Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 188 · 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.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) white paper (c) lemon juice (d) a cotton bud
2. 2.🧺 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) lemon juice
3. 3.🍋 Which of these steps is a job a child can do? (a) reading the message (b) cutting the lemon (c) plugging in the iron (d) putting the iron away
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we change it (c) we keep it the same
5. 5.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) paper turns lemony (d) the juice scorches first
6. 6.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a balloon (c) turmeric powder (d) an adult with an iron
7. 7.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
8. 8.⚖️ 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
9. 9.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if shaken (c) no, it stays brown (d) yes, if cooled
10. 10.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) it turned into air (c) the ink is magnetic (d) dry juice is see-through
11. 11.🔍 Which is the odd one out? (a) letting the paper dry (b) ironing the paper (c) dipping the cotton bud (d) reading the message
12. 12.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
13. 13.⚖️ 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
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we change it (c) we measure it
15. 15.⚖️ 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
16. 16.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
17. 17.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) a rainbow (c) dark brown words (d) almost nothing
18. 18.🔍 Which is the odd one out? (a) ironing the paper (b) dipping the cotton bud (c) putting the iron away (d) cutting the lemon
19. 19.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a battery cell (c) a small bowl (d) an adult with an iron
21. 21.True or false: reading the message is a job for an adult. (a) False (b) True
22. 22.⚖️ 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 kind of juice (c) the iron setting (d) how dark the writing is
23. 23.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) an adult with an iron (d) a mirror
24. 24.True or false: cutting the lemon is a job a child can do. (a) True (b) False
25. 25.True or false: plugging in the iron is a job a child can do. (a) False (b) True
26. 26.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
27. 27.True or false: an adult with an iron is needed for the secret lemon message. (a) True (b) False
28. 28.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) any child (c) the youngest child (d) whoever is fastest
29. 29.🔍 Which is the odd one out? (a) ironing the paper (b) plugging in the iron (c) putting the iron away (d) reading the message
30. 30.⚖️ 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
31. 31.True or false: putting the iron away is a job for an adult. (a) False (b) True
32. 32.🍋 Which of these steps is a job for an adult? (a) reading the message (b) dipping the cotton bud (c) cutting the lemon (d) writing the message
33. 33.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is cold (c) it is sticky (d) it can burn skin
34. 34.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) writing turns green (d) the paper floats
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) how dark the writing is (c) the same paper (d) the ironing time
36. 36.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
37. 37.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
38. 38.🔍 Which is the odd one out? (a) letting the paper dry (b) plugging in the iron (c) dipping the cotton bud (d) writing the message
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 change it (b) we measure it (c) we keep it the same
40. 40.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) plugging in the iron (c) letting the paper dry (d) putting the iron away

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