Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 362 · 40 questions

What you do (Heat shows the secret): 1. Dip a cotton bud in lemon juice and write a secret message on white paper. 2. Let the paper dry completely — the writing disappears. 3. An adult irons the paper on a low setting while you watch from a safe distance. 4. Read the brown message and wash your hands.

1. 1.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) whoever is fastest (c) the youngest child (d) only an adult
2. 2.True or false: ironing the paper is a job a child can do. (a) False (b) True
3. 3.True or false: writing the message is a job a child can do. (a) True (b) False
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the kind of juice (c) how dark the writing is (d) the iron setting
5. 5.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
6. 6.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) cutting the lemon (d) dipping the cotton bud
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) False (b) True
8. 8.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) rub your eyes (c) lick your fingers (d) wash your hands
9. 9.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
10. 10.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
11. 11.True or false: letting the paper dry is a job a child can do. (a) False (b) True
12. 12.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we keep it the same (c) we measure it
14. 14.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
15. 15.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) blue (d) white
16. 16.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we keep it the same (c) we measure it
18. 18.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) turmeric powder (c) yeast (d) a balloon
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) False (b) True
20. 20.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) it gets darker (c) writing turns green (d) writing stays faint
21. 21.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) yeast (c) white paper (d) an adult with an iron
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) False (b) True
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) True (b) False
24. 24.True or false: reading the message is a job for an adult. (a) True (b) False
25. 25.🔍 Which is the odd one out? (a) writing the message (b) letting the paper dry (c) plugging in the iron (d) dipping the cotton bud
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we keep it the same (c) we measure it
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a magnet (c) lemon juice (d) white paper
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) False (b) True
29. 29.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) paper turns lemony (c) the juice scorches first (d) the iron is brown
30. 30.True or false: plugging in the iron is a job for an adult. (a) False (b) True
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) how dark the writing is (c) the kind of juice
32. 32.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
33. 33.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
34. 34.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
35. 35.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) blue words (c) a rainbow (d) dark brown words
36. 36.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the ink is magnetic (c) the paper ate it (d) dry juice is see-through
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the ironing time (c) the kind of juice
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) False (b) True
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the kind of juice (c) the iron setting
40. 40.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed

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