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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 temperature rise in a reaction three times: 15, 18 and 17 °C. What is the mean? Give your answer to 1 decimal place. → 16.7 °CPrompt: Add the three readings.
  2. Convert 5 m into cm. → 500 cmPrompt: How many cm are in 1 m?
  3. Four repeat readings of the time for a ball to roll down a ramp (s): 38, 24, 38, 36. Which reading is anomalous (does not fit the pattern)? (24 / 38 / 36) → 24Prompt: 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. A balance shows 0.3 g when nothing is on it. What kind of error is this? (an anomalous result / a zero error (a systematic error) / no error / a random error) → a zero error (a systematic error)Prompt: It shifts every reading by the same amount.
  2. A balance reads 0.3 g with nothing on it. With a rock on it, it reads 25.1 g. What is the true mass of the rock, in g? → 24.8 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 −0.3 g with nothing on it. With a rock on it, it reads 47.8 g. What is the true mass of the rock, in g? → 48.1 gPrompt: The zero error is included in every reading.
  2. A calculator gives a density of 0.42853. Write it to 2 significant figures. → 0.43Prompt: 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/ 6

  1. Question 1

    A calculator gives a density of 0.038605. Write it to 3 significant figures.

    Answer

  2. Question 2

    What is the resolution of a ruler marked in millimetres?

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

  3. Question 3

    A balance reads 0.2 g with nothing on it. With a rock on it, it reads 18.5 g. What is the true mass of the rock, in g?

    Answerg

  4. Question 4

    A calculator gives a density of 860.26. Write it to 2 significant figures.

    Answer

  5. Question 5

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

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

  6. Question 6

    A balance reads 0.2 g with nothing on it. With a rock on it, it reads 16.2 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. 0.0386

  2. 2. C. 1 mm

  3. 3. 18.3 g

  4. 4. 860

  5. 5. B. random error (human reaction time)

  6. 6. 16 g