Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 691 · 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.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) the ink is magnetic (c) it turned into air (d) dry juice is see-through
2. 2.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) paper turns lemony (c) the iron is brown (d) the juice scorches first
3. 3.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
4. 4.True or false: reading the message is a job for an adult. (a) False (b) True
5. 5.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) ironing the paper (d) dipping the cotton bud
6. 6.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) almost nothing (c) a rainbow (d) blue words
7. 7.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) an adult with an iron (c) a balloon (d) turmeric powder
8. 8.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
9. 9.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
10. 10.⚖️ 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 change it (c) we measure it
11. 11.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) reading the message (c) putting the iron away (d) ironing the paper
12. 12.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if shaken (c) yes, in the dark (d) yes, if cooled
13. 13.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) reading the message (d) putting the iron away
14. 14.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) lemon juice (c) turmeric powder (d) white paper
15. 15.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) letting the paper dry (c) putting the iron away (d) ironing the paper
16. 16.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a small bowl (c) turmeric powder (d) a battery cell
17. 17.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a small bowl (c) yeast (d) an adult with an iron
18. 18.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) the paper floats (d) writing stays faint
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we keep it the same (b) we measure it (c) we change it
20. 20.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) the same cotton bud (c) how dark the writing is (d) the ironing time
22. 22.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
23. 23.True or false: letting the paper dry is a job for an adult. (a) False (b) True
24. 24.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) lemon juice (c) a battery cell (d) an adult with an iron
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) lemon juice (c) a cotton bud (d) white paper
26. 26.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
27. 27.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
28. 28.True or false: plugging in the iron is a job a child can do. (a) True (b) False
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) False (b) True
30. 30.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) lemon juice (c) a balloon (d) a mirror
31. 31.🔍 Which is the odd one out? (a) putting the iron away (b) reading the message (c) writing the message (d) dipping the cotton bud
32. 32.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a mirror (c) lemon juice (d) a cotton bud
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the iron setting (b) the ironing time (c) the kind of juice (d) how dark the writing is
34. 34.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) writing the message (c) cutting the lemon (d) plugging in the iron
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we change it (c) we keep it the same
36. 36.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a magnet (c) white paper (d) a mirror
37. 37.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) white paper (c) turmeric powder (d) a cotton bud
38. 38.True or false: a magnet is not needed for the secret lemon message. (a) True (b) False
39. 39.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) lick your fingers (c) wash your hands (d) rub your eyes
40. 40.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed

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