Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 196 · 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.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) no, it stays brown (c) yes, if cooled (d) yes, in the dark
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) False (b) True
3. 3.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) a magnet (c) turmeric powder (d) a mirror
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) True (b) False
5. 5.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
6. 6.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it is cold (d) it can burn skin
7. 7.⚖️ 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
8. 8.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we measure it (c) we keep it the same
10. 10.🍋 Which of these steps is a job for an adult? (a) cutting the lemon (b) writing the message (c) letting the paper dry (d) reading the message
11. 11.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) almost nothing (c) blue words (d) a rainbow
12. 12.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) reading the message (c) plugging in the iron (d) putting the iron away
13. 13.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) lemon juice (c) a magnet (d) a balloon
14. 14.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) chemical (c) musical (d) physical
15. 15.True or false: plugging in the iron is a job for an adult. (a) False (b) True
16. 16.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a battery cell (c) a cotton bud (d) white paper
17. 17.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
18. 18.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) ironing the paper (c) plugging in the iron (d) dipping the cotton bud
19. 19.🔍 Which is the odd one out? (a) reading the message (b) dipping the cotton bud (c) plugging in the iron (d) writing the message
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) True (b) False
21. 21.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
22. 22.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) the youngest child (d) only an adult
23. 23.True or false: reading the message is a job a child can do. (a) False (b) True
24. 24.🔍 Which is the odd one out? (a) reading the message (b) putting the iron away (c) letting the paper dry (d) dipping the cotton bud
25. 25.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) it gets darker (c) writing turns green (d) the paper floats
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) True (b) False
27. 27.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the ink is magnetic (c) dry juice is see-through (d) the paper ate it
28. 28.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) the juice scorches first (c) paper turns lemony (d) heat adds colour
29. 29.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
30. 30.⚖️ 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 measure it (c) we change it
31. 31.True or false: plugging in the iron is a job a child can do. (a) True (b) False
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.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) True (b) False
34. 34.⚖️ 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 iron setting (c) the kind of juice (d) how dark the writing is
35. 35.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
36. 36.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
37. 37.True or false: writing the message is a job a child can do. (a) False (b) True
38. 38.⚖️ 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 cotton bud (c) the kind of juice
39. 39.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
40. 40.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a battery cell (c) a balloon (d) white paper

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