Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 848 · 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.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) dark brown words (c) almost nothing (d) blue words
2. 2.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
3. 3.True or false: cutting the lemon is a job for an adult. (a) False (b) True
4. 4.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a small bowl (c) a mirror (d) a battery cell
5. 5.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) chemical (d) magnetic
6. 6.True or false: putting the iron away is a job a child can do. (a) True (b) False
7. 7.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
8. 8.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) an adult with an iron (c) a magnet (d) a small bowl
9. 9.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) the juice scorches first (d) paper turns lemony
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we measure it (b) we change it (c) we keep it the same
11. 11.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we keep it the same (c) we measure it
13. 13.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) turmeric powder (c) a magnet (d) lemon juice
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is the one thing we change. (a) True (b) False
15. 15.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
16. 16.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) writing turns green (d) the paper floats
17. 17.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
18. 18.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
19. 19.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a mirror (c) yeast (d) a cotton bud
20. 20.🔍 Which is the odd one out? (a) letting the paper dry (b) plugging in the iron (c) cutting the lemon (d) putting the iron away
21. 21.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
22. 22.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) brown (d) blue
23. 23.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if shaken (c) yes, if cooled (d) yes, in the dark
24. 24.⚖️ 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) True (b) False
25. 25.True or false: white paper is needed for the secret lemon message. (a) True (b) False
26. 26.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) the paper ate it (c) it turned into air (d) dry juice is see-through
27. 27.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
28. 28.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) an adult with an iron (c) yeast (d) a mirror
29. 29.⚖️ 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 same cotton bud
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we change it (c) we measure it
31. 31.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) an adult with an iron (c) a mirror (d) white paper
32. 32.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
33. 33.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) only an adult (c) whoever is fastest (d) any child
34. 34.⚖️ 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 iron setting (c) how dark the writing is (d) the ironing time
35. 35.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) ironing the paper (d) letting the paper dry
36. 36.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) plugging in the iron (d) dipping the cotton bud
37. 37.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) letting the paper dry (c) writing the message (d) dipping the cotton bud
38. 38.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
39. 39.⚖️ 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
40. 40.⚖️ 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

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