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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 the temperature rise in a reaction three times: 14, 13 and 11 °C. What is the mean? Give your answer to 1 decimal place. → 12.7 °CPrompt: Add the three readings.
  2. Convert 8 L into mL. → 8000 mLPrompt: How many mL are in 1 L?
  3. Four repeat readings of a pulse rate after exercise (bpm): 140, 208, 138, 138. Which reading is anomalous (does not fit the pattern)? (208 / 140 / 138) → 208Prompt: 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. Timing a falling ball by hand gives slightly different values each time. This is mainly due to… (a zero error / gravity switching off / the ball changing mass / random error (human reaction time)) → random error (human reaction time)Prompt: The errors are different each time, not the same.
  2. A balance reads −0.2 g with nothing on it. With a rock on it, it reads 31.9 g. What is the true mass of the rock, in g? → 32.1 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 0.3 g with nothing on it. With a rock on it, it reads 58.8 g. What is the true mass of the rock, in g? → 58.5 gPrompt: The zero error is included in every reading.
  2. A calculator gives a density of 406.87. Write it to 3 significant figures. → 407Prompt: 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

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

  2. Question 2

    A balance reads 0.2 g with nothing on it. With a rock on it, it reads 37.2 g. What is the true mass of the rock, in g?

    Answerg

  3. Question 3

    A calculator gives a density of 0.95759. 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. a zero error
    • B. the ball changing mass
    • C. random error (human reaction time)
    • D. gravity switching off

  5. Question 5

    A balance reads −0.3 g with nothing on it. With a rock on it, it reads 16 g. What is the true mass of the rock, in g?

    Answerg

  6. Question 6

    A calculator gives a density of 1439.3. Write it to 2 significant figures.

    Answer

  7. Question 7

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

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

  8. Question 8

    A balance reads 0.4 g with nothing on it. With a rock on it, it reads 26.3 g. What is the true mass of the rock, in g?

    Answerg

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Answer key: Accuracy, precision, errors and significant figures

  1. 1. C. precise but not accurate

  2. 2. 37 g

  3. 3. 0.958

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

  5. 5. 16.3 g

  6. 6. 1400

  7. 7. C. a zero error (a systematic error)

  8. 8. 25.9 g