Comparing scientific explanations (conflicting viewpoints)

Working scientifically

CCSS NGSS.SEP 7CCSS NGSS.SEP 8England: KS4 Working scientifically

Objective and success criteria

Students will: Comparing scientific explanations (conflicting viewpoints).

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: Evaluating experiments (research summaries)

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 (Evaluating experiments (research summaries)). Students answer on mini whiteboards.
Show answers together and note who needs support in the main task.

Experiment 1: A pendulum with a 0.5 kg bob was timed for 10 swings with string lengths of 0.25 m, 0.50 m and 1.00 m. Experiment 2: A 1.00 m pendulum was timed with bobs of 0.1 kg, 0.5 kg and 1.0 kg. In Experiment 2, which variable was changed on purpose? (the time for 10 swings / the mass of the bob / the temperature of the room / the string length) → the mass of the bobPrompt: Look only at the description of Experiment 2.
Experiment 1: Magnesium ribbon was added to hydrochloric acid at concentrations of 0.5, 1.0 and 2.0 mol/dm³ at 25 °C, and the gas volume after 1 minute was measured. Experiment 2: The 1.0 mol/dm³ acid was used at 15 °C, 25 °C and 35 °C. Which variable was kept constant in Experiment 2 but changed in Experiment 1? (the temperature / the volume of gas after 1 minute / the acid concentration / the colour of the magnesium) → the acid concentrationPrompt: What was tested in Experiment 1?
A scientist tests a new fertiliser on 20 tomato plants. Another 20 plants get no fertiliser. What is the purpose of the second group? (It is a control group to compare against. / It increases the dependent variable. / It makes the experiment faster. / It is not needed.) → It is a control group to compare against.Prompt: How would you know the fertiliser made a difference?

Hook · 5 min

Show a simple experiment with one thing changed and ask what makes it a fair test.
Share the objective: Comparing scientific explanations (conflicting viewpoints). 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: Two students explain why a ball rolling on a flat floor eventually stops. Student 1: Objects naturally slow down and stop when nothing keeps pushing them. Student 2: Friction and air resistance act against the motion; with no resistive forces, the ball would keep moving at a steady speed. Which student's view agrees with Newton's first law?
Step 1: Newton's first law: an object keeps moving at constant velocity unless a resultant force acts.
Step 2: So the answer is: Student 2
Answer: Student 2
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.

What makes a scientific explanation stronger than another? (It explains more of the evidence and makes predictions that are confirmed / More people like it / It is more complicated / It is older) → It explains more of the evidence and makes predictions that are confirmedPrompt: Scientists judge ideas by evidence.
Two scientists explain why the Moon shows phases. Scientist 1: Earth's shadow covers different amounts of the Moon during the month. Scientist 2: Half of the Moon is always lit by the Sun; as the Moon orbits Earth, we see different amounts of the lit half. Which scientist's explanation is accepted by astronomers today? (both / Scientist 2 / neither / Scientist 1) → Scientist 2Prompt: Read each viewpoint and underline its key claim.

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.

A new observation contradicts a well-tested theory. What usually happens? (Science stops / Scientists check the observation, then improve or replace the theory if it holds up / The theory is never changed / The observation is always thrown away) → Scientists check the observation, then improve or replace the theory if it holds upPrompt: Science changes when evidence changes.
Two students explain why a ball rolling on a flat floor eventually stops. Student 1: Objects naturally slow down and stop when nothing keeps pushing them. Student 2: Friction and air resistance act against the motion; with no resistive forces, the ball would keep moving at a steady speed. The ball rolls much further on smooth ice than on carpet. This result… (supports neither student / supports Student 1 / shows friction makes things faster / supports Student 2) → supports Student 2Prompt: Read each viewpoint and underline its key claim.

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: Evaluating experiments (research summaries).
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-11.

Free lesson plan from eurekami.com/lesson-plan-builder

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Comparing scientific explanations (conflicting viewpoints)

Name

Date

Score/ 8

1
Question 1
Two hypotheses explain the same data. How can scientists decide between them?
- A. Vote on them
- B. Ignore the data
- C. Choose the shorter one
- D. Design an experiment where they predict different results
2
Question 2
Two scientists explain why the Moon shows phases. Scientist 1: Earth's shadow covers different amounts of the Moon during the month. Scientist 2: Half of the Moon is always lit by the Sun; as the Moon orbits Earth, we see different amounts of the lit half. Which scientist's explanation is accepted by astronomers today?
- A. both
- B. neither
- C. Scientist 1
- D. Scientist 2
3
Question 3
Two scientists explain why some lakes have fewer fish than ten years ago. Scientist 1: Farm fertiliser washed into the lakes caused algae to grow; when the algae died, bacteria used up the oxygen in the water. Scientist 2: Warmer water from climate change holds less dissolved oxygen, so fewer fish survive. A lake far from any farm also lost fish as it warmed. This supports…
- A. Scientist 2
- B. neither scientist
- C. only that fertiliser is harmless
- D. Scientist 1
4
Question 4
Two students explain why a ball rolling on a flat floor eventually stops. Student 1: Objects naturally slow down and stop when nothing keeps pushing them. Student 2: Friction and air resistance act against the motion; with no resistive forces, the ball would keep moving at a steady speed. Which student's view agrees with Newton's first law?
- A. Student 1
- B. Both
- C. Neither
- D. Student 2
5
Question 5
Two students explain why a metal spoon in hot soup feels hotter than a wooden spoon in the same soup. Student 1: The metal spoon is at a higher temperature than the wooden spoon. Student 2: Both spoons reach a similar temperature at the end in the soup, but metal conducts thermal energy into your hand much faster, so it feels hotter. A thermometer shows the tips of both spoons in the soup at the same temperature. This result supports…
- A. Student 1
- B. neither student
- C. Student 2
- D. both students equally
6
Question 6
A new observation contradicts a well-tested theory. What usually happens?
- A. The observation is always thrown away
- B. The theory is never changed
- C. Science stops
- D. Scientists check the observation, then improve or replace the theory if it holds up
7
Question 7
Peer review means…
- A. the result can never be questioned
- B. other scientists check work before it is published
- C. the scientist checks their own work only
- D. friends vote on the result
8
Question 8
Two students explain why a ball rolling on a flat floor eventually stops. Student 1: Objects naturally slow down and stop when nothing keeps pushing them. Student 2: Friction and air resistance act against the motion; with no resistive forces, the ball would keep moving at a steady speed. The ball rolls much further on smooth ice than on carpet. This result…
- A. supports Student 1
- B. shows friction makes things faster
- C. supports neither student
- D. supports Student 2

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Answer key: Comparing scientific explanations (conflicting viewpoints)

1. D. Design an experiment where they predict different results
2. D. Scientist 2
3. A. Scientist 2
4. D. Student 2
5. C. Student 2
6. D. Scientists check the observation, then improve or replace the theory if it holds up
7. B. other scientists check work before it is published
8. D. supports Student 2