Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 81 · 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.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) white paper (c) lemon juice (d) turmeric powder
2. 2.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing stays faint (c) it gets darker (d) writing turns green
3. 3.⚖️ 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 measure it (c) we keep it the same
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) a battery cell (d) lemon juice
5. 5.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) a rainbow (c) dark brown words (d) almost nothing
6. 6.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) lick your fingers (c) wash your hands (d) rub your eyes
7. 7.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) brown (c) white (d) blue
8. 8.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a balloon (c) yeast (d) a small bowl
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) lemon juice (c) a magnet (d) an adult with an iron
10. 10.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a cotton bud (c) white paper (d) a balloon
11. 11.🔍 Which is the odd one out? (a) reading the message (b) writing the message (c) letting the paper dry (d) ironing the paper
12. 12.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) letting the paper dry (c) writing the message (d) cutting the lemon
13. 13.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a magnet (c) a cotton bud (d) an adult with an iron
14. 14.⚖️ 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) False (b) True
15. 15.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) white paper (c) a cotton bud (d) turmeric powder
17. 17.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
18. 18.True or false: letting the paper dry is a job for an adult. (a) True (b) False
19. 19.⚖️ 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) False (b) True
20. 20.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
21. 21.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if shaken (c) yes, if cooled (d) no, it stays brown
22. 22.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
23. 23.True or false: plugging in the iron is a job a child can do. (a) False (b) True
24. 24.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) the ink is magnetic (c) it turned into air (d) dry juice is see-through
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) lemon juice (d) yeast
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the kind of juice (c) the ironing time
27. 27.🔍 Which is the odd one out? (a) reading the message (b) plugging in the iron (c) dipping the cotton bud (d) letting the paper dry
28. 28.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
29. 29.True or false: turmeric powder is needed for the secret lemon message. (a) False (b) True
30. 30.⚖️ 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
31. 31.🍋 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
32. 32.⚖️ 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
33. 33.⚖️ 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 same cotton bud (c) the iron setting (d) the kind of juice
34. 34.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
35. 35.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
36. 36.🔍 Which is the odd one out? (a) reading the message (b) letting the paper dry (c) cutting the lemon (d) dipping the cotton bud
37. 37.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) chemical (d) musical
38. 38.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
39. 39.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
40. 40.🧺 Which of these is not needed for the secret lemon message? (a) a balloon (b) a cotton bud (c) an adult with an iron (d) a small bowl

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