Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 905 · 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? Which of these is kept the same? (a) the iron setting (b) the kind of juice (c) how dark the writing is
2. 2.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) brown (c) green (d) white
3. 3.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) an adult with an iron (c) a small bowl (d) yeast
4. 4.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
5. 5.⚖️ 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
6. 6.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
7. 7.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) almost nothing (c) a rainbow (d) blue words
8. 8.⚖️ 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 measure it (c) we keep it the same
9. 9.⚖️ 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
10. 10.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
11. 11.🔍 Which is the odd one out? (a) ironing the paper (b) reading the message (c) writing the message (d) dipping the cotton bud
12. 12.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) dry juice is see-through (c) the ink is magnetic (d) the paper ate it
13. 13.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
14. 14.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a battery cell (c) a cotton bud (d) a magnet
15. 15.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a magnet (c) white paper (d) yeast
16. 16.⚖️ 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
17. 17.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
18. 18.True or false: white paper is needed for the secret lemon message. (a) False (b) True
19. 19.True or false: reading the message is a job for an adult. (a) True (b) False
20. 20.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) an adult with an iron (c) a cotton bud (d) a battery cell
21. 21.🔍 Which is the odd one out? (a) cutting the lemon (b) dipping the cotton bud (c) plugging in the iron (d) ironing the paper
22. 22.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) musical (d) chemical
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we keep it the same (c) we change it
24. 24.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
25. 25.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
26. 26.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if cooled (c) yes, in the dark (d) yes, if shaken
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) an adult with an iron (c) lemon juice (d) a battery cell
28. 28.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
29. 29.🍋 Which of these steps is a job a child can do? (a) reading the message (b) ironing the paper (c) plugging in the iron (d) cutting the lemon
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) how dark the writing is (b) the iron setting (c) the kind of juice (d) the ironing time
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we keep it the same (c) we change it
32. 32.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
33. 33.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
34. 34.True or false: writing the message is a job for an adult. (a) True (b) False
35. 35.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) an adult with an iron (c) white paper (d) turmeric powder
36. 36.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) the juice scorches first (d) paper turns lemony
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) False (b) True
38. 38.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
39. 39.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
40. 40.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it

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