Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 120 · 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 “how dark the writing is”? (a) we change it (b) we keep it the same (c) we measure it
2. 2.True or false: writing the message is a job for an adult. (a) False (b) True
3. 3.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) writing turns green (c) it gets darker (d) the paper floats
4. 4.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) chemical (d) physical
5. 5.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) white paper (c) yeast (d) a cotton bud
6. 6.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
7. 7.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
8. 8.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
9. 9.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) False (b) True
11. 11.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) ironing the paper (c) writing the message (d) cutting the lemon
12. 12.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
13. 13.🍋 Which of these steps is a job for an adult? (a) reading the message (b) letting the paper dry (c) dipping the cotton bud (d) putting the iron away
14. 14.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) reading the message (c) ironing the paper (d) plugging in the iron
15. 15.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) skip washing (c) rub your eyes (d) wash your hands
16. 16.⚖️ 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
17. 17.⚖️ 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 change it (c) we measure it
18. 18.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) ironing the paper (d) writing the message
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) the same cotton bud (c) how dark the writing is (d) the kind of juice
20. 20.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) turmeric powder (c) a mirror (d) a cotton bud
21. 21.True or false: cutting the lemon is a job for an adult. (a) True (b) False
22. 22.🍋 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) dipping the cotton bud
23. 23.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) turmeric powder (c) an adult with an iron (d) lemon juice
24. 24.True or false: reading the message is a job for an adult. (a) False (b) True
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we measure it (c) we change it
26. 26.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
27. 27.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
28. 28.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) paper turns lemony (c) the iron is brown (d) heat adds colour
29. 29.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
30. 30.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) brown (d) blue
31. 31.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is cold (c) it is sticky (d) it can burn skin
32. 32.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) no, it stays brown (c) yes, if shaken (d) yes, in the dark
33. 33.🔮 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
34. 34.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) lemon juice (c) a magnet (d) an adult with an iron
35. 35.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) an adult with an iron (c) a battery cell (d) lemon juice
36. 36.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) white paper (c) yeast (d) a battery cell
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) the same cotton bud (c) the iron setting (d) the kind of juice
38. 38.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) ironing the paper (d) putting the iron away
39. 39.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True
40. 40.True or false: a magnet is not needed for the secret lemon message. (a) True (b) False

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