Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 671 · 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.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
2. 2.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a mirror (c) an adult with an iron (d) lemon juice
3. 3.🧺 Which of these is not needed for the secret lemon message? (a) a battery cell (b) white paper (c) lemon juice (d) an adult with an iron
4. 4.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) letting the paper dry (c) putting the iron away (d) plugging in the iron
5. 5.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) almost nothing (c) dark brown words (d) blue words
6. 6.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) it gets darker (d) writing stays faint
7. 7.True or false: ironing the paper is a job for an adult. (a) False (b) True
8. 8.True or false: cutting the lemon is a job a child can do. (a) True (b) False
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a cotton bud (c) white paper (d) lemon juice
10. 10.🍋 Which of these steps is a job a child can do? (a) writing the message (b) plugging in the iron (c) ironing the paper (d) cutting the lemon
11. 11.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
12. 12.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
13. 13.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) an adult with an iron (c) lemon juice (d) a balloon
14. 14.🍋 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
15. 15.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) the iron setting (c) how dark the writing is (d) the kind of juice
17. 17.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) white paper (c) lemon juice (d) a cotton bud
18. 18.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
19. 19.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
20. 20.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) reading the message (d) plugging in the iron
21. 21.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the iron is brown (c) the juice scorches first (d) paper turns lemony
22. 22.🔍 Which is the odd one out? (a) reading the message (b) dipping the cotton bud (c) writing the message (d) plugging in the iron
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) True (b) False
24. 24.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) turmeric powder (c) lemon juice (d) a cotton bud
25. 25.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
26. 26.True or false: letting the paper dry is a job for an adult. (a) True (b) False
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) yeast (d) an adult with an iron
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we measure it (c) we change it
29. 29.⚖️ 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
30. 30.⚖️ 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 same paper (c) the kind of juice
31. 31.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) dipping the cotton bud (c) cutting the lemon (d) ironing the paper
32. 32.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
33. 33.True or false: turmeric powder is needed for the secret lemon message. (a) False (b) True
34. 34.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
35. 35.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
36. 36.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) no, it stays brown (c) yes, in the dark (d) yes, if cooled
37. 37.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) chemical (d) physical
38. 38.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we keep it the same (c) we measure it
40. 40.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a small bowl (c) a mirror (d) white paper

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