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Science lesson plan · 9th grade (Year 10 in England) · 30 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 · 4 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 the time for a ball to roll down a ramp three times: 35, 32 and 32 s. What is the mean? Give your answer to 1 decimal place. → 33 sPrompt: 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): 34, 66, 62, 65. Which reading is anomalous (does not fit the pattern)? (34 / 66 / 62 / 65) → 34Prompt: Most of the readings are close together.

Hook · 3 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 · 7 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 · 6 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… (precise but not accurate / accurate and precise / accurate but not precise / 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 0.2 g with nothing on it. With a rock on it, it reads 10.3 g. What is the true mass of the rock, in g? → 10.1 gPrompt: The zero error is included in every reading.

You do: independent practice · 7 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 6 questions are on the student sheet below, with answers in the key.

Exit ticket · 3 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. A balance reads 0.5 g with nothing on it. With a rock on it, it reads 32.1 g. What is the true mass of the rock, in g? → 31.6 gPrompt: The zero error is included in every reading.
  2. A calculator gives a density of 896.37. Write it to 2 significant figures. → 900Prompt: 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

eurekami

Accuracy, precision, errors and significant figures

Name

Date

Score/ 6

  1. Question 1

    A calculator gives a density of 702.79. Write it to 2 significant figures.

    Answer

  2. Question 2

    A balance reads −0.2 g with nothing on it. With a rock on it, it reads 50.7 g. What is the true mass of the rock, in g?

    Answerg

  3. Question 3

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

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

  4. Question 4

    A calculator gives a density of 0.043604. Write it to 2 significant figures.

    Answer

  5. Question 5

    A balance reads 0.3 g with nothing on it. With a rock on it, it reads 17.5 g. What is the true mass of the rock, in g?

    Answerg

  6. Question 6

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

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Answer key: Accuracy, precision, errors and significant figures

  1. 1. 700

  2. 2. 50.9 g

  3. 3. D. random error (human reaction time)

  4. 4. 0.044

  5. 5. 17.2 g

  6. 6. A. precise but not accurate