Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 431 · 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) the ink is magnetic (b) the paper ate it (c) it turned into air (d) dry juice is see-through
2. 2.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) yeast (c) white paper (d) a small bowl
3. 3.True or false: cutting the lemon is a job for an adult. (a) True (b) False
4. 4.⚖️ 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 change it (c) we measure it
5. 5.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) white paper (c) lemon juice (d) a small bowl
6. 6.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a cotton bud (c) yeast (d) a balloon
7. 7.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the juice scorches first (c) the iron is brown (d) heat adds colour
8. 8.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) no, it stays brown (c) yes, if cooled (d) yes, if shaken
9. 9.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
10. 10.⚖️ 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 change it (c) we measure it
11. 11.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) a magnet (c) a balloon (d) a battery cell
12. 12.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we measure it (c) we keep it the same
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) turmeric powder (d) an adult with an iron
15. 15.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a magnet (c) a cotton bud (d) a small bowl
16. 16.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) turmeric powder (c) an adult with an iron (d) yeast
17. 17.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) lemon juice (c) a balloon (d) white paper
18. 18.🔮 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
19. 19.🔍 Which is the odd one out? (a) cutting the lemon (b) writing the message (c) reading the message (d) letting the paper dry
20. 20.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) the paper floats (d) writing turns green
21. 21.⚖️ 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
22. 22.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
23. 23.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
24. 24.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a battery cell (c) a mirror (d) a small bowl
25. 25.⚖️ 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
26. 26.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
27. 27.⚖️ 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
28. 28.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) plugging in the iron (c) reading the message (d) letting the paper dry
29. 29.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
30. 30.⚖️ 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) True (b) False
31. 31.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) writing the message (c) putting the iron away (d) plugging in the iron
32. 32.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) lemon juice (c) a small bowl (d) turmeric powder
34. 34.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
35. 35.🍋 Which of these steps is a job for an adult? (a) writing the message (b) letting the paper dry (c) ironing the paper (d) dipping the cotton bud
36. 36.True or false: writing the message is a job for an adult. (a) False (b) True
37. 37.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) wash your hands (c) skip washing (d) lick your fingers
38. 38.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) whoever is fastest (c) the youngest child (d) any child
39. 39.True or false: letting the paper dry is a job a child can do. (a) True (b) False
40. 40.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it can burn skin (c) it is magnetic (d) it is sticky

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