Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 626 · 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.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) False (b) True
3. 3.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) the youngest child (c) only an adult (d) whoever is fastest
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we measure it (c) we change it
5. 5.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
6. 6.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the iron setting (c) the same cotton bud (d) the same paper
8. 8.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) turmeric powder (c) a battery cell (d) a mirror
9. 9.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
10. 10.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
11. 11.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if cooled (c) yes, in the dark (d) yes, if shaken
12. 12.True or false: white paper is needed for the secret lemon message. (a) True (b) False
13. 13.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) heat adds colour (d) the juice scorches first
14. 14.⚖️ 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 measure it (c) we keep it the same
15. 15.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) white paper (c) yeast (d) a cotton bud
16. 16.🧺 Which of these is needed for the secret lemon message? (a) white paper (b) a battery cell (c) a balloon (d) a magnet
17. 17.True or false: ironing the paper is a job a child can do. (a) True (b) False
18. 18.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a small bowl (c) white paper (d) a battery cell
19. 19.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
20. 20.True or false: writing the message is a job a child can do. (a) False (b) True
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) the same cotton bud (c) the ironing time (d) the kind of juice
22. 22.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
23. 23.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is cold (c) it is magnetic (d) it can burn skin
24. 24.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same cotton bud (b) the kind of juice (c) how dark the writing is
26. 26.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
27. 27.⚖️ 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
28. 28.True or false: writing the message is a job for an adult. (a) False (b) True
29. 29.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) dry juice is see-through (c) the ink is magnetic (d) it turned into air
30. 30.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
31. 31.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) writing the message (d) putting the iron away
32. 32.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
33. 33.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) False (b) True
35. 35.True or false: ironing the paper is a job for an adult. (a) True (b) False
36. 36.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a small bowl (c) an adult with an iron (d) a mirror
37. 37.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) white paper (c) turmeric powder (d) an adult with an iron
38. 38.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) the paper floats (c) writing stays faint (d) writing turns green
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we measure it (c) we change it
40. 40.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) dark brown words (c) a rainbow (d) almost nothing

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