Invisible Ink Experiment Worksheet

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

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