Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 900 · 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.⚖️ 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) False (b) True
2. 2.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is magnetic (c) it is cold (d) it can burn skin
3. 3.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) the iron is brown (c) paper turns lemony (d) heat adds colour
4. 4.🧺 Which of these is not needed for the secret lemon message? (a) a magnet (b) a small bowl (c) a cotton bud (d) white paper
5. 5.⚖️ 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
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) how dark the writing is (c) the same paper (d) the iron setting
7. 7.True or false: writing the message is a job for an adult. (a) True (b) False
8. 8.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) reading the message (c) plugging in the iron (d) writing the message
9. 9.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) a rainbow (c) blue words (d) dark brown words
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.🔍 Which is the odd one out? (a) writing the message (b) dipping the cotton bud (c) reading the message (d) putting the iron away
12. 12.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
13. 13.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) dipping the cotton bud (d) ironing the paper
14. 14.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a magnet (c) lemon juice (d) yeast
15. 15.🔍 Which is the odd one out? (a) ironing the paper (b) reading the message (c) dipping the cotton bud (d) writing the message
16. 16.True or false: cutting the lemon is a job a child can do. (a) True (b) False
17. 17.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) white paper (c) an adult with an iron (d) a balloon
18. 18.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
19. 19.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a balloon (c) lemon juice (d) a cotton bud
20. 20.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
21. 21.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a small bowl (c) a magnet (d) a mirror
22. 22.⚖️ 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 change it (c) we measure it
23. 23.🔮 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
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) True (b) False
25. 25.⚖️ 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) the iron setting (d) the ironing time
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we measure it (b) we change it (c) we keep it the same
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) lemon juice (c) yeast (d) a small bowl
28. 28.🍋 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
29. 29.🛟 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
30. 30.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a small bowl (c) an adult with an iron (d) turmeric powder
31. 31.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
32. 32.🔍 Which is the odd one out? (a) dipping the cotton bud (b) plugging in the iron (c) reading the message (d) writing the message
33. 33.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) writing the message (c) ironing the paper (d) dipping the cotton bud
34. 34.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
35. 35.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if cooled (c) yes, in the dark (d) yes, if shaken
36. 36.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
37. 37.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) putting the iron away (d) writing the message
38. 38.⚖️ 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) how dark the writing is (c) the same paper
39. 39.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the ironing time (b) how dark the writing is (c) the kind of juice

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