Invisible Ink Experiment Worksheet

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

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