3617.8. Write it to 2 significant figures.

    Answer

  7. Question 7

    A balance reads 0.2 g with nothing on it. With a rock on it, it reads 30.2 g. What is the true mass of the rock, in g?

    Answerg

  8. Question 8

    A calculator gives a density of 66.642. Write it to 3 significant figures.

    Answer

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Answer key: Accuracy, precision, errors and significant figures

  1. 1. 28.7 g

  2. 2. C. precise but not accurate

  3. 3. 0.0587

  4. 4. 21.4 g

  5. 5. A. a zero error (a systematic error)

  6. 6. 3600

  7. 7. 30 g

  8. 8. 66.6