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 · 6 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: 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. In Experiment 2, which variable was changed on purpose? (the volume of gas after 1 minute / the colour of the magnesium / the temperature / the acid concentration) → the temperaturePrompt: Look only at the description of Experiment 2.
Experiment 1: Seeds were kept at 10 °C, 20 °C and 30 °C, all watered daily, and the number that germinated was counted. Experiment 2: Seeds were kept at 20 °C and given 0, 5 or 10 mL of water a day. Which variable was kept constant in Experiment 2 but changed in Experiment 1? (the temperature / the volume of water / the number of seeds that germinated / the colour of the pots) → the temperaturePrompt: What was tested in Experiment 1?
Hypothesis: "Plants grow faster in blue light than in red light." Which experiment tests it best? (Plants in blue light only / Different species under the same lamp / Identical plants under blue or red lamps of equal brightness, same water and temperature / One plant in blue light outdoors and one in red light indoors) → Identical plants under blue or red lamps of equal brightness, same water and temperaturePrompt: Only the colour of light should differ.

Hook · 6 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 · 12 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 · 12 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 is more complicated / It explains more of the evidence and makes predictions that are confirmed / It is older / More people like it) → 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 1 / Scientist 2 / neither) → Scientist 2Prompt: Read each viewpoint and underline its key claim.

You do: independent practice · 17 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 · 7 min

Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

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… (neither scientist / only that fertiliser is harmless / Scientist 2 / Scientist 1) → Scientist 2Prompt: Read each viewpoint and underline its key claim.
What makes a scientific explanation stronger than another? (It is more complicated / It explains more of the evidence and makes predictions that are confirmed / It is older / More people like it) → It explains more of the evidence and makes predictions that are confirmedPrompt: Scientists judge ideas by evidence.

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

eurekami

Comparing scientific explanations (conflicting viewpoints)

Name

Date

Score/ 8

1
Question 1
Peer review means…
- A. the scientist checks their own work only
- B. the result can never be questioned
- C. other scientists check work before it is published
- D. friends vote on the result
2
Question 2
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. Neither
- B. Student 1
- C. Both
- D. Student 2
3
Question 3
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. Earth's shadow is only on the Moon during a lunar eclipse, which happens at full moon. This evidence weakens…
- A. Scientist 1
- B. Scientist 2
- C. neither scientist
- D. both scientists
4
Question 4
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. Scientists check the observation, then improve or replace the theory if it holds up
- D. Science stops
5
Question 5
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. neither
- B. Scientist 1
- C. both
- D. Scientist 2
6
Question 6
What makes a scientific explanation stronger than another?
- A. It explains more of the evidence and makes predictions that are confirmed
- B. It is more complicated
- C. It is older
- D. More people like it
7
Question 7
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 2
- B. supports Student 1
- C. supports neither student
- D. shows friction makes things faster
8
Question 8
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. What do both scientists agree on?
- A. The water is getting colder.
- B. Fish numbers have increased.
- C. Fertiliser is the only cause.
- D. Low oxygen in the water harms the fish.

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Answer key: Comparing scientific explanations (conflicting viewpoints)

1. C. other scientists check work before it is published
2. D. Student 2
3. A. Scientist 1
4. C. Scientists check the observation, then improve or replace the theory if it holds up
5. D. Scientist 2
6. A. It explains more of the evidence and makes predictions that are confirmed
7. A. supports Student 2
8. D. Low oxygen in the water harms the fish.