Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 925 · 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 what we measure. (a) False (b) True
2. 2.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it can burn skin (d) it is cold
3. 3.True or false: plugging in the iron is a job a child can do. (a) False (b) True
4. 4.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) blue words (c) a rainbow (d) dark brown words
5. 5.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) lemon juice (c) an adult with an iron (d) white paper
6. 6.⚖️ 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
7. 7.🍋 Which of these steps is a job for an adult? (a) reading the message (b) letting the paper dry (c) putting the iron away (d) dipping the cotton bud
8. 8.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) plugging in the iron (c) cutting the lemon (d) dipping the cotton bud
9. 9.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) how dark the writing is (c) the same paper (d) the kind of juice
11. 11.⚖️ 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
12. 12.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) wash your hands (c) skip washing (d) rub your eyes
13. 13.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) reading the message (c) plugging in the iron (d) ironing the paper
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we keep it the same (c) we measure it
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
16. 16.True or false: letting the paper dry is a job a child can do. (a) True (b) False
17. 17.True or false: writing the message is a job a child can do. (a) False (b) True
18. 18.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, in the dark (c) yes, if shaken (d) no, it stays brown
19. 19.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the ink is magnetic (c) it turned into air (d) the paper ate it
20. 20.True or false: letting the paper dry is a job for an adult. (a) True (b) False
21. 21.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) an adult with an iron (c) white paper (d) lemon juice
22. 22.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
23. 23.True or false: putting the iron away is a job a child can do. (a) False (b) True
24. 24.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) paper turns lemony (c) heat adds colour (d) the juice scorches first
25. 25.🔍 Which is the odd one out? (a) plugging in the iron (b) letting the paper dry (c) writing the message (d) dipping the cotton bud
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) the kind of juice (c) how dark the writing is
27. 27.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
28. 28.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
29. 29.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) white paper (c) a balloon (d) yeast
30. 30.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
31. 31.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is the one thing we change. (a) False (b) True
33. 33.True or false: reading the message is a job a child can do. (a) False (b) True
34. 34.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
35. 35.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we change it (c) we measure it
37. 37.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) green (c) white (d) brown
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we keep it the same (c) we measure it
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) True (b) False
40. 40.⚖️ 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 keep it the same (c) we measure it

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