Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 363 · 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) it turned into air (b) the ink is magnetic (c) the paper ate it (d) dry juice is see-through
2. 2.🔮 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
3. 3.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a balloon (c) an adult with an iron (d) lemon juice
4. 4.🔍 Which is the odd one out? (a) writing the message (b) putting the iron away (c) letting the paper dry (d) dipping the cotton bud
5. 5.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a magnet (c) a cotton bud (d) white paper
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) the same paper (c) how dark the writing is (d) the ironing time
7. 7.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if cooled (c) yes, if shaken (d) no, it stays brown
8. 8.⚖️ 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
9. 9.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) True (b) False
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) True (b) False
12. 12.True or false: reading the message is a job for an adult. (a) False (b) True
13. 13.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) the youngest child (c) only an adult (d) any child
14. 14.🔍 Which is the odd one out? (a) reading the message (b) writing the message (c) letting the paper dry (d) ironing the paper
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we change it (c) we keep it the same
16. 16.True or false: white paper is needed for the secret lemon message. (a) True (b) False
17. 17.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a cotton bud (c) turmeric powder (d) white paper
18. 18.True or false: yeast is needed for the secret lemon message. (a) True (b) False
19. 19.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the juice scorches first (c) the iron is brown (d) paper turns lemony
20. 20.🔍 Which is the odd one out? (a) writing the message (b) plugging in the iron (c) cutting the lemon (d) ironing the paper
21. 21.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
22. 22.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) white paper (c) a battery cell (d) a mirror
23. 23.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
24. 24.⚖️ 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
25. 25.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
26. 26.True or false: plugging in the iron is a job for an adult. (a) False (b) True
27. 27.⚖️ 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
28. 28.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a magnet (c) lemon juice (d) turmeric powder
29. 29.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) physical (d) chemical
30. 30.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a magnet (c) an adult with an iron (d) white paper
31. 31.⚖️ 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) False (b) True
32. 32.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) cutting the lemon (c) plugging in the iron (d) ironing the paper
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) turmeric powder (c) an adult with an iron (d) lemon juice
34. 34.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) a balloon (c) a magnet (d) a battery cell
35. 35.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) dipping the cotton bud (c) plugging in the iron (d) ironing the paper
36. 36.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing stays faint (c) writing turns green (d) it gets darker
37. 37.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a balloon (c) white paper (d) a cotton bud
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice 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) the kind of juice (b) the ironing time (c) how dark the writing is
40. 40.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it is cold (d) it can burn skin

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