Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 108 · 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: plugging in the iron is a job a child can do. (a) True (b) False
2. 2.True or false: an adult with an iron is needed for the secret lemon message. (a) True (b) False
3. 3.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
4. 4.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
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.⚖️ 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
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we keep it the same (c) we change it
8. 8.🔍 Which is the odd one out? (a) writing the message (b) letting the paper dry (c) dipping the cotton bud (d) putting the iron away
9. 9.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) reading the message (d) cutting the lemon
10. 10.🍋 Which of these steps is a job for an adult? (a) writing the message (b) ironing the paper (c) letting the paper dry (d) reading the message
11. 11.🍋 Which of these steps is a job a child can do? (a) dipping the cotton bud (b) plugging in the iron (c) ironing the paper (d) cutting the lemon
12. 12.🔍 Which is the odd one out? (a) plugging in the iron (b) writing the message (c) cutting the lemon (d) putting the iron away
13. 13.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we measure it (c) we keep it the same
15. 15.True or false: ironing the paper is a job for an adult. (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) turmeric powder (c) an adult with an iron (d) lemon juice
17. 17.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) magnetic (d) chemical
18. 18.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
19. 19.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
20. 20.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
21. 21.True or false: yeast is needed for the secret lemon message. (a) True (b) False
22. 22.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
23. 23.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is magnetic (c) it can burn skin (d) it is sticky
24. 24.🔍 Which is the odd one out? (a) writing the message (b) dipping the cotton bud (c) letting the paper dry (d) plugging in the iron
25. 25.⚖️ 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 measure it (c) we change it
26. 26.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
27. 27.🔮 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
28. 28.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a balloon (c) an adult with an iron (d) a small bowl
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) True (b) False
30. 30.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) it turned into air (c) the ink is magnetic (d) dry juice is see-through
31. 31.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
32. 32.⚖️ 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 iron setting (c) the kind of juice (d) the same cotton bud
33. 33.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) blue (c) green (d) brown
34. 34.🔮 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
35. 35.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) white paper (d) a mirror
36. 36.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) letting the paper dry (c) reading the message (d) cutting the lemon
37. 37.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) it gets darker (c) writing turns green (d) writing stays faint
38. 38.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
39. 39.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) lemon juice (c) a cotton bud (d) a small bowl
40. 40.True or false: a battery cell is not needed for the secret lemon message. (a) True (b) False

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