Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 806 · 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 cotton bud”? (a) we keep it the same (b) we measure it (c) we change it
2. 2.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) putting the iron away (c) reading the message (d) writing the message
3. 3.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
4. 4.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) a balloon (c) a mirror (d) a magnet
5. 5.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) blue (c) brown (d) white
6. 6.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
7. 7.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) writing the message (c) reading the message (d) ironing the paper
8. 8.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the paper ate it (c) the ink is magnetic (d) dry juice is see-through
9. 9.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
10. 10.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) writing turns green (d) the paper floats
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a balloon (c) lemon juice (d) white paper
12. 12.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
13. 13.True or false: writing the message is a job a child can do. (a) True (b) False
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we measure it (b) we change it (c) we keep it the same
15. 15.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) lemon juice (c) a balloon (d) white paper
16. 16.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) writing the message (d) ironing the paper
17. 17.True or false: ironing the paper is a job for an adult. (a) False (b) True
18. 18.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) ironing the paper (d) dipping the cotton bud
19. 19.🔮 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
20. 20.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) writing the message (c) dipping the cotton bud (d) cutting the lemon
21. 21.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
22. 22.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) turmeric powder (c) an adult with an iron (d) yeast
23. 23.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
24. 24.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) lemon juice (c) a magnet (d) a cotton bud
25. 25.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) plugging in the iron (c) cutting the lemon (d) writing the message
26. 26.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) white paper (c) a small bowl (d) lemon juice
27. 27.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) paper turns lemony (d) the juice scorches first
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a magnet (c) a cotton bud (d) an adult with an iron
29. 29.True or false: cutting the lemon is a job for an adult. (a) True (b) False
30. 30.⚖️ 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
31. 31.🍋 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) ironing the paper
32. 32.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) whoever is fastest (d) only an adult
33. 33.⚖️ 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
34. 34.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
35. 35.⚖️ 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 measure it (c) we change it
36. 36.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
37. 37.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
38. 38.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
39. 39.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) magnetic (c) musical (d) physical
40. 40.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True

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