Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 603 · 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.True or false: cutting the lemon is a job for an adult. (a) False (b) True
2. 2.⚖️ 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
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) True (b) False
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we measure it (c) we keep it the same
5. 5.🔍 Which is the odd one out? (a) plugging in the iron (b) cutting the lemon (c) ironing the paper (d) dipping the cotton bud
6. 6.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a mirror (c) a cotton bud (d) yeast
7. 7.⚖️ 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
8. 8.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a battery cell (c) lemon juice (d) a mirror
9. 9.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
10. 10.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
11. 11.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is cold (c) it is magnetic (d) it is sticky
12. 12.⚖️ 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 measure it (c) we keep it the same
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) the ironing time (c) how dark the writing is (d) the same paper
14. 14.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) writing turns green (c) the paper floats (d) it gets darker
15. 15.True or false: a magnet is not needed for the secret lemon message. (a) True (b) False
16. 16.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
17. 17.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) musical (c) magnetic (d) physical
18. 18.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) dipping the cotton bud (d) plugging in the iron
19. 19.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a balloon (c) an adult with an iron (d) a battery cell
20. 20.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) no, it stays brown (c) yes, in the dark (d) yes, if shaken
21. 21.⚖️ 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
22. 22.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
23. 23.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) wash your hands (c) lick your fingers (d) rub your eyes
24. 24.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) it turned into air (c) the paper ate it (d) the ink is magnetic
25. 25.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
26. 26.🔍 Which is the odd one out? (a) letting the paper dry (b) ironing the paper (c) cutting the lemon (d) putting the iron away
27. 27.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) lemon juice (c) a cotton bud (d) an adult with an iron
29. 29.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) cutting the lemon (c) plugging in the iron (d) ironing the paper
30. 30.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a magnet (c) yeast (d) a small bowl
31. 31.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
32. 32.True or false: plugging in the iron is a job a child can do. (a) True (b) False
33. 33.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) cutting the lemon (d) letting the paper dry
34. 34.⚖️ 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
35. 35.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) brown (c) green (d) white
36. 36.True or false: white paper is needed for the secret lemon message. (a) True (b) False
37. 37.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a mirror (c) a cotton bud (d) an adult with an iron
38. 38.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
39. 39.True or false: ironing the paper is a job a child can do. (a) True (b) False
40. 40.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True

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