Models, Claims, Evidence & Reasoning — Practice · Grade 7 Science

Chapter: Scientific Inquiry & Diversity of Life

What this practice covers

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

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

Vocabulary used: claim, evidence, reasoning, model, limitation.

Problem 1

Which part of “the soil is wet because it rained” is an inference?
Answer and explanation

The proposed rainfall cause is an inference; wet soil is the stated observation. Watering or another source could also explain it.

Problem 2

How is reasoning different from listing numbers?
Answer and explanation

Reasoning explains a scientific connection between the observations and the claim. Numbers become relevant evidence through that connection.

Problem 3

Why should a model have a legend?
Answer and explanation

A legend explains what symbols represent so readers can distinguish meaningful relationships from invented display choices.

Problem 4

Does naming a limitation make an explanation worthless?
Answer and explanation

No. It makes the conclusion more accurate and identifies what further evidence would strengthen or change it.

Problem 5

Illustrative observation: covered soil loses 5 g over a day; uncovered soil loses 12 g in the same setting. Starting water, container, and temperature are stated comparable. A claim says a cover always prevents all evaporation. Write a better claim, cite numerical evidence, explain a plausible mechanism, and identify a limit.
Answer and explanation

The cover is associated with 7 g less measured water loss in this comparison. Reducing exposed soil can reduce evaporation under comparable conditions, but the covered sample still lost 5 g. The record therefore does not support “all evaporation prevented” or “always.” Repeated matched trials and checks for other loss pathways would strengthen the explanation.

Calculate the measured loss difference: 12−5=7 g.

State reduced loss in the observed setting.

Connect the cover with reduced exposure under the model.

Notice that 5 g was still lost and other settings were not tested.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 6

A student changes a model after repeated contradictory observations. Is this automatically dishonest?
Answer and explanation

No. Revising a model in response to accurately recorded evidence is part of science. Concealing or inventing observations would be a different problem.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 7

Which is evidence rather than a causal explanation?
  1. The cover reduces exposure
  2. The covered sample lost 5 g
  3. The method is perfect
  4. All evaporation stopped
Answer and explanation

The covered sample lost 5 g

The measured 5 g loss is evidence; explanations and universal conclusions need further reasoning.

Problem 8

Uncovered loss is 15 g and covered loss is 6 g. Find the difference.
Answer and explanation

9 g

15−6=9 g less measured loss.

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