News by Levels · Level 3 · For teachers
Teacher guide & answers
A Positron Experiment Prepares a Symmetry Test
How to use these two pages
Give learners the student worksheet. It contains the story and questions, without the answers. Keep this guide for yourself. Use it to lead the activity and explain the answers afterwards.
Student worksheetA simple 15–20-minute lesson
- Before reading · 2 minutes
Show the title. Ask: “What do you think this story is about?”
- Read and answer · 8–10 minutes
Give out the student worksheet. Learners read for the main idea, then reread to answer the 2 questions. They can compare answers with a partner.
- Discuss and write · 5–8 minutes
Check the answers below together. Ask learners to point to the clue in the story, then finish with the open question.
Adjust the support: Let learners use word help or Level 1 if needed. For a challenge, compare the wording in another level. This activity is not a proficiency test.
Answers to the 2 questions
The question numbers match the student worksheet. Each answer includes a reason and the clue learners can find in the story.
What has the trapping achievement made possible?
Correct answer: A — A later precise comparison
Why: Control provides a means of testing, not the eventual answer.
Clue in the story: Experimental control is an enabling achievement, distinct from a test’s eventual conclusion. The trapping technique supplies access to the system under investigation; it does not itself establish a discrepancy between particle properties or a failure of the theoretical framework.
What would a claim of differing properties require?
Correct answer: B — Measurements and comparison
Why: A property difference must be established through the relevant measurements.
Clue in the story: Experimental control is an enabling achievement, distinct from a test’s eventual conclusion. The trapping technique supplies access to the system under investigation; it does not itself establish a discrepancy between particle properties or a failure of the theoretical framework.
The open question: accept different answers
Ask learners: Distinguish a new experimental tool from a new result about particle properties.
One possible answer: The trap lets scientists control a particle. Measurements using that control are still needed to establish whether its properties differ from expectations.
This is an example, not the only correct answer. Look for a relevant idea, a reason and the learner’s own words. Learners can answer aloud or write one or two sentences.