Measurements, Models & Evidence — Drills · Grade 9 Science

Chapter: Investigating Earth

What these drills covers

By the end of Measurements, Models & Evidence you should be able to:

8 questions, written answer, numeric and multiple choice, each with a worked explanation.

Vocabulary used: observation, inference, uncertainty.

Problem 1

What should you read before using a scientific chart?
Answer and explanation

Its title, axes, units, key, and applicable conditions.

Problem 2

Readings are 4, 7, and 10. What is the range width?
Answer and explanation

6

10 − 4 = 6.

Problem 3

A measurement repeated five times gives nearly identical values but all differ from a known standard. The measurements are
  1. accurate but not precise
  2. precise but not accurate
  3. both
  4. neither
Answer and explanation

precise but not accurate

Agreement among repeats is precision; agreement with the standard is accuracy.

Problem 4

Readings are 12.1, 12.3 and 12.2 cm. What is the mean, to one decimal place?
Answer and explanation

12.2 cm

(12.1 + 12.3 + 12.2)/3 = 12.2 cm.

Problem 5

For readings 12.1, 12.3 and 12.2 cm, what is the range, to one decimal place?
Answer and explanation

0.2 cm

12.3 − 12.1 = 0.2 cm, which should be reported alongside the mean.

Problem 6

A model of Earth's interior is useful mainly because it
  1. is exactly correct
  2. organises evidence and makes testable predictions
  3. replaces measurement
  4. is simple to draw
Answer and explanation

organises evidence and makes testable predictions

A model's value lies in what it predicts and how it can be checked.

Problem 7

Distinguish an observation from an inference using a rock containing marine shells on a mountain.
Answer and explanation

The observation is that the rock contains shells of marine organisms and is now at high altitude. The inference is that the rock formed on a sea floor and was later uplifted. The first is what anyone can verify directly; the second is a conclusion drawn from it using what we know about where such shells form.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

Problem 8

Why should a scientific claim state its uncertainty?
Answer and explanation

Every measurement has a limit to its precision, so a value without an uncertainty implies more confidence than the evidence supports and cannot be properly compared with another value. Stating the uncertainty shows whether two results genuinely differ or merely overlap, and tells a reader what further measurement would be needed to distinguish them.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

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