Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 787 · 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.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) putting the iron away (d) reading the message
2. 2.⚖️ 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
3. 3.⚖️ 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
4. 4.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
5. 5.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
6. 6.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) white paper (c) a small bowl (d) a magnet
7. 7.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) white paper (c) yeast (d) a balloon
8. 8.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
9. 9.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) dry juice is see-through (c) the ink is magnetic (d) the paper ate it
10. 10.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) an adult with an iron (c) a mirror (d) a small bowl
11. 11.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
12. 12.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) no, it stays brown (c) yes, if shaken (d) yes, in the dark
13. 13.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) white paper (d) a battery cell
15. 15.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) a small bowl (c) white paper (d) an adult with an iron
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we change it (c) we keep it the same
18. 18.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) lemon juice (c) yeast (d) an adult with an iron
19. 19.True or false: putting the iron away is a job a child can do. (a) False (b) True
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same cotton bud (b) the same paper (c) the iron setting (d) the kind of juice
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) False (b) True
22. 22.⚖️ 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
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) False (b) True
24. 24.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) writing turns green (c) it gets darker (d) the paper floats
25. 25.True or false: a magnet is needed for the secret lemon message. (a) False (b) True
26. 26.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
27. 27.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
28. 28.⚖️ 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) how dark the writing is (c) the kind of juice
29. 29.True or false: cutting the lemon is a job a child can do. (a) True (b) False
30. 30.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) an adult with an iron (c) a small bowl (d) a balloon
31. 31.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) ironing the paper (d) dipping the cotton bud
32. 32.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) turmeric powder (c) a battery cell (d) a mirror
33. 33.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) almost nothing (c) a rainbow (d) dark brown words
34. 34.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
35. 35.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) ironing the paper (c) writing the message (d) reading the message
36. 36.⚖️ 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 iron setting (c) how dark the writing is
37. 37.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) plugging in the iron (d) dipping the cotton bud
38. 38.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) reading the message (c) putting the iron away (d) cutting the lemon
39. 39.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
40. 40.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it

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