Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 520 · 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.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
2. 2.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a cotton bud (c) lemon juice (d) an adult with an iron
3. 3.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a battery cell (c) white paper (d) lemon juice
5. 5.True or false: ironing the paper is a job for an adult. (a) False (b) True
6. 6.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) blue words (c) almost nothing (d) dark brown words
7. 7.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) lemon juice (c) turmeric powder (d) a mirror
8. 8.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) letting the paper dry (d) ironing the paper
9. 9.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
10. 10.🔮 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
11. 11.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) writing the message (d) putting the iron away
12. 12.⚖️ 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
13. 13.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
14. 14.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) ironing the paper (c) plugging in the iron (d) cutting the lemon
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) a cotton bud (c) lemon juice (d) an adult with an iron
17. 17.⚖️ 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) the same paper (c) how dark the writing is
18. 18.⚖️ 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
19. 19.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) an adult with an iron (c) a small bowl (d) white paper
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) True (b) False
21. 21.⚖️ 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) how dark the writing is (d) the same paper
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we change it (c) we measure it
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same cotton bud (b) the same paper (c) the kind of juice (d) the iron setting
24. 24.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the juice scorches first (c) the iron is brown (d) heat adds colour
25. 25.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
26. 26.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) putting the iron away (c) writing the message (d) reading the message
27. 27.⚖️ 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
28. 28.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) physical (d) chemical
29. 29.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
30. 30.⚖️ 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
31. 31.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
32. 32.🔍 Which is the odd one out? (a) reading the message (b) writing the message (c) plugging in the iron (d) dipping the cotton bud
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a small bowl (c) yeast (d) a cotton bud
34. 34.🧺 Which of these is not needed for the secret lemon message? (a) yeast (b) an adult with an iron (c) a cotton bud (d) a small bowl
35. 35.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
36. 36.🔍 Which is the odd one out? (a) writing the message (b) cutting the lemon (c) dipping the cotton bud (d) letting the paper dry
37. 37.True or false: ironing the paper is a job a child can do. (a) True (b) False
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) True (b) False
39. 39.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) blue (d) brown
40. 40.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a battery cell (c) a small bowl (d) white paper

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