Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 687 · 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.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
2. 2.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) an adult with an iron (c) a magnet (d) lemon juice
3. 3.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
4. 4.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
5. 5.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
6. 6.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we change it (b) we keep it the same (c) we measure it
8. 8.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
9. 9.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
10. 10.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is magnetic (c) it can burn skin (d) it is sticky
11. 11.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
12. 12.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) reading the message (d) cutting the lemon
13. 13.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) physical (d) chemical
14. 14.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a small bowl (c) a balloon (d) lemon juice
15. 15.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, in the dark (c) yes, if shaken (d) yes, if cooled
16. 16.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) putting the iron away (c) writing the message (d) dipping the cotton bud
17. 17.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) lemon juice (c) turmeric powder (d) yeast
18. 18.⚖️ 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 keep it the same (c) we change it
19. 19.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) skip washing (c) lick your fingers (d) rub your eyes
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) an adult with an iron (c) a balloon (d) white paper
21. 21.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a cotton bud (c) a battery cell (d) a small bowl
22. 22.🍋 Which of these steps is a job a child can do? (a) writing the message (b) cutting the lemon (c) putting the iron away (d) ironing the paper
23. 23.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) blue words (c) dark brown words (d) almost nothing
24. 24.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a magnet (c) a small bowl (d) a mirror
25. 25.⚖️ 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 kind of juice (c) the same paper
26. 26.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) heat adds colour (c) paper turns lemony (d) the iron is brown
27. 27.🍋 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
28. 28.True or false: cutting the lemon is a job for an adult. (a) False (b) True
29. 29.True or false: reading the message is a job a child can do. (a) False (b) True
30. 30.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
31. 31.🔮 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
32. 32.⚖️ 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
33. 33.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
34. 34.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) white paper (c) a mirror (d) an adult with an iron
35. 35.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a battery cell (c) a small bowl (d) lemon juice
36. 36.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
37. 37.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
38. 38.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
39. 39.True or false: a magnet is not needed for the secret lemon message. (a) True (b) False
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same cotton bud (b) the kind of juice (c) the ironing time (d) how dark the writing is

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