Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 521 · 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? What do we do with “the same paper”? (a) we change it (b) we measure it (c) we keep it the same
2. 2.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
3. 3.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) a rainbow (c) dark brown words (d) blue words
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) the kind of juice (c) the ironing time (d) the same cotton bud
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) False (b) True
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) False (b) True
7. 7.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) a mirror (c) a battery cell (d) a magnet
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: the adult irons for only one second. What happens? (a) writing stays faint (b) the paper floats (c) it gets darker (d) writing turns green
10. 10.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) cutting the lemon (d) putting the iron away
11. 11.True or false: putting the iron away is a job a child can do. (a) False (b) True
12. 12.⚖️ 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) False (b) True
13. 13.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) an adult with an iron (c) a battery cell (d) yeast
14. 14.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
15. 15.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
16. 16.True or false: turmeric powder is not needed for the secret lemon message. (a) True (b) False
17. 17.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) dry juice is see-through (c) the paper ate it (d) it turned into air
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we measure it (c) we change it
19. 19.🧺 Which of these is not needed for the secret lemon message? (a) yeast (b) a small bowl (c) a cotton bud (d) white paper
20. 20.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) putting the iron away (d) letting the paper dry
21. 21.True or false: reading the message is a job for an adult. (a) True (b) False
22. 22.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) a magnet (c) turmeric powder (d) yeast
23. 23.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) heat adds colour (d) the juice scorches first
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.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) lemon juice (c) a magnet (d) a cotton bud
26. 26.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) an adult with an iron (c) lemon juice (d) turmeric powder
27. 27.True or false: ironing the paper is a job for an adult. (a) True (b) False
28. 28.⚖️ 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
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we keep it the same (c) we change it
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the iron setting (c) the kind of juice (d) the same cotton bud
31. 31.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it can burn skin (c) it is cold (d) it is magnetic
32. 32.🧺 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) white paper (d) lemon juice
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a small bowl (c) a cotton bud (d) white paper
34. 34.True or false: letting the paper dry is a job for an adult. (a) True (b) False
35. 35.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
36. 36.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
37. 37.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) letting the paper dry (d) writing the message
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
39. 39.True or false: writing the message is a job for an adult. (a) True (b) False
40. 40.🔍 Which is the odd one out? (a) ironing the paper (b) writing the message (c) plugging in the iron (d) putting the iron away

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