Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 534 · 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) dry juice is see-through (b) the ink is magnetic (c) the paper ate it (d) it turned into air
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) True (b) False
3. 3.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) plugging in the iron (c) putting the iron away (d) cutting the lemon
4. 4.True or false: reading the message is a job for an adult. (a) False (b) True
5. 5.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
6. 6.⚖️ 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
7. 7.True or false: cutting the lemon is a job for an adult. (a) False (b) True
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) a battery cell (d) lemon juice
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we change it (b) we keep it the same (c) we measure it
10. 10.⚖️ 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) the same cotton bud (c) the ironing time (d) how dark the writing is
11. 11.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
12. 12.True or false: plugging in the iron is a job for an adult. (a) False (b) True
13. 13.⚖️ 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
14. 14.🧺 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 mirror (d) white paper
15. 15.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) plugging in the iron (c) writing the message (d) cutting the lemon
16. 16.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
17. 17.⚖️ 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) True (b) False
18. 18.True or false: yeast is not needed for the secret lemon message. (a) True (b) False
19. 19.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if shaken (c) yes, if cooled (d) no, it stays brown
20. 20.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) it gets darker (d) writing stays faint
21. 21.⚖️ 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
22. 22.True or false: ironing the paper is a job for an adult. (a) True (b) False
23. 23.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a cotton bud (c) a small bowl (d) a magnet
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) False (b) True
25. 25.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we measure it (b) we change it (c) we keep it the same
27. 27.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) paper turns lemony (c) the iron is brown (d) the juice scorches first
28. 28.🔍 Which is the odd one out? (a) putting the iron away (b) ironing the paper (c) cutting the lemon (d) reading the message
29. 29.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
30. 30.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) dipping the cotton bud (c) putting the iron away (d) plugging in the iron
31. 31.🧺 Which of these is not needed for the secret lemon message? (a) a balloon (b) lemon juice (c) white paper (d) a small bowl
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
33. 33.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) blue (d) brown
34. 34.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) a rainbow (c) blue words (d) almost nothing
35. 35.⚖️ 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
36. 36.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) a mirror (c) a magnet (d) turmeric powder
37. 37.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) an adult with an iron (c) lemon juice (d) a small bowl
38. 38.🍋 Which of these steps is a job for an adult? (a) reading the message (b) dipping the cotton bud (c) plugging in the iron (d) letting the paper dry
39. 39.🧺 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 small bowl (d) a magnet
40. 40.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it can burn skin (c) it is magnetic (d) it is cold

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