School & debate · Domain Expert
Science fair judge questions: practice with a retired chemist
Judges usually ask what question you tested and why, what your independent and dependent variables were, how you controlled everything else, how many trials you ran, what your data shows, and what you would change or test next. Answer in plain words, point to your graph, and be honest about your project’s limits; judges reward understanding over polish. Practice with Dr. Martin Greaves, a retired chemist who asks how you made sure salt was the only difference between your groups.
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Updated October 2026
Who it's for
Who this practice is for
- High school students preparing for a science fair in January through March.
- Parents helping their teen get ready for judge questions without doing the project for them.
- Science teachers running practice rounds before the fair.
- Anyone who freezes when an adult asks how they know their results are real.
What happens
How a session goes
- Dr. Martin Greaves speaks first, asking how you made sure salt was the only difference between your groups.
- He probes your variables, controls, data, and what you would change, pushing on weak spots.
- At the end, he says what he now understands and gives his decision, like a real judge.
Real lines from a test session
What Dr. Martin Greaves said in a test session
“How did you make sure the only difference between your groups was the salt?”
“Right, so you're not sure. That's an honest answer.”
“Well, you've given a very honest and thoughtful answer. I appreciate that you're now able to see the gaps in your own work. That's exactly what a good scientist does. So here's my final take.”
From a test session of this practice in the app, lightly trimmed. Your session goes its own way: the character reacts to what you say.
The scorecard
What the scorecard looked like for Science Fair Judge Questions
“I did my best. I used the same kind of radish seeds from the same packet. Each pot had the same amount of potting soil and got the same amount of light.”
You listed controls without naming them as 'controlled variables' or stating the independent variable (salt level), which left your experimental design half-descriptive.
Try instead: “My independent variable was the salt concentration in the water, at four levels. The dependent variable was seedling height. I kept everything else the same: same seed packet, same soil, same light.”
What went well: Owned your limitations matter-of-factly (e.g., 'I didn't test the soil' and 'I just pulled them out'), building credibility rather than defending weak spots.
Real scorecard output from one of our test runs. In test runs the practice answers are written by a test script, not by a customer.
What good looks like
What a strong answer does here
- You name the independent variable (salt level), dependent variable (seedling growth), and controlled variables clearly.
- You describe your data honestly: 3 trials, 40 radish seedlings, 4 salt levels, and what you actually saw.
- You explain what you would change next time, like more trials or better control of light and water.
- You say 'I don't know' when you truly don't, instead of overclaiming or reciting your display board.
Scored on:
- Clarity
- Domain Mastery
- Analogy & Simplification
- Value & Persuasion
Common mistakes
Weak lines, and what to say instead
Weak: “I think salt definitely slows growth because my plants looked smaller.”
Better: “In my 3 trials with 40 radish seedlings, the higher salt levels had shorter average heights, but I did not measure root length.”
A judge wants data, not a guess.
Weak: “I controlled everything, so my results are perfect.”
Better: “I kept water, light, and soil the same, but I could not control the room temperature perfectly.”
Admitting a limit shows honesty, not weakness.
Weak: “My display board says the salt made the plants die.”
Better: “My display board summarizes the averages, but I can explain the raw numbers if you want.”
Memorized board text sounds rehearsed, not thoughtful.
Weak: “I don't know why the low salt group grew taller.”
Better: “I am not sure why the low salt group grew taller. That is one thing I would test again with more trials.”
Saying 'I don't know' plus a next step shows scientific thinking.
Science Fair Judge Questions: start talking in a few seconds. Your own side stays yours to fill in.
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Your domain expert practice plan
- Adapt the explanation to your audience
- Use an accurate example or analogy
- Check understanding and answer objections
Start with a free worksheet, then test your own response with a voice or text roleplay. Your first complete coaching report is free once across all areas. Create a free account to save your goal, actual words, and downloadable notes.
Need repeated practice? $4.99 once buys 100 rounds across every mode and full coaching on every report. Rounds never expire; no subscription is required.
FAQ
Questions about Science Fair Judge Questions
What kind of questions will Dr. Greaves ask?
He asks about your variables, controls, and results. For example, how you made sure salt was the only difference between groups. He also asks what you would change and where your project has limits. He speaks first and keeps probing until he understands your work. Try it free →
Will he be mean or discouraging?
No. He is a retired chemist judging the fair, so he is probing but fair. He pushes on weak points to see if you really know your project. In a test session, he said an honest answer was exactly what a good scientist does. Try it free →
How long should my science fair presentation be?
Usually two to five minutes for your summary, then questions, but check your fair’s rules. Start with your question and result in one sentence, walk through your method and data, and finish with what you learned. Judges often stop you early, so lead with the most important part. Try it free →
What if a judge asks something I don't know?
Say so honestly, then reason out loud: “I didn’t test that, but I’d expect… because…” Judges are checking whether you understand your project, and a thoughtful guess with your reasoning is better than a made-up answer. Try it free →
Try Science Fair Judge Questions free
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